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Previous Colloquia in Physics & Astronomy
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| Trusted Research |
| Sophie O & Alastair W |
National Protective Security Authority |
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15:00, Friday 28 February 2025 | | Physics Seminar Room (Building 46/5081) |
The NPSA is the protective security arm of the Security Service, MI5, and along with organizations such as the National Cyber Security Centre works to tackle security threats including espionage and terrorism.
In this colloquium, government representatives Sophie O and Alastair W will outline the risks to academia emanating from state threat actors, ranging from risks to academics themselves through to risks to their research. This will be followed by an introduction to the Trusted Research advice and guidance, which will provide practical steps on how to mitigate research security risks to protect both yourself and your research.
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| Integrated Photonic Quantum Information Processing |
| Dr Jelmer Renema |
University of Twente & QuiX Quantum |
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14:30, Friday 29 April 2022 | | Physics Seminar Room (Building 46/5081) |
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Quantum photonics is one of the leading approaches to large-scale quantum computing, being one of two technology platforms that has demonstrated a quantum advantage. Integrated optics is a scalable way of creating the large-scale optical systems necessary for quantum photonics. In this talk, Dr Renema will present an overview of efforts on integrated photonic QIP, including the recent quantum advantage experiments, the world's largest quantum photonic processor, and an experiment on quantum-photo-thermodynamics.
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| The Physical Dynamics of Ice Crystal Growth |
| Prof Kenneth Libbrecht |
Caltech |
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14:30, Friday 10 December 2021 | | Virtual Colloquium Series (Online/Teams) |
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The humble snowflake presents a remarkably difficult challenge for scientific analysis, as the seemingly simple process of water vapour freezing into ice yields a rich menagerie of self-assembling morphologies depending on environmental conditions. Physically realistic computational growth models are beginning to show promise, but they cannot yet reproduce even basic laboratory experiments. In large part, this unfortunate situation exists because the ice crystal exhibits a complex surface structure accompanied by highly anisotropic molecular attachment kinetics. Prof Libbrecht will describe the phenomenology of snow crystal growth provided by laboratory measurements along with a new physical model that may finally provide a comprehensive picture of the underlying molecular processes.
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| An Accidental Laser and Why We Study It |
| Dr Jonathan Goldwin |
University of Birmingham |
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14:30, Friday 3 December 2021 | | Virtual Colloquium Series (Online/Teams) |
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The advent of the laser revolutionised atomic physics by providing a light source with the spectral brightness to match the intrinsic lineshapes of unperturbed atoms. The strength of light-matter coupling can be further enhanced via confinement within optical resonators. Dr Goldwin will describe experiments with a laser-cooled gas of potassium atoms trapped within a high-finesse ring cavity. As the in-cavity optical depth increases, the regime of collective strong coupling becomes evident as a normal-mode splitting of the cavity transmission spectrum. As the coupling continues to increase, the gas undergoes a transition to lasing driven solely by the cooling and trapping fields. Random switching is observed between clockwise and anti-clockwise lasing modes as well as a controllable breaking of symmetry between the two directions. Measurements of photon bunching below the lasing threshold show the coherence time can be extended by two orders of magnitude through a combination of gain and dispersion. Surprisingly, most of these observations will be familiar to professional 'laserists', but in the last part of the talk Dr Goldwin will describe plans to open new horizons for active quantum sensing with cold-atom lasers.
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| First Results from the New g-2 Experiment at Fermilab |
| Dr Rebecca Chislett |
University College, London |
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14:30, Friday 26 November 2021 | | Virtual Colloquium Series (Online/Teams) |
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The muon g-2 experiment at Fermilab aims to measure the anomalous magnetic moment of the muon to the unprecedented precision of 140 ppb. The current world's best measurement made at Brookhaven National Laboratory, with a precision of 540 ppb, is at odds with the Standard Model theoretical prediction by 3.7 standard deviations. The new experiment is designed to discover whether this two decade old difference really is a sign of new physics. This talk will discuss how this offers a unique probe into beyond-the-standard-model-physics through the high precision that can be reached both in the theoretical prediction and experimental measurement. Data taking started in 2018 and here Dr Chislett will present the first, highly anticipated result from the first run, with a precision slightly better than the current world's best measurement.
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| Introduction to Geodesy |
| Dr Vicki Smith |
NERC Space Geodesy Facility / British Geological Survey |
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14:30, Friday 4 June 2021 | | Virtual Colloquium Series (Online/Teams) |
Measurements of our planet have been the focus of study since ancient Egyptian times. Nowadays the principal objective is the accurate measurement of the shape, size, orientation in space and gravity field of our planet. In this talk, Dr. Smith will discuss the concept of geodesy and Earth Observation and the reference frames these measurements support, with focus on satellite tracking via laser and the measurement of the local acceleration due to gravity.
Click here to join the colloquium via Teams
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| Electrically Levitated Particles To Test Fundamental Physics |
| Dr James Millen |
King's College, London |
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14:30, Friday 28 May 2021 | | Virtual Colloquium Series (Online/Teams) |
Levitated optomechanics, the control and confinement of dielectric nanoparticles using optical fields, is seen as the most promising route to the study of quantum physics at a macroscopic level. However, light is not free of problems, and experiments are limited by photon recoil and challenging due to weak confinement.
A much older technology exploits electrical fields to confine charged particles. Such 'ion traps' do not impart recoil onto the charged particle, and offer extremely deep and stable trapping. In this talk, Dr Millen will present a 'levitated electromechanical' system, where charged microparticles are both confined, controlled and monitored within electrical circuits. He will outline how this platform is useful for testing fundamental thermodynamic processes, and the prospect for using an all-electrical platform for the generation of macroscopic quantum states and the distribution of entanglement.
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| The Weird World of Quantum Matter |
| Prof Prineha Narang |
Harvard University |
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13:30, Friday 14 May 2021 | | Virtual Colloquium Series (Online/Teams) |
The physics of quantum materials hosts spectacular excited-state and nonequilibrium effects, but many of these phenomena remain challenging to control and, consequently, technologically under-explored. By creating predictive theoretical and computational approaches to study dynamics, decoherence and correlations in quantum matter, the work of Prof Narang's group could enable technologies that are inherently more powerful than their classical counterparts ranging from scalable quantum information processing and networks, to ultra-high efficiency optoelectronic and energy conversion systems.
In this seminar, Prof Narang will present work from her research group on describing, from first principles, the microscopic dynamics, decoherence and optically-excited collective phenomena in quantum matter. The simultaneous contribution of processes that occur on many time and length-scales have remained elusive for state-of-the-art calculations and model Hamiltonian approaches alike, necessitating the development of new methods in computational physics. She will show selected examples of their approach in ab initio design of active defects in quantum materials, and control of collective phenomena to link these active defects. Building on this, in the second part of the seminar, Prof Narang will discuss predictions of linear and nonlinear dynamics and transport in topological semimetals and, finally, an outlook on driving quantum matter far out-of-equilibrium to control the coupled degrees-of-freedom.
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| Vectorial Light Matter Interaction |
| Prof Sonja Franke-Arnold |
University of Glasgow |
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14:30, Friday 7 May 2021 | | Virtual Colloquium Series (Online/Teams) |
Research on complex vector light has seen an explosion in activity over the past decades, powered by technological advances for generating such light, and driven by questions of fundamental science as well as engineering applications. Yet, when it comes to light-matter interaction, we often ignore the role of polarisation. Prof Franke-Arnold will present the methods we use to generate and analyse vector light in her lab, discuss the interplay between vector light, external magnetic fields and atomic vapours, and show her group's latest results of visualising magnetic field alignment with spin aligned atoms.
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| Making a Business from Quantum Computing |
| Dr Richard Murray |
ORCA Computing |
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14:30, Friday 30 April 2021 | | Virtual Colloquium Series (Online/Teams) |
Quantum Computing is all the rage at the moment. Everyone from investors and big corporates alike are keen to learn how to become 'quantum-ready'. This might make you believe that anyone can start a quantum computing company, raise funding and be successful. So is it really that easy?
In this talk, Dr Murray will talk not only about some cool technology — how single photons can be used to perform calculation — but also describe the commercial landscape, what is being promised to investors, what companies are really doing and what it's like to take something highly scientific and unknown and turn it into a business.
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| Aircraft Accident Investigation |
| Mr Afandi Darlington |
Air Accident Investigation Branch |
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14:30, Friday 16 April 2021 | | Virtual Colloquium Series (Online/Teams) |
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Afandi Darlington is a Senior Inspector of Air Accidents with the Air Accident Investigation Branch, which is responsible for the investigation of all civil aircraft accidents and serious incidents within the UK and overseas territories, and is involved in investigations of accidents to British-built, registered or operated civil aircraft; it also provides accident investigation expertise worldwide. Formed in 1915, it is now based in Farnborough, where its facilities include workshops, laboratories and vast storage hangars. Afandi will introduce the role of the AAIB and, through examples from previous aircraft accident investigations, will show how the work of the AAIB contributes to aviation safety.
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| Phonons in Bose-Einstein Condensates as sensors for Fundamental Physics |
| Dr Ivette Fuentes |
University of Nottingham |
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14:00, Tuesday 26 May 2020 | | Virtual Colloquium Series Seminar Room (Online/Teams) |
Quantum sensing, including measurements of the local gravitational field and the detection of dark energy, is usually performed using interferometric techniques. These methods involve quantum systems in spatial superpositions. In particular, in atom interferometry, the atom–atom interactions are negligible and the sensitivity is limited by the available time of flight, which requires large spatial separations or long interferometer arms. Therefore, such detectors cannot be miniaturized without loss in sensitivity.
In this talk, Dr Fuentes will present an alternative which involves using collective excitations produced by atomic collisions in a Bose-Einstein Condensate. This enables interference in the frequency domain, i.e., between modes that are sharp in frequency and delocalized over the whole extension of the system (approximately one millimeter). An advantage of this is that detectors can be miniaturized using on-chip technology. Applications range from gravimetry and the detection of gravitational waves to searches for dark matter and dark energy.
This colloquium will be held via Microsoft Teams; connection details will be advertised shortly.
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| Semiconductor Membrane External Cavity Surface-Emitting Lasers |
| Dr Hermann Kahle |
Tampere University of Technology |
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14:30, Friday 21 February 2020 | | Physics Seminar Room (Building 46/5081) |
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Semiconductor lasers are the most versatile laser technology in existence today. With a large array of materials, and through bandgap engineering, it is possible to produce semiconductor lasers across the visible and well into the IR region. The VECSEL (Vertical External Cavity Surface-Emitting Laser) is a semiconductor laser that adopts the majority of the advantages of the diode laser, while additionally offering class A dynamics, near transform-limited beam spatial profiles, narrow linewidth, and the ability to produce mode-locked pulses in the 100 fs regime. By omitting the DBR mirror in the gain structure growth and operating the gain region instead in the transmission regime, the semiconductor Membrane External Cavity Surface-Emitting Laser (MECSEL) represents a paradigm shift in both heat extraction, and hence power scaling, but also in our ability to reach new wavelengths for semiconductor lasers. In this talk, Dr Kahle will present his group's latest developments in semiconductor MECSELs, especially in the NIR region, and discuss future potential towards broadly tunable gain elements.
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| g-2 of the Muon and Electron: anomalous anomalies |
| Prof Thomas Teubner |
University of Liverpool |
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14:30, Friday 10 January 2020 | | Physics Seminar Room (Building 46/5081) |
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The anomalous magnetic moment of the muon, g-2, has been measured and calculated with very high precision. It is one of few observables which persistently show a deviation between experiment and Standard Model prediction. In this talk the current status of the theory prediction will be reviewed, with emphasis on the hadronic contributions which are the main source of the theoretical uncertainties. The developments on the experimental side and the recently emerged discrepancy for the electron will also be briefly discussed.
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| Assessment of Operational Marine and Space Weather Forecasts at the Met. Office |
| Dr Michael Sharpe |
Met. Office |
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14:30, Friday 13 December 2019 | | Physics Seminar Room (Building 46/5081) |
For over 150 years the Met. Office has issued uninterrupted warnings to seafarers in the waters around the UK. Today its most famous product is the Shipping Forecast which, together with various other forecasts and warnings, is produced on behalf of the Maritime and Coastguard Agency.
By contrast, in 2011 the threat posed by space weather caused it to be added to the Government National Risk Register of Civil Emergencies and the subsequent formation of the Met. Office Space Weather Operations Centre. As part of its remit, MOSWOC produces a twice-daily technical forecast containing 4-day predictions of various solar emissions including Geo-Magnetic Storms, X-ray Flares, Electron and Proton Events.
In this seminar, Dr Sharpe will discuss these forecast types and describe the methodologies used by the systems which undertake their assessment to provide real-time performance feedback to forecasters and longer-term information for managers and customers.
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| Enigma: the unbreakable but broken |
| Mr Alan Watson |
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14:30, Friday 6 December 2019 | | Physics Seminar Room (Building 46/5081) |
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Though the Enigma story is well known, Mr Watson will cover some less familiar aspects: why the machine was developed, how it works, its genius and the sheer enormity of breaking the code. The talk will put the Enigma into perspective with developments at the time with some incredible twists in the story of how and why they were developed. Several different Enigma machines will be on display including an original German machine.
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| Quantum Memories for Scalable Photonics |
| Dr Josh Nunn |
University of Bath |
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14:30, Friday 29 November 2019 | | Physics Seminar Room (Building 46/5081) |
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Photonics is an appealing platform for quantum information processing and communications, but the most exciting applications demand large entangled states which have so far been difficult to create. A possible solution is the use of temporal multiplexing, in which the outputs of succesful quantum operations are stored, and then released on-demand. Here, Dr Nunn will review his group's work towards developing quantum memories that can enable this kind of multiplexing.
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| A Brief History of the Parachute in Peace and War |
| Maj Will Fowler |
Military historian |
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14:30, Friday 22 November 2019 | | Physics Seminar Room (Building 46/5081) |
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This autumn marks a century since pioneer Leslie Irvin made the world's first free-fall parachute descent and founded the Irving Air Chute Company, whose parachutes have saved 100,000 lives. Maj Fowler's talk will begin with Leonardo da Vinci, whose parachute design was demonstrated successfully in 2000, and cover how the parachute has been a life saver as well as a means of delivering troops and equipment into battle. It will also describe types of parachute and parachuting techniques.
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| How to Print a Rainbow |
| Dr Susanne Klein |
University of the West of England |
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14:30, Friday 8 November 2019 | | Physics Seminar Room (Building 46/5081) |
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In the 17th century Isaac Newton demonstrated that white light consists of the superposition of different wavelengths visible as colour on a screen. How colour was perceived by a human observer was explained by the work of Thomas Young and Hermann von Helmholtz who identified three cones in the human eye as responsible for colour perception. James Clerk Maxwell succeeded in capturing colour on black and white film by taking photographs through RGB filters and then projecting the positive slides through the same filters again. On white paper the RGB recordings are usually translated into CMYK prints. Dr Klein will discuss the difficulties in capturing and reproducing true colour using as an example completely analogue photographic methods as used by Sergei Prokudin-Gorsky in the early 20th century and showing how colour perception is affected by the spectrum of the printing inks and the colour of the substrate.
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| The Tragic Destiny of Mileva Marić Einstein |
| Prof Pauline Gagnon |
CERN |
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14:30, Friday 18 October 2019 | | Physics Seminar Room (Building 46/5081) |
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What were Albert Einstein's first wife's contributions to his extraordinary productivity in the first years of his career? The publication of Mileva and Albert's love letters in 1987 first revealed how they had worked together. Two recent publications shed more light on Mileva Marić's life and work. Prof Gagnon will review this evidence in its social and historical context. In this presentation, she will avoid speculation and does not attack Albert Einstein personally, but rather strictly sticks to facts. The audience will be able to decide why such a talented physicist has been so unkindly treated by history.
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| Massive Neutrinos |
| Prof Danny Marfatia |
University of Hawaii |
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14:30, Friday 22 March 2019 | | Physics Seminar Room (Building 46/5081) |
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The discovery that neutrinos have mass has led to a revolution in our understanding of neutrinos. Prof Marfatia will summarize the current status of this understanding, identify the open questions, and describe how they may be answered by an ambitious program of experimentation.
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| The Search for Exotic Superfluid Phases |
| Dr Anna Marchant |
University of Oxford |
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14:30, Friday 15 March 2019 | | Physics Seminar Room (Building 46/5081) |
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Ultracold atomic gases confined in optical lattices have proven to be highly versatile, tunable systems, capable of emulating complex condensed matter problems. One such example is the search for exotic superfluid phases which support both superfluid and magnetic order, analogous to applying a magnetic field to a superconductor. In this talk, Dr Marchant will present progress towards the observation of such an exotic superfluid state and ongoing work in search of experimental signatures of the elusive FFLO phase.
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| The Selection of Materials and Processes for Spacecraft Electronic Assemblies |
| Prof Barrie Dunn |
University of Portsmouth |
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14:30, Friday 1 March 2019 | | Physics Seminar Room (Building 46/5081) |
This lecture is based on experiences gained from working in the space industry. It will contain a wide range of "lessons learned" with a focus on materials technology related to the assembly of spacecraft electronics. Topics will include some suggestions for the management and approval of materials and processes for high reliability assemblies; general materials issues related to electronic boxes and corrosion; wires and cables, solderability, red plague, etc; failure modes and tin whiskers; workmanship related to soldered joints, crimping and wire-wrapping; assessment of printed circuit board suppliers; assessment of surface mount technology lines and finished pcb assemblies for harsh environments; training of operators and inspectors; tead-free control planning; non-destructive testing.
The objective of this lecture is to assist scientists and engineers in their selection of a preferred material or manufacturing process for spacecraft or other high reliability electronic hardware.
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| Bio-Inspired Photonics: from nature to applications |
| Dr Silvia Vignolini |
University of Cambridge |
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14:30, Friday 22 February 2019 | | Physics Seminar Room (Building 46/5081) |
The most brilliant colours in nature are obtained by structuring transparent materials on the scale of the wavelength of visible light. By controlling/designing the dimensions of such nanostructures, it is possible to achieve extremely intense colourations over the entire visible spectrum without using pigments or colorants. Colour obtained through structure, namely structural colour, is widespread in the animal and plant kingdom. Such natural photonic nanostructures are generally synthesised in ambient conditions using a limited range of biopolymers. Given these limitations, an amazing range of optical structures exists: from very ordered photonic structures, to partially disordered, to completely random ones.
In this seminar, Prof Vignolini will introduce some striking example of natural photonic structures and review recent advances to fabricate bio-mimetic photonic structures using the same material as nature. Biomimetic with cellulose-based architectures enables us to fabricate novel photonic structures using low cost materials in ambient conditions. Importantly, it also allows us to understand the biological processes at work during the growth of these structures in plants.
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| Technology Consulting: using physics as an inventor for hire |
| Dr Duncan McBryde |
TTP |
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14:30, Friday 18 January 2019 | | Physics Seminar Room (Building 46/5081) |
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Southampton graduate Duncan McBryde hopes to give some insight into how skills learned in Southampton are sought in industry, and how to get into the sector.
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| Artefact Free Measurement: the redefinition of the international system of units |
| Prof Graham Machin |
National Physical Laboratory |
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14:30, Friday 14 December 2018 | | Physics Seminar Room (Building 46/5081) |
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The international system of units (the SI) – namely the kilogram, the ampere, the kelvin, the metre, the mole, the second and the candela – have served the measurement requirements of the world for many years. Since the inception of the SI a number of the individual unit definitions have evolved to meet advancing measurement needs. However in November 2018 the General Congress of Weights and Measures (CGPM) will meet in Paris to usher in the most fundamental change the SI has ever had. The current semi-classical and partially artefact based unit definitions will give way to new definitions based on a set of fundamental constants with defined values. The objective of the redefinition is to ensure that the SI remains enduringly fit for purpose into the 21st Century and beyond. Prof Machin will introduce the current SI, explain the changes that are being made and their impact on measurement. Emphasis will be given to the changes affecting the kelvin and how the redefinition will open up the possibility of no-drift always-right sensors through the development of practical primary thermometry in the 2020s. The talk will be illustrated with real examples and artefacts.
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| Complex Numbers, Waves, and Metamaterials |
| Dr Simon Horsley |
University of Exeter |
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14:30, Friday 7 December 2018 | | Physics Seminar Room (Building 46/5081) |
It is peculiar that 'imaginary numbers' should appear in physics: there is no imaginary axis on a ruler. But electromagnetic waves are most naturally described as complex functions of position. The complex number is a shorthand for how big the wave is (the amplitude) and where it is going (the phase).
For a long time people have tried to understand how to use materials to control waves. This has recently become more pressing, as new materials (so-called metamaterials) have become available. To understand wave propagation in these materials, complex numbers have again proved very useful. In this talk, Dr Horsley will discuss some old and new applications of complex numbers in wave physics. He will show how to develop methods for designing reflectionless and invisible materials, as well as a new way to understand and design materials where the wave can propagate in only one direction, analogous to the so-called topological insulators of condensed matter physics.
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| Nano-Secrets of Star Formation |
| Dr Helen Fraser |
Open University |
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14:30, Friday 30 November 2018 | | Physics Seminar Room (Building 46/5081) |
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Nano-sized dust grains proliferate in the cold, spare regions of space where stars and planets are forming. Covered by condensed molecular material, dominated by water ice, these nano-factories are the source of chemical complexity as star-and planet-formation progresses, and the seeds of larger bodies that eventually form planets, moons, asteroids and comets. Through a combination of laboratory experiments, theoretical simulations and observations, we are testing how icy grains "stick" and how such processes are impacted by the underlying nano- and meso- structure of water ice.
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| Antarctic OCT |
| Prof Tom Brown |
University of St Andrews |
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14:30, Friday 23 November 2018 | | Physics Seminar Room (Building 46/5081) |
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Optical Coherence Tomography (OCT) is an optical imaging technique that enables high resolution imaging to depths of a few mm in tissue. In this talk, Prof Brown will outline the technique and discuss the trials and tribulations involved in the first Antarctic deployment of an OCT system. He will discuss some of the results obtained and explain why studying Antarctic animals is an important scientific venture. He will also discuss briefly life as a field scientist in Antarctica and what happened when events took a turn for the unexpected!
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| A Menagerie of MOTs |
| Dr Kyle Jarvis |
Imperial College, London |
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14:30, Friday 16 November 2018 | | Physics Seminar Room (Building 46/5081) |
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It is difficult to overstate how important the magneto-optical trap (MOT) has been to the burgeoning of atomic Physics in the 30 years since its first realisation. For much of this time the general consensus among the atomic physics community was that MOTs can only work well when the hyperfine angular momentum of the excited state F' is larger than that of the ground state F, F'=F+1. These 'type-I' MOTs share very similar characteristics and behaviour, are well understood, and have been described in detail long ago. Type-II MOTs have F'≥F and have not been well understood until recently. Dr Jarvis will describe a new kind of magneto-optical trap, the blue-detuned MOT, that dramatically improves the performance of type-II MOTs. The phase space density of the blue-detuned MOT is some 106 times higher than any other type-II MOT reported previously. In addition to this he will describe and explain the working of many new configurations of MOT observed using different hyperfine transitions in 87Rb. This is the MOT menagerie, and its inhabitants possess characteristics that are profoundly different from the common type-I MOT.
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| The Seduction of Curves: catastrophe theory, life drawing and beauty |
| Prof Allan McRobie |
University of Cambridge |
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14:30, Friday 9 November 2018 | | Physics Seminar Room (Building 46/5081) |
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Prof McRobie will explain how the mathematics that underlies his lectures on stability in structural engineering can – perhaps surprisingly – best be learned in the life drawing class. The key is the understanding of curved surfaces, whose features may be described by Rene Thom's Catastrophe Theory. Sharing its title with Allan's book, published recently by Princeton University Press, the talk will wander gently across engineering, the sciences and the arts, always with a focus on curves. It begins with the stability of building columns and oil rigs, and after some excursions into optics and gravitational physics, it enters the trickier arenas of psychology, aesthetics and art, to end beside the deathbed of Salvador Dalí.
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| What Actually Is A Lecture, Anyway? |
| Prof Ross Galloway |
University of Edinburgh |
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14:30, Friday 2 November 2018 | | Physics Seminar Room (Building 46/5081) |
For the last three decades, a major theme in physics education research has been the drive for active learning – a pedagogical shift away from passive transmission and absorption of information and towards thinking, doing, modelling, and constructing. This has resulted in the emergence of a largely binary distinction between 'traditional instruction' and what has variously been termed reformed pedagogy, interactive engagement, or active learning, to mention just a few. In this seminar, Prof Galloway will argue that this dichotomy is unhelpful and not reflective of what actually goes on in real classrooms. While the body of evidence in support of the effectiveness of active learning techniques is now highly compelling, the literature is much less clear on what active learning typically looks like in the classroom. Prof Galloway will present some data from a detailed study of classroom environments to illustrate how and why there is (and should be) still some room for instructor-led 'time for telling'. We will explore some of the nuances of the active and transmissionist perspectives, and establish why, in this post-Google-era, it's still extremely important to know stuff.
Your appreciation of this session will probably be enhanced if you bring a smartphone, tablet, laptop, or other device capable of accessing the internet.
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| A Random Walk in the Wood |
| Dr Dan Ridley-Ellis |
Centre for Wood Science and Technology, Edinburgh Napier University |
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14:30, Friday 26 October 2018 | | Physics Seminar Room (Building 46/5081) |
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This week's talk will be a succession of seemingly unconnected thoughts on trees and timber from one of Europe's experts on guessing the strength of wood.
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| Chemical Warfare: the past, the present and the future |
| Maj Will Fowler |
Military historian |
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14:30, Friday 19 October 2018 | | Physics Seminar Room (Building 46/5081) |
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This talk will cover the history of chemical warfare, from its modern inception in the First World War to the development of nerve agents in Germany, Russia, Britain and the US. Maj Fowler will describe the various types of chemical weapons — lethal or incapacitating, persistent or non-persistent, blister and cyanide-based agents — and examples of protective equipment from the two world wars. He will consider the mixed legacy of Fritz Haber — brilliant chemist or the father of chemical warfare? — and the most recent use of chemical weapons in Syria and Salisbury.
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| Diamond Light Source — the UK's synchrotron radiation source |
| Dr Dave Allan |
Diamond Light Source |
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14:30, Friday 16 March 2018 | | Physics Seminar Room (Building 46/5081) |
Diamond Light Source is the UK's national synchrotron science facility. It represents the most significant investment in scientific infrastructure that the UK has made in the last 50 years and is the world's largest medium-energy synchrotron — a type of circular particle accelerator that accelerates charged particles (electrons) through sequences of magnets to almost the speed of light. As the charged particles travel at relativistic speeds around the accelerator, they produce very intense synchrotron light, predominantly in the X-ray region, that is many millions of times brighter than the light produced from conventional sources and, for example, is around 100 billion times brighter than a standard hospital X-ray machine. Synchrotrons play a key role in the scientific infrastructure of most industrial nations and there are about 70 large synchrotrons around the world. They provide a facility for researchers to carry out a range of experiments requiring these unique light beams. The X rays produced by synchrotrons are crucial for the Life Sciences and drug discovery and they underpin a range of technological advances from the development of fuel cells and batteries to the understanding of engineering materials.
The talk will include a brief history of the UK's contribution to the development of synchrotron radiation as a research tool and how the Diamond Light Source facility was established. An overview will be given on how Diamond operates and some of the areas of scientific research it supports will be discussed.
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| Ultracold Molecules for Quantum Science and Test of Fundamental Physics |
| Dr Mike Tarbutt |
Imperial College, London |
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14:30, Friday 12 January 2018 | | Physics Seminar Room (Building 46/5081) |
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Ultracold molecules can be used to test fundamental physics, simulate many-body quantum systems, process quantum information, and study ultracold chemistry. Dr Tarbutt's experiments capture molecules in a magneto-optical trap, cool them to 50 μK, trap them magnetically, and coherently control their rotational state. He will will present these recent results together with plans to study ultracold collisions, make arrays of interacting molecules, and use ultracold molecules to measure the electron's electric dipole moment.
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| The Challenges and Future of Human Exploration of Space |
| Libby Jackson |
UK Space Agency |
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14:30, Friday 1 December 2017 | | Physics Seminar Room (Building 46/5081) |
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Humans first went into space in 1961, landed on the moon in 1969, and have been be continuously living and working on-board the International Space Station since 2000, but where will we explore next? Will the next footsteps be on the Moon or Mars, and who will they belong to? Libby Jackson, Human Spaceflight and Microgravity Programme Manager at the UK Space Agency, looks at what the future of human space exploration might hold and the challenges that will need to be overcome by the next generation of explorers.
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| Weak Lensing as an Accurate Probe of Cosmology and Much More! |
| Prof Henk Hoekstra |
Leiden University |
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14:30, Friday 24 November 2017 | | Physics Seminar Room (Building 46/5081) |
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Weak lensing by large-scale structure is one of the most promising techniques to learn more about the nature of dark energy by mapping the dark matter distribution in the Universe as a function of distance. Weak lensing has also developed into the main tool to determine cluster masses, critical for their use for cosmology, but can also be used to study the dark matter halos of galaxies. Prof Hoekstra will review the recent progress in this active area of research and discuss the prospects for future projects, such as Euclid.
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| Quantum Imaging |
| Dr Pieter Kok |
University of Sheffield |
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14:00, Friday 17 November 2017 | | Physics Seminar Room (Building 46/5081) |
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Imaging and metrology are central tools in the pursuit of science. Quantum mechanics limits the precision of these tools. In this talk, Dr Kok will explore how we can describe these limitations and determine how we can construct optimal measurements for imaging and metrology. He will introduce the concept of the Fisher information, which captures how much information about a physical quantity is contained in a probability distribution (and deserves a place, he will argue, next to the Boltzmann entropy in the physics curriculum). Using this technique, he will sketch a new method for imaging distant black bodies that is not limited by diffraction, and that can in principle be implemented with current technology.
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| The Antikythera Mechanism and the Mechanical Universe |
| Prof Mike Edmunds |
University of Cardiff |
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14:00, Friday 10 November 2017 | | Physics Seminar Room (Building 46/5081) |
How did our view of the Universe develop? By the mid-Eighteenth Century the world view was of a system constrained by physical laws. These laws, if not entirely understood, showed regularity and could be handled mathematically to provide both explanation and prediction of celestial phenomena. Most of us have at least some hazy idea of the fundamental shift that came through the work of Copernicus, Kepler, Galileo and Newton. The idea of a "Mechanical Universe" tends to be associated with these Sixteenth and Seventeenth Century pioneers. Yet recent investigations based around the Antikythera Mechanism, an ancient Greek artefact from around 100 BC, reinforce a view that the "Mechanical" conception has been around for a much longer time – indeed certainly as far back as the third century BC.
The discovery of the structure and functions of the Antikythera Mechanism by modern imaging methods will be described, and a strong claim (based on literary references) will be made that knowledge of mechanical representations of the Universe was critical in the development of cosmology and philosophy. There is evidence that the technology persisted until its spectacular and rather sudden re-appearance in Western Europe around 1300 AD. From then on it is not hard to chart a path through the astronomical clocks of the 16th Century to Kepler's aim (expressed in a 1605 letter) to "show that the heavenly machine is not a kind of divine, live being, but a kind of clockwork..." But is a mechanical viewpoint still useful in 21st Century physics?
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| The Quantification of Personal Risk |
| Dr Frank Duckworth MBE |
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14:00, Friday 3 November 2017 | | Physics Seminar Room (Building 46/5081) |
In 1997, the Royal Statistical Society was asked by the UK Parliamentary & Scientific Committee to devise a simple way of quantifying new risks to individuals to allow easy comparison with more familiar risks. In a series of articles to enlist the help of RSS members, Dr Duckworth proposed the basis of a simple one-dimensional scale which subsequently received wide publicity in the British press.
Dr Duckworth will describe the structure of the risk scale with examples to show how very different risks may be usefully compared. In particular it will be shown how some of the risks that we as a nation are apparently concerned with are absolutely negligible compared with those to which we are permanently exposed just by living on planet Earth.
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| The Venus Hypothesis |
| Dr Annabel Cartwright |
University of Cardiff |
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14:30, Friday 27 October 2017 | | Physics Seminar Room (Building 46/5081) |
Complex life appeared on Earth during a brief 100 million year long burst around 500 million years ago. All of the 'body plans' that exist on Earth now appeared at that time, and many more appeared and then promptly went extinct.
At the same period, our nearest neighbour, Venus, was violently resurfacing, in an explosive and catastrophic event.
Could these two phenomena be linked? Latest models show that Venus could have been a wet, inhabitable planet before it resurfaced. Dr Cartwright will present the hypothesis that complex life actually travelled from Venus to Earth, showing that this fits the pattern of appearance of complex life very well, as well as explaining curious geological features observed from the same period.
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| The Hubble Space Telescope: 27 years of cosmic discovery |
| Dr Jennifer Wiseman |
NASA Goddard Space Flight Center |
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14:30, Friday 20 October 2017 | | Physics Seminar Room (Building 46/5081) |
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The Hubble Space Telescope is operating at peak scientific capability even 27 years after its launch, thanks to successful astronaut servicing missions and operations that keep the observatory in top condition. Dr Wiseman will review the scientific advancements achieved by Hubble, including some, such as measurement of the Hubble constant, that were planned at its launch and many (e.g. evidence for dark energy, analisis of exoplanet atmospheres) that were never dreamed of. Hubble observations are now helping prepare for the James Watt Space Telescope and other future missions, and contribute critical complementary observations for solar system probes like JUNO and New Horizons.
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| The Perilous Practice of Flying and Applying |
| Sqn Ldr Tony Royle |
Open University |
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14:00, Friday 13 October 2017 | | Physics Seminar Room (Building 46/5081) |
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Aeronautical research in Britain during the early part of the twentieth century was advanced by a decision to allow a number of the nation's finest mathematicians to train as pilots and conduct airborne experiments using full-scale aircraft. Given that many would subsequently perish in flying accidents, what justified the risk?
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| Wavefunction Collapse, Gravity, and Experiments |
| Prof Angelo Bassi |
University of Trieste |
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10:00, Friday 23 June 2017 | | Physics Seminar Room (Building 46/5081) |
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Macroscopic superpositions are predicted by Quantum Theory, but are not part of our experience. One explanation is that the Schrödinger equation is approximately right, and spontaneous collapses of the wave function should also be part of the dynamics. These spontaneous collapses should be "rare" for microscopic systems, so that their quantum properties are left almost unaltered. At the same time, they should become more and more frequent, the larger the object, to the point that macroscopic superpositions are rapidly suppressed. Prof Bassi will briefly review the main features of collapse models, as well as their potential link to gravity. He will then present an update of the most promising ways of testing them, focussing on recent updates from non-interferometric tests and optomechanics.
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| The Power of the Ultra-Cold |
| Prof Wolf von Klitzing |
IESL-FORTH, Crete |
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14:30, Friday 26 May 2017 | | Physics Seminar Room (Building 46/5081) |
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Despite their sometimes complicated internal structure, ultra-cold atoms are now one of the best test-beds for quantum technologies. Over the years, we have acquired an almost incredible level of control over all properties of atoms. Their spin can be controlled with nearly infinite precision. Their electronic state can be manipulated on a time-scale of attoseconds and with a precision of milliHertz. Our ability to trap atoms and cool them into their motional ground state has given rise to an amazing range of devices and applications. Ultra-cold atom devices range from the very small to the very big: from the chip-based atomtronic devices and mm-size matter-wave guides to the 10-km-baseline matter-wave interferometer under construction in France (ELGAR), the satellite based interferometer (STE-QUEST) to the 106-km-baseline gravitational wave detector based on ultra-cold atoms (SAGE). Prof von Klitzing will present an overview of the power of ultra-cold atoms, and an introduction to basic ultra-cold atomic devices and matter-wave interferometers from the very small to the very large.
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| Photonic Strategies for the Study of Synapse Form and Function |
| Prof Nigel Emptage |
University of Oxford |
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14:30, Friday 12 May 2017 | | Physics Seminar Room (Building 46/5081) |
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Since Robert Hooke's Micrographia of insects and cells, optical techniques have cast light on the structure and dynamics of living organisms. High-resolution imaging within living tissue, however, is beyond traditional microscopy, and live-cell neuronal imaging is one of the greatest challenges. Prof Emptage will describe a variety of optical methods that reveal the form and function of living synapses. High-resolution fluorescence microscopy has elucidated the role of intracellular Ca2+ stores in pre- and post-synaptic compartments, provided the visualization of silent synapse unmasking, and the first description of presynaptic NMDA receptors in the hippocampus. More recently, single molecule tracking has revealed the dynamic nature of post-synaptic receptors at synapses, and dual-wavelength total internal reflection fluorescence microscope has illuminated mechanisms of lysosome fusion in neuronal dendrites. Current projects include fibre-based deep brain imaging in vivo and light-sheet microscopy in mammalian brain slices.
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| Solar Flares: how the Sun relaxes |
| Prof Lyndsay Fletcher |
University of Glasgow |
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14:30, Friday 5 May 2017 | | Physics Seminar Room (Building 46/5081) |
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The outer atmosphere of the Sun is a magnetically-dominated environment. The magnetic field determines the transport, storage and dissipation of energy, particularly in abrupt and impulsive events called solar flares. Solar flares represent the rapid conversion of energy as the magnetically stressed corona relaxes, with magnetic energy going into plasma heating, the KE of accelerated particles and mass motions. Flares are now observed in exquisite detail with imaging and spectroscopy across the electromagnetic spectrum, allowing increasingly meaningful comparisons with detailed theory. In this talk, Prof Fletcher will give a general overview of recent flare observations and the framework in which they are interpreted, before focusing on one aspect of flare physics, namely the need to rapidly transport energy through the corona and accelerate particles, and discuss recent work on models motivated in part by processes in the Earth's magnetosphere.
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| Using Biology, Chemistry and Physics to Understand and Treat Dementia |
| Prof Frank Gunn-Moore |
University of St Andrews |
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14:30, Friday 28 April 2017 | | Physics Seminar Room (Building 46/5081) |
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It is now thought that there are potential 70 different neurodegenerative diseases that cause dementia. To understand and treat these diseases, we need to revaluate much of the central dogma and our approaches. In this talk, Prof Gunn-Moore will explain how my group is utilising all three of the sciences to understand the molecular changes that occur, development of a potential new drug and also the development of novel optic approaches to interrogate the nervous system.
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| Microwave to Optical Signal Transduction using Piezo-Optomechanical Circuits |
| Dr Krishna Balram |
University of Bristol |
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14:30, Friday 24 March 2017 | | Physics Seminar Room (Building 46/5081) |
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The detection of weak signals (down to the single quantum level) is pretty standard at optical frequencies, given the high photon energy compared to kT and the ready availability of single photon detectors. The same cannot be said for the RF and microwave frequency ranges (1-10 GHz) wherein the low photon energy gets swamped by thermal noise in detectors, requiring the use of cryogenic amplifiers. A wide variety of applications ranging from radio astronomy, MRI to radar require weak RF signal detection and are limited by the detector sensitivity. An alternative approach is to transduce the signals from the RF to the optical domain and use sensitive optical detection. Such an efficient RF-to-optical transducer becomes paramount if distant systems need to communicate with each other using low loss telecom fibres. Both classical (e.g. radio over fibre systems) and quantum (e.g. linking two superconducting qubits in distant dilution fridges) information processing systems will benefit greatly from the development of an efficient microwave to optical signal transducer.
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| Exploring Many-Body Dynamics and Entanglement in Quantum Simulators |
| Prof Andrew Daley |
University of Strathclyde |
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14:30, Friday 17 March 2017 | | Physics Seminar Room (Building 46/5081) |
Over the last two decades, experiments with ultracold atoms and molecules have developed to a level where we have strongly interacting quantum gases that are controllable and measurable on a single-particle level. This now allows us to engineer a range of fundamental models from solid state physics in experiments, and explore their properties cleanly on a microscopic level. Beyond textbook demonstrations of equilibrium and single-particle properties (e.g., insulating phases, magnetic superexchange, and Bloch oscillations), this now enables us to explore fundamental aspects of non-equilibrium dynamics in quantum many-particle systems. These range from the approach of systems to equilibrium and thermalisation in statistical mechanics, to the influence of the environment and decoherence in open many-body quantum systems.
Prof Daley will give an overview of recent developments in these areas, especially illustrating the new possibilities by discussing the recent measurement of many-body entanglement in itinerant particles with ultracold atoms in optical lattices.
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| The History and Physics of Explosives |
| Maj Will Fowler |
Military historian |
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14:30, Friday 17 February 2017 | | Physics Seminar Room (Building 46/5081) |
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From the combination of sulphur, charcoal and saltpetre for 9th century fireworks in China, through the invention of dynamite and gelignite by - and subsequent angst of - Alfred Nobel, to Charles Munroe's discovery of shaped charges, the history of explosives has been colourful and fascinating. No less interesting is the combination of chemistry and physics behind their operation. Maj Fowler will outline the story of explosives, their development and use for both military and non-military applications, while explaining some of the science of how different explosives burn and the different characteristics and uses to which they may be put.
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| Hot Stuff: from materials science to sustainability |
| Dr Sharon George |
Keele University |
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14:30, Friday 10 February 2017 | | Physics Seminar Room (Building 46/5081) |
In order to reach temperatures of over 1600°C gas burners in the glass melting tank use air that is preheated from outgoing waste gas. This efficient method uses stacks of corrosion-resistant refractory bricks, however, high velocities of abrasive material, steep alternating temperature gradients causing thermal shock and aggressive chemical conditions can result in material failure causing the collapse of the whole stack. A range of post-mortem studies of failed aluminium zirconium silicate checker-bricks, including spectroscopic and microscopic analysis on failed materials, reveals the failure mechanism. The project raises important questions about designing for longevity of material, high temperature manufacture and energy conservation.
This basis of industrially-focussed research in combustion technology and product development laid the foundation for a career in technology transfer and later into research in high temperature applications and technology development. Research and teaching areas now include renewable energy development and intelligent design linking to Keele University's new Smart Energy Network Demonstrator.
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| The Watched Pot: Continuous Quantum Measurement |
| Prof Jason Ralph |
University of Liverpool |
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14:30, Friday 13 January 2017 | | Physics Seminar Room (Building 46/5081) |
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Prof Ralph will review the development of continuous quantum measurement models and their application to recent experimental systems in quantum information processing. He will discuss the origins of continuous measurement approaches to the quantum measurement problem from the 'watched pot' quantum Zeno effect and models for decoherence, to modern quantum trajectory methods and quantum state estimation. He will then discuss how such techniques could be used to explore new physics: including nano-optomechanical systems, the quantum-classical interface in chaotic systems, and multi-parameter Hamiltonian estimation problems.
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| Nano-Optomechanics: from cavities to quantum emitters |
| Dr Ignacio Wilson-Rae |
University of York |
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14:30, Friday 16 December 2016 | | Physics Seminar Room (Building 46/5081) |
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Recent years have witnessed an explosion of activity in the emerging field of optomechanics which aims at controlling the motional state of mechanical resonators by optical means. Optomechanical systems seem ideal for testing notions of how our macroscopic "classical world", where quantum superpositions seem to be absent, can be reconciled with quantum mechanics. However, typical schemes, based on light forces in optical cavities, are seriously limited by the smallness of the resulting interaction between single phonons and photons. In this seminar Dr Wilson-Rae will discuss an alternative approach, based on the optical excitation of quantum emitters embedded in nanomechanical structures and their strong electron-phonon interactions. More specifically, he will present theoretical analyses of schemes based on excitons in suspended carbon-nanotubes that: (i) provide direct evidence of nanomechanical energy quantization via the detection of phonon quantum jumps and (ii) allow to explore strong-coupling phenomena in quantum decoherence.
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| Practical Lensless Imaging for Soft X-Ray and Nonlinear Microscopy |
| Dr Bill Brocklesby |
University of Southampton |
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14:30, Friday 9 December 2016 | | Physics Seminar Room (Building 46/5081) |
Imaging has always driven developments in science. The ability to see complex structures has inspired new understanding, from the work of Hooke and van Leeuwenhoek, via X-ray imaging & crystallography, electron microscopy, computed tomography, up to the Nobel-winning subwavelength imaging of Betzig, Hell and Moerner. Yet, despite the advent of the laser and nonlinear techniques such as CARS and STED, these methods still rely on microscopes whose illumination, sample and objective lens design would have been recognizable to Hooke.
Dr Brocklesby will describe a very different kind of microscopy, based on an imaging technique developed over the last 10 years, which bridges between traditional imaging and diffraction measurements (e.g. X-ray scattering). Instead of using lenses to form images, lensless coherent imaging involves illuminating the object with coherent radiation, and measuring the intensity of scattered radiation from the object directly, using no additional imaging optics. The phase information needed to form an image is then reconstructed using an iterative algorithm, yielding the full radiation field at the object, with both its real and imaginary components. Examples include the lab-based soft X-ray microscopy of biological structures with sub 50 nm resolution using a source of coherent femtosecond X-rays, and the first demonstration of non-linear lensless microscopy, allowing direct imaging of the phase of the nonlinear coefficient of periodically-poled lithium niobate (PPLN).
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| Directed Assembly of Active Colloids |
| Prof Mike Cates |
University of Cambridge |
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14:30, Friday 2 December 2016 | | Physics Seminar Room (Building 46/5081) |
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Self-propelled colloidal objects, such as motile bacteria or synthetic microswimmers, have microscopically irreversible individual dynamics. The incoherent behavior of individual swimmers can be harnessed (or "rectified") by microfluidic devices that create systematic motions that are impossible in equilibrium. Prof Cates will present a conceptual and computational proof-of-concept study showing that such active rectification devices could be created directly from an unstructured "primordial soup" of light-controlled self-propelled particles, solely by using spatially modulated illumination to control their local propulsion speed.
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| In Touch with the Nanoworld: trapping nanoparticles and molecular motors |
| Dr Maria Dienerowitz |
Universitätsklinikum Jena |
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14:30, Friday 25 November 2016 | | Physics Seminar Room (Building 46/5081) |
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Brownian motion governs the movement of nanoscopic objects. Trapping metal nanoparticles and molecular motors confines their Brownian motion to a small trapping volume, allowing us to study their dynamic behaviour for extended periods of time. Optical tweezers are fantastic tools to turn metal nanoparticles into nanoscopic sensors that can be positioned non-invasively in 3 dimensions. This talk will focus on their plasmon resonance and the resulting wavelength dependence of the optical forces induced by the trapping laser. The second part of this talk addresses the challenging task to trap sub-100nm transparent objects that are too small to be held with optical tweezers. Dr. Dienerowitz employs an Anti-Brownian-ELektrokinetic trap (ABELtrap) to hold individual F0F1-ATP synthase proteins in solution. This trap facilitates observing the conformational dynamics of this membrane-bound rotary motor protein with single-molecule FRET.
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| Opening Up Another Gravitational Window On The Universe: the LISA low-frequency gravitational wave mission |
| Prof Tim Sumner |
Imperial College, London |
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14:30, Friday 18 November 2016 | | Physics Seminar Room (Building 46/5081) |
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ESA has adopted 'The Gravitational Universe' as the science theme for its L3 mission which will be launched in the time frame 2029-2034. With the resounding success of the LISA Pathfinder mission, and the re-entry of NASA, the most likely mission scenario is LISA-like. The LISA Pathfinder results will be summarised and the consequent LISA science capabilities will be described. The mission timeline and technologies will be outlined.
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| Physics with Antiprotons and Antihydrogen |
| Prof Dirk van der Werf |
University of Swansea |
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14:30, Friday 4 November 2016 | | Physics Seminar Room (Building 46/5081) |
Since the mid 1980, when CERN started to produce relatively low energy antiprotons, considerable progress has been made in the trapping and manipulation of these antiparticles. Presently. seven collaborations are using/planning to use the antiprotons, mainly in fundamental studies. For example, a measurement of antiproton to proton charge to mass ratio has been performed, antiprotonic helium has been used to measure the antiproton to electron mass ratio, and antiprotons are employed, together with positrons, to form antihydrogen. In the last case, the internal properties of the antiatoms will be compared which that of hydrogen, testing CPT. Moreover, a number of collaborations are planning to measure the gravitational acceleration of antimatter using antihydogen.
In this talk a short overview will be given on the present status of the antiproton/antihydrogen field, including the recent results of measurements on magnetically trapped antihydrogen in ALPHA and the future plans for antihydrogen gravity measurements with GBAR.
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| Sun et Lumière: Earth's auroral light-show |
| Dr Steve Milan |
University of Leicester |
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14:30, Friday 28 October 2016 | | Physics Seminar Room (Building 46/5081) |
There is more to the beauty of the Northern Lights, aurora polaris, than meets the eye. They tell of a chain of events that starts at the Sun, stretches through the solar system, circumnavigates the magnetic field of the Earth, and ends in the atmosphere at an altitude of 100 km. The "space weather" that the lights represent has repercussions for everything that relies on space-borne technology.
Although the Earth's magnetosphere can be a dynamic and hostile environment for humans and spacecraft, almost all the activity within it is invisible to us. When we look up at the Sun at midday we are unaware that 65,000 km above our heads is a region of space where the solar wind crashes into our magnetic shield and where twisting and knotting magnetic fields store vast quantities of magnetic energy in our celestial backyard. When looking at the night sky we don't see the huge reservoir of energy – the magnetotail – filling with this magnetic energy and solar wind plasma until it reaches bursting point. Only the auroras bear witness to the deposition of energy and particles in the atmosphere and the reconfiguration of near-Earth space when, every few hours, this stored energy is released suddenly and explosively in a process known as the substorm. And so it is to the auroras we look when we try to understand the complex series of physical processes that mediate the interaction between the solar wind and our planet.
In this lecture, Dr Milan will describe the links of the chain that lead from the Sun to the Earth, and what can be learned about the anatomy of the Earth's magnetic and plasma environment from a study of the auroras and related phenomena.
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| The Future Is Out Of This World |
| Dr Stuart Eves |
Surrey Satellite Technology Limited |
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14:30, Friday 21 October 2016 | | Physics Seminar Room (Building 46/5081) |
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This talk will provide a light-hearted look at how space technology is changing, as satellites become more numerous and sophisticated. Although predicting the future is clearly an imprecise science, some advances in technology are likely to make a significant difference to our lives over the next 20 years, and the talk will endeavour to highlight them.
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| Can't Reason Or Won't Reason? Challenging students to think more deeply about concepts by building models |
| Dr David Sands |
University of Hull |
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14:30, Friday 7 October 2016 | | Physics Seminar Room (Building 46/5081) |
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Trying to work out just what students do when faced with even simple problems is as ongoing area of research In this talk Dr Sands will demonstrate some examples of the difficulties experienced by students: inconsistent thinking, guesswork, faulty reasoning, flawed assumptions, and so on. Dr Sands' approach to this has been to put emphasis on models and modelling. Much of the elements of modelling are well known in the literature, but he will present here a theoretical basis for building models and show how the method can be used in teaching and assessment.
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| A Heterogeneous III-V / Si3N4 Nanophotonic Integration Platform for Chip-Based Nonlinear and Quantum Optics |
| Dr Marcelo Davanco |
NIST |
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14:30, Friday 22 July 2016 | | Physics Seminar Room (Building 46/5081) |
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Current state-of-the-art integrated photonic technology allows the creation of complex circuits that incorporate a great number of functional elements. While such technology has been primarily aimed at classical communications, photonic integrated circuits have recently become very attractive for photonic quantum information, in view of their scalability, stability, and functionality. A recent trend in photonic integration has been heterogeneous integration platforms, in which different types of optical materials are combined and processed on a single substrate. This enables highly optimized devices through specific properties from the individual material types. In this talk, Dr Davanco will report on a heterogeneous photonic integration platform to produce photonic circuits, based on Si3N4 waveguides, which incorporate on-chip triggered single-photon sources based on single self-assembled InAs/GaAs quantum dots (QDs). Self-assembled InAs QDs are to date the most promising triggered solid-state single photon sources for quantum information. In counterpoint, Si3N4 waveguides offer low-loss propagation with tailorable dispersion and high Kerr nonlinearities, which can be explored for linear and nonlinear optical signal processing. This integration platform will enable a new class of highly efficient and versatile integrated nonlinear and quantum photonic devices.
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| Phase Locking and Atom Interferometry |
| Dr Andrea Bertoldi |
Institut d'Optique, Bordeaux |
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12:00, Thursday 21 July 2016 | | Physics Seminar Room (Building 46/5081) |
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In atom interferometry the phase evolution of a quantum superposition state is measured with respect to a reference, e.g. implemented with a local oscillatory signal in the case of an atom clock and with the position of a retro-reflector for a Raman atom gravimeter. The projection of the relative phase is measured as a population unbalance on two energetic levels, and the phase can be recovered unambiguously only over a limited interval. Resolving phase wrapping requires to consider the effect of the measurement process on the system and specifically on its quantum coherence. Several solutions to extend the interrogation interval, hence the instrument sensitivity, have been proposed for atomic clocks, clock comparisons and demonstrated in atom interferometry based inertial sensing; they use two or more ensembles interrogated simultaneously to monitor the relative phase evolution at different time scales to avoid phase wraps over a longer interval. Experiments in Bordeaux extended the unambiguous interval to probe the phase evolution of an atomic ensemble using coherence preserving measurements and phase corrections, and demonstrated the phase lock of the clock oscillator to an atomic superposition state. Dr Bertoldi will propose a protocol based on the phase lock to improve atomic clocks limited by local oscillator noise, which is the case of optical clocks, and foresees the application to other atomic interferometers such as inertial sensors.
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| Non-Equilibrium States in Quantum Rotors |
| Dr Benno Meier |
University of Southampton |
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14:30, Friday 24 June 2016 | | Physics Seminar Room (Building 46/5081) |
Molecules or molecular groups that may rotate freely at low temperatures display spin isomerism: the symmetry of their overall wavefunction is conserved and hence a change in symmetry of its rotational part requires a corresponding change in symmetry of its spin part. Relaxation to thermal equilibrium requires an interaction that couples the spatial and spin parts. The absence of such an interaction suppresses any relaxation, and even in dense systems non-equilibrium states may be preserved for many hours. The process of equilibration, referred to as nuclear spin conversion, is well known in nuclear magnetic resonance (NMR), but also affects bulk properties such as the specific heat.
In his talk, Dr Meier will present nuclear magnetic resonance and dielectric studies of nuclear spin conversion in fullerene-encapsulated water, H2O@C60, and the methyl moiety of 4-methyl-pyridine. He will also describe how non-equilibrium spin isomer distributions may be generated in metabolites such as pyruvate by dynamic nuclear polarization.
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| Nature's Palette |
| Dr Michele Thomsen |
Planetary Science Institute, Tucson AZ and Los Alamos NM |
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14:30, Friday 3 June 2016 | | Physics Seminar Room (Building 46/5081) |
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Like an artist's palette, Nature has a set of common physical processes to employ to make a magnetosphere. The nature of a particular work of art depends on how much of each of the colors is used and how they are combined on the canvas, i.e., on the particular talent of the artist. In much the same way, the nature of a magnetosphere is determined by the particular properties of a given planet and how those properties influence the dynamical significance of the various processes. Dr Thomsen will examine some of the processes in Nature's palette and see how their importance varies from magnetosphere to magnetosphere within our own solar system. Comparing actual realizations of magnetospheres to which we have in-situ access enables us to see the interplay between the physical processes and the peculiar conditions of each body. As we contemplate the extra-solar planets we are now discovering, we need to consider other possible combinations of colors from this palette: What other wonderful and exotic magnetospheres might exist throughout the universe?
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| Imaging in Direct and Reciprocal Space at the Diamond Light Source by utilising I13's Unique Coherence Properties |
| Dr Ulrich Wagner |
Diamond Light Source Ltd. |
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14:30, Friday 27 May 2016 | | Physics Seminar Room (Building 46/5081) |
I13 is a 250 m-long hard x-ray beamline (6 keV to 35 keV) at the Diamond Light Source. It comprises two fully independent and simultaneously operating experimental endstations: one for imaging in direct space, currently providing high resolution in-line phase-contrast tomography; and one for imaging in reciprocal space using coherent diffraction based techniques like Ptychography, Bragg-CDI and Photon-Correlation Spectroscopy. In addition, the particular design of this branch provides an outstandingly large lateral coherence length beyond 200um, lending itself to unique research in the field of coherent x-ray optics, the development of novel instrumentation and imaging techniques in relation to interferometry, holography and speckle tracking.
After an overview of the Diamond Light Source and the specifics of synchrotron light, the talk will delineate advances in instrumentation achieved at Diamond, like the Double-Mini Beta Scheme and a new generation of horizontally deflecting beamline optics, entailing the design of I13 and its two endstations. These facilities and the science they support will be adumbrated by discussing some representative experiments in more detail. Eventually the talk will give a short outlook on the future development of I13 towards nano-imaging and the prospects for I13 provided by a machine upgrade towards an ultimate storage ring.
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| Neglected Terms and Hidden Gems in Atom-Light Interaction |
| Dr Matthias Sonnleitner |
University of Glasgow |
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14:30, Friday 20 May 2016 | | Physics Seminar Room (Building 46/5081) |
The mechanical interaction between atoms and laser light is the basis of many modern technologies and a continuous source of fascinating research. Today cold and ultracold atomic clouds can be controlled and manipulated at a level that allows atom opticians to measure the tiniest of forces and, for instance, test fundamental theories on gravity.
Given this success and precision it might be time to look at one of the usually neglected aspects of atom-light interaction, the so-called Roentgen term. In this talk, Dr Sonnleitner will introduce this largely unknown interaction and explain its physical origin. He will then present some surprising theoretical results and discuss possible implications on current experiments.
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| Generation of Mechanical Interference Fringes by Multi-Photon Quantum Measurement |
| Dr Michael Vanner |
University of Oxford |
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14:30, Friday 29 April 2016 | | Physics Seminar Room (Building 46/5081) |
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Quantum optomechanics uses the radiation-pressure interaction and the tools of quantum optics to extend the control of individual quantum systems to a macroscopic regime. The field is currently receiving a surge of interest for its potential to contribute to both fundamental and applied science with current research directions including table-top tests of quantum gravity and the development of high-precision weak-force sensors. In this talk, Dr Vanner will describe some recent experimental work that observed mechanical interference fringes as a key step towards generating non-classical states of motion of a massive mechanical resonator.
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| Quantum Dynamics of Photo-Activated Biomolecules |
| Dr Alexandra Olaya-Castro |
University College, London |
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14:30, Friday 18 March 2016 | | Physics Seminar Room (Building 46/5081) |
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Photosynthesis is the process by which plants, algae and some bacteria use sunlight to initiate the chemical reactions that sustain life processes. It is well known that the primary steps of the photosynthetic process rely on quantum mechanical phenomena. For instance, excitons or the collective absorbing electronic states of light-harvesting biomolecules are a clear manifestation of collective quantum behaviour of the chromophores that form these complexes. However, when it refers to the transfer and conversion of excitation energy in the picosecond time scale, it is not entirely clear which dynamical features can only be predicted within a quantum mechanical framework and how they correlate to the effective energy flow in photosynthetic complexes. In this talk, Dr Olaya-Castro will discuss research shedding light on this issue.
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| Hazards Under the Sea – deep waters don't run still... |
| Dr Mike Clare |
National Oceanography Centre, Southampton |
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14:30, Friday 11 March 2016 | | Physics Seminar Room (Building 46/5081) |
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The ocean makes up 71% of the Earth's surface, yet only 5% has been mapped in detail largely due to the challenge of working in extreme water depths featuring high pressures, zero visibility and limited or no background information. Remarkably we know more about the surface of Mars than our own planet. Despite this large unknown, demands for global energy and communication links push hydrocarbon exploration and seafloor infrastructure into deeper and unchartered waters. To develop in such areas, it necessary to cross slopes that feature a wide array of potentially damaging, but often poorly understood geohazards. In this talk, Dr Clare introduces some of these geohazards, including the largest landslides on the face of our planet that can trigger devastating tsunamis, fast flowing subsea sediment avalanches that that can transport more sediment than all the world's rivers combined, and major earthquake-faults at the contacts of continental plates. New monitoring of geohazards performed by NOC Southampton and collaborators is providing the first direct observations of marine geohazards. Mike will outline how new technology and ongoing research are allowing us to tackle the challenge.
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| Get a Better Photon: shape, sieve, and switch |
| Dr Peter Mosley |
University of Bath |
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14:30, Friday 4 March 2016 | | Physics Seminar Room (Building 46/5081) |
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The development of higher-performance single-photon sources is a pressing issue for photonic quantum information processing, as independent sources are currently unable to provide sufficient numbers of identical single photons simultaneously. Dr Mosley will discuss recent progress in the field of photon-pair sources based on nonlinear optics and present the latest results from the University of Bath. He will describe his group's development of a source incorporating dispersion-engineered photonic crystal fibre, novel filtering techniques, and active switching to generate high-purity heralded photons in an all-fibre architecture.
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| Shackleton's Endurance Expedition 1914-16 – with Hurley's slides and as seen through the eyes of physicist R W James |
| Mr Robert Hollingdale |
Royal Institute of Navigation |
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14:30, Friday 19 February 2016 | | Physics Seminar Room (Building 46/5081) |
100 years ago, Sir Ernest Shackleton's Imperial Trans-Antarctic Expedition was marooned at the improvised 'Patience Camp' on the Weddel Sea ice floe. The Endurance, ice-locked a year earlier, had sunk in November, and the perilous 800 mile rescue voyage of the James Caird would begin only five months later. Shackleton's successful rescue of his entire crew turned the failure into a legend, beautifully illustrated by the glass plates, celluloid images and early film footage of the expedition photographer Frank Hurley.
This talk, using Hurley's slides, will describe the Endurance expedition through the eyes of the expedition physicist R W James – one of four scientists amongst the 28-man crew. After serving as an artillery spotter on the Western Front, James went on to research X-ray crystallography with W L Bragg, was elected a FRS, and became VC of the University of Cape Town.
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| Novel Techniques for Portable Cold Atom Experiments |
| Dr Graham Bruce |
University of St Andrews |
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14:30, Friday 12 February 2016 | | Physics Seminar Room (Building 46/5081) |
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The drive to miniaturise atom-based metrological devices is an important area in modern research. Dr Bruce will report on progress towards realising such a portable setup with three main results: a) a method of determining vacuum pressure using cold atoms, removing the need for a standard vacuum gauge, b) the creation of a portable magneto-optical trap which has been used to demonstrate cold atom physics at public events across Scotland, and c) the development of computer generated holographic techniques for the production of highly flexible and multi-wavelength optical traps with a simple apparatus. Furthermore he will demonstrate the applicability of these holographic traps for two experiments: ring traps for rotation sensing and the creation of a cold atom device that can be used as an investigation of the topological Kondo effect.
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| Introduction to the Physics of Chocolate |
| Ms Isabella Van Damme |
Mars Chocolate |
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14:30, Friday 29 January 2016 | | Physics Seminar Room (Building 46/5081) |
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For most people, chocolate is an irresistible delicious treat. Others see it as an equally irresistible dense suspension of solids in a lipid phase that lends itself to some interesting research. The formation and manipulation of this suspension is key to deliver the smooth, attractive textural attributes of chocolate. This presentation will aim to demonstrate how physics plays an important role in understanding and controlling the properties of chocolate and highlight some of the major research questions.
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| Thermodynamics and Information at the Nanoscale |
| Dr Janet Anders |
University of Exeter |
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14:30, Friday 8 January 2016 | | Physics Seminar Room (Building 46/5081) |
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Einstein realized that the fluctuations of a Brownian particle can be used to ascertain the properties of its environment. In the first part of the talk, Dr Anders will report on a nano-scale thermodynamic experiment with heated optically trapped nanospheres in a dilute gas. By developing a new theoretical model that captures the non-equilibrium situation of the particles, this allowed measurement of the surface temperature of the trapped spheres, and observation of temperature gradients on the nanoscale. Dr Anders will then give a brief overview of quantum thermodynamics theory and discuss the role of coherences and correlations.
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| The Science and Applications of National Nuclear Security |
| Dr Neil Gaspar |
AWE Aldermaston |
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14:30, Friday 11 December 2015 | | Physics Seminar Room (Building 46/5081) |
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Dr Gaspar's talk will address some scientific and technological aspects of the detection and verification of nuclear materials and components.
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| Relativistic Cosmology in the 21st Century |
| Prof Pedro Ferreira |
University of Oxford |
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14:30, Friday 4 December 2015 | | Physics Seminar Room (Building 46/5081) |
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Physical Cosmology is the success story of modern physics. Observations of the large scale structure of the universe have allowed us to characterize the cosmological model with unprecedented precision. What is less appreciated is that we have learnt a great deal about the building blocks of Relativistic Cosmology: about space-time, it origins and the role of general relativity in the evolution of the universe. In this talk, Prof Ferreira will show how, over the last two decades, we have made tremendous progress in characterizing the overall metric of space-time – its homogeneity and isotropy – as well as its properties at very early times. He will show how exploring general relativity can play a crucial role in solving one of the big cosmological puzzles (the dark energy problem) and how cosmology can be used to find new, precision constraints on general relativity. He will discuss a vision of the future in which we attempt to completely map out the large scale characteristics of space-time using innovative techniques and future surveys.
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| Electron Charge and Spin State Readout in Carbon Nanotube Quantum Dots |
| Dr Mark Buitelaar |
University College, London |
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14:30, Friday 27 November 2015 | | Physics Seminar Room (Building 46/5081) |
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Dr Buitelaar will discuss electron charge and spin state readout of carbon nanotube quantum dots which are of interest for solid-state quantum information processing. The first part of the talk will focus on weakly coupled double quantum dots in which certain electron transitions between the dots are forbidden by spin conservation. This is important as it allows us to convert the electron spin degree of freedom to a much easier measurable charge state or current. The second part of the talk will focus on radio-frequency reflectometry as a tool to read out these charge states in a fast and non-invasive way. Dr Buitelaar will describe results for which this technique is combined with microwave spectroscopy to measure charge relaxation and coherence times.
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| Superconducting Single-Photon Detectors |
| Prof Robert Hadfield |
University of Glasgow |
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14:30, Friday 20 November 2015 | | Physics Seminar Room (Building 46/5081) |
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Single photon detectors based on superconducting nanowires have emerged as a highly promising alternative for infrared single photon detection. These devices offer single photon sensitivity from visible to mid infrared wavelengths with high efficiency, low dark count rates and tens of picosecond timing precision. Prof Hadfield will discuss the basic device design, materials considerations, fabrication through electron beam lithography and integration with advanced optical structures. He will also discuss prospects for scale-up from microscopic single pixel devices to large area arrays, and how these low temperature devices can be mounted in practical closed-cycle systems. He will then give an overview of applications where these devices are being deployed, including long distance quantum cryptography, remote sensing, laser medicine and development of optical quantum computing.
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| Ultra Intense Laser Plasma Interactions: physics at the extremes |
| Dr Kate Lancaster |
University of York |
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14:30, Friday 6 November 2015 | | Physics Seminar Room (Building 46/5081) |
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Ultra intense lasers are capable of producing some of the most extreme conditions on earth in terms of temperatures, pressures, and electric and magnetic fields. There is a wealth of science that can be uncovered during these interactions that spans from fusion energy to quantum electrodynamics. This talk will give a snap shot of the current state of play of the science possible on these large scale lasers, especially focusing on laser driven fusion energy. The talk will conclude with some predictions about the future of the field and the regimes of science we will be able to access.
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| Supernovae Type Ia as Distance Indicators: successes and pitfalls |
| Dr Roberto Trotta |
Imperial College, London |
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14:30, Friday 30 October 2015 | | Physics Seminar Room (Building 46/5081) |
Supernovae type Ia (SNIa) are one of the observational pillars of the concordance cosmological model, and have been instrumental in determining the existence of dark energy. While the observational effort has been very successful in finding over 1,000 cosmologically useful SNIa's, the sophistication of statistical methods employed to analyse the data and infer cosmological parameters has been lagging behind.
In this talk, Dr Trotta will present an overview of the status of SNIa cosmology, as well as new results from BAHAMAS (BAyesian HierArchical Modeling for the Analysis of Supernova cosmology), a fully Bayesian analysis of SNIa data, a demonstrably superior approach which improves on many shortcomings of the usual method.
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| Mobility, Fire Power, Protection – squaring the circle of armoured vehicle design |
| Maj Will Fowler |
Military historian |
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14:30, Friday 16 October 2015 | | Physics Seminar Room (Building 46/5081) |
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September 2016 will mark the 100th anniversary of the battle of Flers Courcelette and the first use of tracked armoured vehicles in war. The tarpaulin shrouded shapes were called tanks as a cover as they were moved across France to the Somme and the name stuck. With their introduction the nature of land warfare changed forever. This talk will be a layman's look at the physics behind tank design, mobility and fire power. Few tank designs have managed to combine the three design features in one vehicle and we will look at the challenge this presents.
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| Understanding the Rabi model beyond the rotating-wave approximation |
| Dr Elinor Irish |
University of Southampton |
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14:30, Friday 9 October 2015 | | Physics Seminar Room (Building 46/5081) |
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The Rabi model – a single two-level system interacting with a quantum oscillator – is one of the simplest yet also one of the most enigmatic of quantum models. Recent years have seen a resurgence of interest in the Rabi model, as the drive toward practical quantum technology has produced experiments with capabilities that push the limits of our understanding of the underlying physics. Motivated by both theoretical and experimental considerations, Dr Irish will discuss some of the progress that has been made toward understanding the Rabi model beyond the standard rotating-wave approximation, focusing on the role of unitary transformation techniques. This will not be a heavily mathematical talk, instead emphasising physical intuition and linking theory to experiments.
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| ICE: Atom Interferometry in Microgravity |
| Dr Brynle Barrett |
Institut d'Optique, Université de Bordeaux |
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14:30, Friday 5 June 2015 | | Physics Seminar Room (Building 46/5081) |
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Over the past 20 years, atom interferometers have emerged as ultra-sensitive instruments with applications in both fundamental physics and industry. Their high sensitivity to inertial effects has been utilized to measure, for instance, the gravitational acceleration g, or the rotation rate of the Earth, with unprecedented precision. However, typically atom interferometers are realized in laboratory environments with large, static setups which suffer from a variety of limitations, such as the size of the vacuum system and the corresponding maximum free-fall time of the atoms. It is thought that the full potential of atom interferometers can only be realized in Space, where the atoms are in perfect free-fall with the apparatus. In this talk, Dr Barrett will give an overview of the ICE experiment, which is the first mobile dual-species interferometer in existence. It is capable of operating onboard the Novespace A310 Zero-G aircraft during parabolic flight?the ultimate goal of which is to test the weak equivalence principle in a microgravity environment. This involves precisely measuring the relative acceleration between two atoms with different masses (87Rb and 39K). Dr Barrett will discuss the challenges involved in this work, and conclude with recent experimental results.
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| Experiments with Rydberg Positronium Atoms |
| Dr David Cassidy |
University College, London |
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14:30, Friday 29 May 2015 | | Physics Seminar Room (Building 46/5081) |
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Positronium (Ps) is a metastable atomic system formed from an electron bound to a positron. The ~100 ns lifetime of these atoms does not directly impede spectroscopic investigations of Ps, but the creation of suitable positron sources certainly does. Positron traps have made it possible to produce intense pulses containing up to 107 positrons in a ns burst using weak incident positron beams. These can be used to make a "gas" of positronium which in turn can be probed with pulsed lasers in much the same way as any other atomic species. The ability to create a Ps gas makes feasible hitherto impractical (or impossible) experiments, such as the production of molecular positronium. In this talk, Dr Cassidy will discuss ongoing experiments in which highly excited atomic states of Ps can be created and studied, including Doppler-free 2-photon state-selective production of Rydberg Ps and the production of selected Stark-States in electric fields. The ultimate goal is the electrostatic manipulation of Rydberg Ps with inhomogeneous electric fields to produce Ps "atom-optics" and focus and decelerate Ps atoms, enabling many new experiments, from spectroscopy to gravity measurements.
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| Optically Actuated Micro-Robotics / Imaging Without A Camera |
| Dr Dave Phillips & Dr Matt Edgar |
University of Glasgow |
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14:30, Friday 22 May 2015 | | Physics Seminar Room (Building 46/5081) |
Direct laser writing is a powerful and flexible tool with which to create 3D micro-scale structures with nanoscale features. These structures can then be dispersed in aqueous media and dynamically actuated in three dimensions using optical tweezers. The ability to build, actuate and precisely measure the motion of complex microscopic structures heralds a variety of new applications - optically actuated micro-robotics.
Dr Phillips will describe the design, fabrication of control of these devices, and the real-time 3-D stereomicroscopy of their Brownian motion. Feedback control transforms these structures into quantitative tools, for applications including surface imaging and a new form of hydrodynamic micro-manipulation.
Camera technology has undergone three significant shifts: first from manually to electro-mechanically driven hardware; then from the analogue age of photosensitive chemistry to the digital era of solid-state sensors and storage; and now to the computational age, when computer algorithms and modified hardware (including high-speed MEMS, ultrafast timing circuits, single photon detectors and high-performance computing) can enhance camera operations, overcome their limitations and revolutionize their applications.
Dr Edgar will describe a camera that can take infrared images using a cheap photodiode in place of a costly pixelated sensor, and will cover some current investigations where such a 'single-pixel camera' could have important applications.
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| Flying a constellation of geostationary satellites in the dynamic space environment |
| Dr Mark Dickinson |
Inmarsat |
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14:30, Friday 8 May 2015 | | Physics Seminar Room (Building 46/5081) |
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Inmarsat currently operates a constellation of 11 geostationary telecommunication satellites ranging in age from almost 20 years to only a few months. These satellites provides mobile connectivity on a global basis, typically to ships, aircraft, media, energy sector but also for first responders as seen with the tragic recent events in Nepal. The presentation will touch on the evolution in technology and design principles used for these spacecraft which allows them to operate safely within the highly dynamic space environment. This includes continuous exposure to the galactic cosmic ray flux and also particles originating from the Sun, especially during events such as large coronal mass ejections.
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| Quantum Networks with Ion-Cavity Systems |
| Dr Matthias Keller |
University of Sussex |
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14:30, Friday 1 May 2015 | | Physics Seminar Room (Building 46/5081) |
Trapped ions have recently evolved to be the most successful quantum information processing systems. Several high fidelity quantum gates have been established and quantum algorithms have been implemented. Even though entanglement between up to 14 ions within the same ion trapping potential has been shown, strategies for the scaling up of the number ion qubits is still required. While complex trapping structures with several trapping zones promise an increase of up to 10s of ions, distributing quantum information processing over several nodes in a delocalised network has the potential to increase the number of qubits well beyond 100s of ions. Crucial component for these networks are interfaces between ions and photons acting as 'quantum modems'.
Dr Keller's group investigates ion-cavity systems to serve as quantum interfaces. Exploiting the interaction of ions with the mode of an optical cavity the high fidelity, bidirectional quantum state transfer between photons and ions is feasible. Furthermore, deterministic generation of entanglement between photons and ions as well as between remote ions become possible.
For tight integration of the cavities into the trapping structure and to achieve a strong interaction between ion and cavity, the Sussex group investigates optical fibre tip cavities and novel ion trap designs. In this presentation Dr Keller will give an overview of our experiments and report on the recent progress.
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| Quantum Cascade Lasers: from THz non-linear optics to ultra-short pulse generation |
| Dr Sukhy Dhillon |
Laboratoire Pierre Aigrain, ENS Paris |
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14:30, Friday 20 March 2015 | | Physics Seminar Room (Building 46/5081) |
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The Quantum Cascade Laser is the semiconductor solution to realise laser action over the entire mid-infrared to the terahertz (THz) regions of the electromagnetic spectrum. This wavelength agility arises from the use of intersubband transitions, transitions between confined electronic states within a set of quantum wells. The progress in this field has been rapid from high power and high temperature operation to the recent commercialization of mid-infrared QCLs for high sensitivity trace gas detection. After an overview, Dr Dhillon will present how new functionalities can be introduced using the inherent properties of QCLs. These include THz nonlinear optics by means of the high powers that approach those used in free electron lasers and short pulse generation using the ultrafast carrier dynamics of the gain recovery.
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| A Global Analysis of Erosion and Flooding due to Sea-Level Rise |
| Prof Robert Nicholls |
University of Southampton |
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14:30, Friday 13 March 2015 | | Physics Seminar Room (Building 46/5081) |
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Global sea-level rise has been recognised as a significant hazard for the last 25 years and there has been global-scale concern about the potential for coastal erosion and flooding. This talk will discuss the results on these issues that have been developed, with a strong emphasis on the results developed with the Dynamic Interactive Vulnerability Analysis (DIVA). This shows that both hazards could be significant, with the largest losses being due to coastal flooding. The results also show the importance of adaptation in controlling impacts – considering realistic adaptation reduces impacts dramatically. The potential role of climate mitigation will also be briefly considered.
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| Fundamental Physics with Antihydrogen |
| Dr James Storey |
CERN |
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14:30, Friday 6 March 2015 | | Physics Seminar Room (Building 46/5081) |
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Antihydrogen, the bound state of an antiproton and a positron, was first produced at CERN in 1995 at relativistic energies. Over the past two decades tremendous progress has been made by experiments at CERN's Antiproton Decelerator (AD) facility towards the production of low energy antihydrogen that is compatible with the high precision experimental methods that have been developed for the study of hydrogen. This talk will present an overview of the current antihydrogen experiments at CERN, with particular emphasis on progress towards spectroscopy of antihydrogen with the ALPHA experiment and measuring the gravitational free-fall of antihydrogen with the AEgIS experiment.
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| Adventures in the Outer Solar System |
| Dr Caitriona Jackman |
University of Southampton |
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14:30, Friday 27 February 2015 | | Physics Seminar Room (Building 46/5081) |
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Dr Jackman will take you on a tour of the outer solar system, highlighting the key discoveries that have been made and the biggest questions for future exploration. Results from missions such as Galileo at Jupiter and Cassini at Saturn will highlight the diversity of planetary magnetospheric dynamics as well as the zoo of moons, some of which indicate that they can harbour life. The final portion of the talk will focus on future plans for solar system exploration. One short-term highlight is the NASA mission Juno which will arrive at Jupiter in summer 2016 and have just a year to learn as much as it can about the jovian system before its spacecraft components are fried by Jupiter's intense radiation. Other longer-term ambitions centre around the ice giants, Uranus and Neptune, which challenge our understanding of how the Sun influences planetary systems.
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| Probing emitter-cavity dressed states through environmental transitions |
| Dr Ahsan Nazir |
University of Manchester |
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14:30, Friday 6 February 2015 | | Physics Seminar Room (Building 46/5081) |
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In this talk, Dr Nazir will show that emitter-cavity dressed states may be probed through interactions with a thermal environment in solid-state cavity QED systems. This is true even in regimes that can be described semiclassically in the absence of such an environment, for example when the emitter-cavity coupling strength is dominated by cavity losses. This behaviour thus heralds a failure of the semiclassical approach, and challenges the notion that coupling to a thermal bath supports a more classical description of the system.
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| The Development of Optical Lattice Clocks |
| Dr Liz Bridge |
Durham University |
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14:30, Friday 9 January 2015 | | Physics Seminar Room (Building 46/5081) |
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Optical lattice clocks demonstrate world-leading fractional frequency uncertainty and instability. Recent publications state a fractional frequency uncertainty of 2 x 10-18 (equivalent to losing one second in 160 billion years), which is 50 times better than the caesium fountains currently used to define the unit of time. This level of certainty and stability allows us to look for temporal variations in the fundamental constants, such as the fine structure constant and the electron-proton mass ratio, and could lead to a wide range of technological advances. In this talk, Dr Bridge provide an overview of the recent progress of atomic frequency metrology, highlighting key considerations, and discuss the possible future developments, including using Rydberg spin squeezing to further reduce the instability.
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| Imaging at the Speed of Light |
| Prof Jonathan Leach |
Heriot-Watt University |
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14:30, Friday 12 December 2014 | | Physics Seminar Room (Building 46/5081) |
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How do you take images so fast that you can see light travelling through air? And how do you use the latest technology to look around corners and see objects hidden from view? Prof Leach will talk about our recent research using a very specialised camera with some very important features. The first is its sensitivity to single photons – each pixel is around ten times more sensitive than a human eye; the second is its speed – each pixel can be activated for just 67 picoseconds, that's more than a billion times faster than we can blink. The camera allows us to film at the speed of light – we can video pulses of light as they travel through air.
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| Controlling Light at the Quantum Level: on-demand single-photon sources on a chip |
| Dr Luca Sapienza |
University of Southampton |
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14:30, Friday 28 November 2014 | | Physics Seminar Room (Building 46/5081) |
The field of photonics has seen a tremendous development in recent years. The "photonic revolution", based on the use of light as the information carrier, is expected to have an impact on everyday life, providing faster and secure communication, as well as more efficient computation schemes.
Thanks to fundamental research and technological advances, we can now generate, trap, guide and detect light at its most fundamental level, the single photon.
Dr Sapienza will give an introduction to solid-state single-photon sources and present his group's recent results on single quantum dot emitters integrated in optical cavities, on a semiconductor chip.
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| The Shapes of Supernovae |
| Dr Justyn Maund |
University of Sheffield |
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14:30, Friday 21 November 2014 | | Physics Seminar Room (Building 46/5081) |
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Supernovae are the violent explosions that mark the deaths of certain types of stars. The complex shapes observed for a handful of centuries-old, nearby supernovae hint at the complicated physics involved in the explosion mechanism itself. Dr Maund will provide an overview of how astronomers have attempted to observe the shapes of supernovae, and show how the technique of spectropolarimetry is our best hope for working out how some stars actually explode.
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| Microscopic Mapping of III-Nitride Blue LEDs and Nanostructures |
| Prof Rob Martin |
University of Strathclyde |
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14:30, Friday 14 November 2014 | | Physics Seminar Room (Building 46/5081) |
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Quantum wells of Indium Gallium Nitride lie at the heart of the extremely efficient blue and white LEDs that are having a major impact in lighting and other commercially important areas. Prof Martin will describe work to investigate sub-micron spatial variations in these devices: both (1) naturally occurring inhomogeneities that might be expected to severely limit device performance to levels well below those currently achieved and (2) deliberately engineered nanostructures designed to improve performance (such as arrays of nanorods or core-shell LEDs).
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| Superabsorption of Light via Quantum Engineering |
| Dr Erik Gauger |
University of Oxford |
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14:30, Friday 7 November 2014 | | Physics Seminar Room (Building 46/5081) |
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Sixty years ago Robert Dicke introduced the term superradiance to describe a signature quantum effect: N atoms can collectively emit light at a rate proportional to N2. Structures that superradiate must also have enhanced absorption, but the former always dominates in natural systems. In this talk, Dr Gauger will show that modern quantum control techniques can overcome this restriction in certain simple nanostructures. The protocol for superabsorption is an instance of quantum engineering inspired by the design of naturally occurring biological systems, and opens the prospect of a new class of quantum nanotechnology with potential applications including photon detection and light harvesting.
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| The Large Synoptic Survey Telescope |
| Prof Ian Shipsey |
University of Oxford |
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14:30, Friday 31 October 2014 | | Physics Seminar Room (Building 46/5081) |
Technological advances have made possible the deep optical survey of a large fraction of the visible sky, enabling the search for small moving objects in the solar system, studies of the assembly history of the Milky Way, the exploration of transient sky, and the establishment of tight constraints on models of dark energy. With an 8.4 m primary mirror, and a 3.2 Gigapixel, 10 deg2 CCD camera, LSST will provide nearly an order of magnitude improvement in survey speed, and is expected in its first month of operation to survey more of the optical universe than all previous telescopes built by mankind.
In ten years, the LSST will survey half of the sky in six optical colors down to 27th magnitude, revealing four billion new galaxies and 10 million supernovae. LSST will produce 15 terabytes of data per night, processed by dedicated computing facilities in near real time. Prof Shipsey will discuss some of the science that will be made possible by the construction of LSST, especially dark energy science, which constitutes a profound challenge to particle physics and cosmology, and give an overview of the technical design and current status of the project.
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| On The Correspondence Principle and Quantum Measurement |
| Prof Mark Everitt |
University of Loughborough |
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14:30, Friday 17 October 2014 | | Physics Seminar Room (Building 46/5081) |
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Prof Everitt will overview the quantum to classical transition for a number of systems including a simple three body problem, a two level atom coupled to a field. By considering a dissipative quantum mechanical model of the projective measurement of a qubit, he will discuss whether such an approach does really make a good model of the measurement process and if all the "axioms" of quantum theory are really needed.
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| Neutrinos on Ice: using IceCube to chase a ghost particle |
| Prof Jason Koskinen |
Niels Bohr Institute, University of Copenhagen |
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14:30, Friday 10 October 2014 | | Physics Seminar Room (Building 46/5081) |
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The IceCube neutrino observatory is a cubic kilometer of instrument ice situated at the South Pole. With sensitivity to neutrinos over an energy range of 10 GeV to 10 PeV, it is a unique instrument to study both astrophysics and fundamental particle physics. Prof Koskinen will cover the most recent results from high-energy astrophysical neutrino detection, neutrino oscillation, and prospects for next generation upgrades.
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| Quantum Photonics with Optical Nanofibres |
| Prof Kohzo Hakuta |
University of Electro-Communications, Chofu |
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14:30, Friday 3 October 2014 | | Physics Seminar Room (Building 46/5081) |
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Prof Hakuta will discuss quantum photonics with optical nanofibres that may open a new route to manipulate single atoms and single photons. The key idea of the method is to use sub-wavelength diameter silica fibres, termed optical nanofibres, for strongly confining the photon-mode density around the nanofibre. First, he will discuss theoretically how various freedoms of atoms and photons can be manipulated with optical nanofibres, and the experimental demonstration of how such freedoms have been manipulated with optical nanofibres. Examples include single atom spectroscopy and efficient channeling of fluorescence photons into the guided modes. Regarding the channeling, Prof Hakuta's group has shown experimentally that, by placing one "atom" on nanofibre surface, the fluorescence photons are channeled into the guided modes with efficiency higher than 20%. Furthermore, he will show theoretically that the channeling efficiency can be enhanced to 90% or higher, by fabricating cavity structure on nanofibres. Recent progress on experimental realization of nanofibre-cavity system will be discussed. Prof Hakuta will discuss also the realization of the cavity QED conditions in the Purcell regime using the nanofibre-cavity system, and report the observation of significant enhancement of the spontaneous emission rate into the nanofibre guided modes for single quantum dots. Future prospects are also discussed.
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| The Rosetta Mission: the story so far |
| Dr Matt Taylor |
European Space Agency |
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14:30, Friday 23 May 2014 | | Physics Seminar Room (Building 46/5081) |
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The Rosetta Mission is the third cornerstone mission of the ESA programme Horizon 2000. The aim of the mission is to map the comet 67-P/Churyumov-Gerasimenko by remote sensing, to examine its environment insitu and its evolution in the inner solar system. The lander Philae will be the first device to land on a comet and perform in-situ science on the surface. Launched in March 2004 and after a number of gravity assists and various asteroid fly –bys, the spacecraft entered deep space hibernation in June 2011. Nearly 10 years after launch on 20th January 2014 at 10:00 UTC the spacecraft woke up from hibernation to get ready for comet rendez-vous. This presentation will provide a brief overview of the mission up to date and provide an insight into the exciting years we have ahead of us as Rosetta reaches and studies its target.
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| Modelling Complex Self Assembly: the bad news is the good news |
| Prof Daan Frenkel |
University of Cambridge |
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14:30, Friday 16 May 2014 | | Physics Seminar Room (Building 46/5081) |
A holy grail of nano-technology is to create truly complex, multi-component structures by self assembly. In this talk, Prof Frenkel will discuss some of the most important parameters that can be used to control self-assembly: packing entropy and molecular recognition. Both the role of packing entropy and that of molecular recognition are counter-intuitive.
Prof Frenkel will discuss the unexpected role of entropy as an ordering force, and will show that in molecular recognition, less is more.
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| Surfaces: Topographical Dynamics and Preferential Adsorption |
| Prof Dirk Broer |
Eindhoven University of Technology |
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14:30, Friday 28 March 2014 | | Physics Seminar Room (Building 46/5081) |
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Liquid crystal polymer networks can be made responsive to triggers as light, temperature, moisture, pH and specific gases and chemicals. The response may manifest itself as changes in appearance such as color or transmission of light, and/or in shape when deforming from a flat film to a preset complex geometry. This presentation will focus on triggered changes in the surface topography. By manipulating local molecular order we are able to switch a surface from flat to corrugated. Protrusions may form randomly, comparable to fingerprints, or at preset locations. When formed they change surface properties like friction and wetting. By using a similar technology, films can be made with a large internal surface area in the form of nanopores. These nanopores can selectively adsorb species depending on charge or size. The polarity of the pores can be switched by light which changes the uptake of materials.
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| Tuning In the Radio Sun |
| Prof Peter Gallagher |
Trinity College, Dublin |
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14:30, Friday 21 March 2014 | | Physics Seminar Room (Building 46/5081) |
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Cosmic rays and solar energetic particles may be accelerated to relativistic energies by shock waves in astrophysical plasmas. On the Sun, shocks and particle acceleration are often associated with the eruption of magnetized plasmoids, called coronal mass ejections (CMEs). However, the physical relationship between CMEs and shock particle acceleration is not well understood. In this talk, Prof Gallagher will show how extreme ultraviolet, radio and white-light images can be used to study CME-induced shocks and associated phenomena such as large-scale coronal waves. He will also show how LOFAR is giving a new insight into our understanding of electron acceleration in the solar corona.
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| Laser-cooled molecules and their applications |
| Dr Mike Tarbutt |
Imperial College, London |
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14:30, Friday 14 March 2014 | | Physics Seminar Room (Building 46/5081) |
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Cold molecules are useful for many applications, from precision measurement to quantum simulation. Dr Tarbutt will first present a measurement that uses cold CH molecules to test the idea that the fundamental constants may differ between the high and low density environments of the Earth and the interstellar medium, as hypothesized in some theories of dark energy. Then he will show how laser cooling can be applied to some molecules, and present recent results from the Imperial College group on laser cooling of CaF.
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| Nanoparticles for Imaging: from quantum dots, to polymers, to works |
| Dr Mark Green |
King's College, London |
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14:30, Friday 28 February 2014 | | Physics Seminar Room (Building 46/5081) |
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The use of nanoparticles in imaging applications has become a mainstream discipline. Since the seminal use of quantum dots in simple imaging in 1997, the area has been the focus of a massive amount of research, despite the fact that these solid state materials have obvious down falls – notably the toxicity associated with metals such as cadmium. The benefits, such as enhanced stability and tuneable, multicolour, narrow emission are desirable and in some cases outweigh the negative aspects. In this talk, Dr Green will describe the work undertaken in the last several years at KCL in the preparation of quantum dots, alternatives such as metal-free particles, and explain the more unusual results such as the biosynthesis of quantum dots inside living animals.
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| Nature's Ears: ideal models for engineered acoustic systems? |
| Dr James Windmill |
University of Strathclyde |
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14:30, Friday 21 February 2014 | | Physics Seminar Room (Building 46/5081) |
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Humanity uses sound frequencies across a far greater range than we can hear for numerous extremely beneficial tasks. In Nature a huge variety of animals have evolved ears, many of which are sensitive to sounds beyond human audibility. An obvious example is the bat, where different species have evolved extremely precise ultrasonic echolocation techniques to detect insects in flight to catch and eat. Equally, an enormous variety of insects have evolved miniature ears to detect sound in order to communicate or to avoid predators like the bat. Over past decades engineers have looked at the use of sound by these creatures, seeking inspiration to solve acoustic problems. This talk will briefly look at examples of the unexpected characteristics found in insect hearing systems, and discuss work on bio-inspired acoustic systems.
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| Fabricating Optical Integrated Devices for Quantum Computation |
| Dr James Gates |
University of Southampton |
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14:30, Friday 14 February 2014 | | Physics Seminar Room (Building 46/5081) |
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Dr Gates will present his group's work on single photon quantum circuits, sources and detectors from the past 7 years. Over this time Southampton has been one of the world's leading fabricators of optical integrated quantum devices. James will give an overview of devices and results with particular emphasis on the challenges of photonic engineering of quantum devices. Much of the work is part of a continuing collaboration with NIST and the University of Oxford and he will also discuss the future methodology and devices currently being developed.
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| SMART-1: Europe's First Mission to the Moon |
| Dr Barry Kellett |
Rutherford Appleton Laboratory |
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14:30, Friday 7 February 2014 | | Physics Seminar Room (Building 46/5081) |
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SMART-1 was ESA's first technology demonstration mission... a small mission to test various components and technologies that ESA thought it needed for the future. For example, SMART-1 was the first ESA mission to fly Lithium batteries! However, the main technology under test was the solar electric Ion Drive. This helped SMART-1 set two new world records: the SLOWEST mission to ever reach the Moon (over 15 months!) and, second, the most fuel efficient mission to the Moon – just 80 kg of fuel used! Dr Kellett will also briefly mention Chandrayaan-1 – the 1st Indian mission to the Moon!
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| iSense: A Cold Atom Quantum Technology Platform |
| Prof Kai Bongs |
University of Birmingham |
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14:30, Friday 31 January 2014 | | Physics Seminar Room (Building 46/5081) |
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The iSense project brings together leading European atom interferometry groups in order to overcome the technological bottleneck in cold atom quantum technology. The field of cold atoms and precision measurements with atoms has seen 4 Nobel prizes in the last twenty years and is hosting vibrant research by 1000s of groups worldwide. However, despite groundbreaking results in quantum simulation, promising advances in quantum computing and quantum communication as well as quantum sensors surpassing the best classical devices, this field is still largely confined to the research laboratory. The reason lies in the complex and delicate laser, vacuum and electronic systems needed to create the cold atom quantum resource needed for all these applications. iSense aims at a significant shrinkage and robustness increase of the underlying technologies and to demonstrate the concept in a potable atom interferometer gravity sensor. This talk will discuss the technology and science approaches in iSense and present the current status of the project with an outlook into cold atom quantum technologies.
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| Mission Applications and Engineering Challenges for Solar Sail Spacecraft |
| Prof Colin McInnes |
University of Strathclyde |
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14:30, Friday 13 December 2013 | | Physics Seminar Room (Building 46/5081) |
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Solar sailing is a novel means of spacecraft propulsion which uses a large, deployable reflective film to provide a small, continuous thrust from the action of solar radiation pressure. This talk will discuss a range of mission applications for solar sail spacecraft and identify the key engineering challenges involved. In addition, the properties of families of highly non-Keplerian orbits will be discussed, along with their potential applications for future space weather and Earth observation missions. A forthcoming solar sail demonstration mission will be also be discussed.
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| Exploring the Diversity of Exoplanets |
| Dr Suzanne Aigrain |
University of Oxford |
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14:30, Friday 6 December 2013 | | Physics Seminar Room (Building 46/5081) |
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Planets orbiting other stars than the Sun were first discovered only 20 years ago, but since then their study has become one of the most active and fertile fields in astronomy. With dedicated telescopes scanning the skies continuously, we are now discovering hundreds of new systems every year, many of which are utterly unlike our own. We can also study study the atmospheres of some of these distant worlds in astonishing detail. Dr Aigrain will take us on a brief tour of recent exoplanet detection and characterisation highlights, and finish with a preview of how we might search for signs of life on another world.
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Dynamics and Control of Bird and Insect Flight
and its applications to unmanned air systems |
| Prof Graham Taylor |
University of Oxford |
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14:30, Friday 29 November 2013 | | Physics Seminar Room (Building 46/5081) |
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The dynamics of flapping flight differ fundamentally from those of fixed- or rotary-wing aircraft. This seminar will give a flavour of the Oxford research on the guidance, dynamics, and control of bird and insect flight. This research aims to uncover the fundamental organizational principles underpinning the design of naturally evolved control systems, and to apply this insight to the design of unmanned air systems. The talk will probe a few key examples, including the relationship between physics and physiology in hawkmoths, the mechanics of the insect flight motor as revealed by time-resolved X-ray tomography, and the visually-guided attack strategies of peregrine falcons.
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Acoustics of a Changing World
whales, icebergs, seismics and marine renewables |
| Dr Philippe Blondel |
University of Bath |
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14:30, Friday 15 November 2013 | | Physics Seminar Room (Building 46/5081) |
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Oceans cover most of the Earth. The last decades have seen a host of wonderful discoveries, most of them using sound and sonars. This talk will present examples from around the world, taken from the presenter's own research. The first part of the talk will present the innovative sensors (many of UK design) which have revolutionised our knowledge of the "Blue Planet" and its seabeds, from mid-ocean ridges to coastal areas. The second part will focus on applications, including coastal habitats, Marine Renewable Energies and the migrations of grey whales, as well as the role of acoustic sensors in monitoring the effects of climate change and human activities as far as the Arctic.
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Optically Pumped Semiconductor Disk Lasers:
design, growth, characterization and potential applications |
| Alexander Hein |
University of Ulm |
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14:30, Friday 1 November 2013 | | Physics Seminar Room (Building 46/5081) |
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Optically Pumped Semiconductor Disk Lasers (OPSDLs) combine the unique features of high output power, excellent beam quality, and wide wavelength coverage. In the fundamental regime, the wavelengths of these sources can be continuously addressed from 0.6 μm to well beyond 2.5 μm by choosing an appropriate material system. The spectral band is essentially increased by generation of higher harmonics, thus, the shorter visible spectrum as well as the ultra-violet can be accessed. Due to this lack of wavelength discontinuity these lasers enable a variety of new applications in spectroscopy, forensics, and many other fields.
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| Photonic Quantum Technologies |
| Prof Jeremy O'Brien |
University of Bristol |
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14:30, Friday 25 October 2013 | | Physics Seminar Room (Building 46/5081) |
Quantum information science aims to harness uniquely quantum mechanical properties to enhance measurement, information and communication technologies, as well as to explore fundamental aspects of quantum physics. Photons are particularly appealing for their low-noise properties and ease of manipulation at the single qubit level, as well as for quantum communication, metrology and measurement.
The Bristol group has developed an integrated waveguide approach to photonic quantum circuits for high performance, miniaturization and scalability, and has begun to address the challenges of scaling up quantum circuits using new insights into how controlled operations can be efficiently realised. They have shown how quantum circuits can be reconfigured, using thermo-optic phase shifters to realise a highly reconfigurable quantum circuit able to perform almost any function on two photonic qubits, and electro-optic phase shifters to rapidly manipulate the path and polarisation of telecom wavelength single photons. They have addressed miniaturisation using multimode interference coupler architectures to directly implement Hadamard operations and the 'Boson sampling problem', and by using high refractive index contrast materials in which they have implemented quantum walks of correlated photons and demonstrated generation of orbital angular momentum states of light. They have incorporated microfluidic channels for the delivery of samples to measure the concentration of a blood protein with entangled states of light, and have begun to address the integration of superconducting single photon detectors and non-linear single photon sources. Finally, Prof O'Brien will review recent work on fundamental aspects of quantum measurement, including a quantum version of Wheeler's delayed choice experiment.
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| Optical Fibres for Astrophotonics |
| Prof Tim Birks |
University of Bath |
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14:30, Friday 18 October 2013 | | Physics Seminar Room (Building 46/5081) |
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Astrophotonics is the application of photonics technology to solve problems in observational astronomy. In this talk, Prof Birks will describe how optical fibres are being developed to filter out unwanted IR emissions from the Earth's atmosphere, which hampers ground-based observations of the early Universe.
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| Animal Navigation using Magnetically Sensitive Spins |
| Prof Peter Hore |
University of Oxford |
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14:30, Friday 11 October 2013 | | Physics Seminar Room (Building 46/5081) |
Migratory birds travel spectacular distances each year, navigating and orienting by a variety of means, most of which are poorly understood. Among them is a remarkable ability to perceive the intensity and direction of the Earth's magnetic field. Biologically credible mechanisms for the sensing of such weak fields (25-65 microtesla) are scarce and in recent years just two proposals have emerged as frontrunners. One, essentially classical, centres on iron-containing particles. The other relies on the magnetic sensitivity of short-lived radical pairs formed by photoinduced electron transfer. This model began to attract interest following the proposal that the necessary photochemistry could take place in the bird's retina in specialised photoactive proteins called cryptochromes. The coherent dynamics of electron-nuclear spin states of pairs of radicals is conjectured to lead to changes in the yields of reaction products even though the Zeeman interaction with the geomagnetic field is more than six orders of magnitude smaller than kT.
In this seminar, Prof Hore will outline some of the experimental evidence for the cryptochrome hypothesis, discuss the interpretation of the reported effects of weak (nanotesla) radiofrequency fields on the magnetic orientation of European robins, and comment on the extent to which cryptochromes are fit-for-purpose as magnetoreceptors.
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| DEAP/CLEAN-ing Dark Matter: the search for direct detection with liquid Argon |
| Prof Jocelyn Monroe |
Royal Holloway, University of London |
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14:30, Friday 4 October 2013 | | Physics Seminar Room (Building 46/5081) |
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The nature of dark matter is one of the fundamental questions in physics today. A world-wide race is on to directly observe dark matter particles interacting in terrestrial detectors. A number of experiments have recently claimed to detect dark matter interactions, via both direct and indirect experimental methods, although none are yet independently confirmed. The DEAP/CLEAN collaboration is developing a novel approach to dark matter detection, using very large Liquid Argon detectors instrumented with photomultiplier tubes to observe scintillation light from dark matter scatters in the detector. This design strategy emphasizes scalability to target masses of order 100 tons. This talk will discuss dark matter detection, review recent results from around the world, and describe the experimental technique and status of the DEAP/CLEAN experiment.
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| Terahertz Spectroscopy of Nanomaterials |
| Dr Michael Johnston |
University of Oxford |
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14:30, Friday 14 June 2013 | | Physics Seminar Room (Building 46/5081) |
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Optical-pump terahertz probe spectroscopy is an ideal technique for studying the electronics properties of nanomaterials. In this talk, Dr Johnston will introduce this non-contact method of characterising materials, before presenting recent terahertz conductivity measurements on semiconductor nanowires, graphene and metal oxides. The large surface area to volume ratio of these nanomaterials can be used to tailor their electronic properties for future device applications.
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| Gamma-Ray Bursts: the most energetic cosmic explosions since the Big Bang |
| Prof Ed van den Heuvel |
University of Amsterdam |
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14:30, Friday 7 June 2013 | | Physics Seminar Room (Building 46/5081) |
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Gamma-ray bursts were discovered with American spy satellites in 1967, but their nature and origin remained a mystery for 30 years. In 1997, thanks to a small Italian-Dutch satellite, it was discovered that they originate at large cosmological distances and result from extremely powerful cosmic explosions, marking the death events of very massive stars. Probably they are the birth events of stellar-mass black holes, although also other explanations remain possible.
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| Solid-State Quantum Optics |
| Prof Mark Fox |
University of Sheffield |
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14:30, Friday 31 May 2013 | | Physics Seminar Room (Building 46/5081) |
Quantum optics describes the interaction between light and matter at the quantum level. The subject developed primarily from atomic physics, but in recent years the scope has expanded widely to include many solid-state systems as well. This has occurred to such an extent that some of the best examples of quantum-optical effects are now observed in the solid state.
Semiconductor quantum dots provide an excellent system for exploring solid-state quantum-optical phenomena on account of their large optical dipole moment and easy incorporation into advanced photonic devices. In this colloquium, Prof Fox will illustrate some of the quantum-optical phenomena that can be observed from quantum dots, and then explain how these effects can be enhanced by coupling the dots to high quality-factor resonant cavities.
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| Electro-Optic Sensing for Defence and Security |
| Dr Richard Hollins |
Dstl, Porton Down |
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14:30, Friday 24 May 2013 | | Physics Seminar Room (Building 46/5081) |
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The seminar will show how Dstl investigates and exploit new electro-optic sensing to meet the ever-changing needs of defence and security. Activity in a variety of fields including counter-terrorism, optical communications, and sensor protection will be described. The talk will try to illustrate how Dstl conceives and investigates solutions to defence and security challenges by harnessing new technologies emerging from industry and academia.
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| Interferometry with Bose-Einstein Condensates |
| Prof Erling Riis |
University of Strathclyde |
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14:30, Friday 17 May 2013 | | Physics Seminar Room (Building 46/5081) |
Progress is reviewed on experiments studying the interference of Bose-Einstein condensates (BECs). Using an optical barrier in an elongated magnetic trap we have obtained clear interference fringes for condensates separated by macroscopic distances.
Current work includes the development of an inductively coupled ring trap intended for Sagnac interferometry. This trap configuration has the potential for being scaled to a size compatible with integration in chip-scale interferometers. Recent progress will also be detailed on the development of planar diffractive optical elements for the generation of the beams required for a magneto-optic trap with a view to realise simple chip-based sources of ultra-cold atoms.
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Nearly 100 Years after General Relativity: was Einstein right?
an answer by a radio astronomer |
| Prof Michael Kramer |
Max-Planck-Institute for Radio Astronomy |
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14:30, Friday 3 May 2013 | | Physics Seminar Room (Building 46/5081) |
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Nearly 100 years ago Einstein proposed a radical change in the understanding of gravity. Since then his theory of general relativity (GR) withstood all tests. Today, we see apparent phenomena that may be explainable by deviations from GR, and hence the question whether Einstein was right, is as topical as ever. This talk will present the some of the latest and best tests of theories of gravity using radio pulsars.
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| Mechanical Atom Manipulation: towards a matter compiler? |
| Prof Philip Moriarty |
University of Nottingham |
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14:30, Friday 26 April 2013 | | Physics Seminar Room (Building 46/5081) |
Can we design and construct a matter compiler? That is, is it possible to conceive of a scheme whereby the fundamental atomic/molecular building blocks of matter can be autonomously and intelligently manipulated via software to form a nanoscopic, microscopic, or even macroscopic product? This is the essence of the highly controversial "molecular manufacturing" concept put forward by K. Eric Drexler in the eighties (and which was originally inspired by Feynman's musings on the ultimate limits of miniaturisation in 1959).
In this talk, Prof Moriarty will first reappraise Drexler's matter compilation scheme in the context of the latest developments in (sub)atomic resolution scanning probe microscopy (SPM) before describing some of his recent work in three areas of key relevance to the matter compilation concept:
• Atom switching and manipulation driven purely by the making and breaking of a single chemical bond;
• Probe engineering – tuning the atomic structure of a scanning probe microscope tip by controlled pick-up and reorientation of a C60 molecule;
• Automated probe microscopy via evolutionary optimization at the atomic scale.
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| Pulsed Laser-Assisted Generation of Novel Materials and Related Applications |
| Dr Emmanuel Stratakis |
University of Crete |
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14:30, Friday 15 March 2013 | | Physics Seminar Room (Building 46/5081) |
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This talk will review recent work on the application of pulsed laser processing for novel materials production. Two distinct approaches are reviewed including laser materials modification in controlled gas and liquid media respectively. In particular, it is shown that the artificial surfaces obtained by femtosecond laser texturing of solid surfaces in reactive gas atmosphere exhibit roughness at both micro- and nano-scales that mimics the hierarchical morphology of natural surfaces. Depending on the functional coating deposited on the laser patterned three dimensional structures, artificial surfaces that may be achieved are: (a) of extremely low surface energy, thus water repellent and self-cleaned; (b) responsive, i.e., show the ability to change their surface energy in response to different external stimuli such as light, electric field and pH. The behaviour of different kinds of cells cultured on laser engineered substrates of various morphologies was investigated. The second part of the talk will be focused on the pulsed laser assisted synthesis and functionalization of new types of nanomaterials for organic electronics. Results on the formation of plasmonic nanoparticles, using pulsed laser ablation in liquid media will be presented. Furthermore, rapid and facile methodologies for the photochemical reduction, doping and functionalization of graphene oxide (GO) sheets, based on pulsed UV laser processing of GO, will be demonstrated. Potential applications of laser synthesized and modified materials in organic electronics, particular to bulk heterojunction organic solar cells are demonstrated and discussed.
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| Pre-Cooled Airbreathing Engines: a new generation of high-speed propulsion |
| Mr Alan Bond |
Reaction Engines Ltd |
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14:30, Friday 8 March 2013 | | Physics Seminar Room (Building 46/5081) |
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Liquid hydrogen is an excellent coolant with a very high heat capacity. It has proved possible to design airbreathing engines using this fuel to reach Mach 5 within the limitations of currently available materials and engineering technology. In combination with other engine types, eg rocket or fan, a whole range of propulsion options are possible which will shrink the world to less than 5 hours to anywhere and enable an aircraft to fly into space to do a job and then return to repeat it again within a few hours.
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| Molecules and Electrons Illuminate Complex Nanophotonics Structures |
| Dr Riccardo Sapienza |
King's College, London |
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14:30, Friday 1 March 2013 | | Physics Seminar Room (Building 46/5081) |
Numerous optical technologies and quantum optical devices rely on the controlled coupling of a local emitter to its photonic environment, which is governed by the local density of optical states (LDOS). Light spontaneous emission, absorption and scattering are all related to the LDOS which can be engineered in dielectric and metallic nano structures. Dr Sapienza will present how a nano-sized light probe can illuminate complex materials and shed light on their optical properties and modes.
This talk will also report nanoscale mapping of the local density of states by cathodo-luminescence microscopy, a combination of electron-beam scanning and optical spectroscopy that relies on scanning a transient dipolar emitter induced by electron beam bombardment with respect to its photonic environment while measuring the total emitted power. Each individual electron traversing the photonic structure generates a nanoscale transient dipole by the accelerated charge which we exploit as a local probe of the LDOS. With unprecedented resolution (~10 nm), localized photonic crystal cavity modes are imaged in a nano-structured silicon nitride membrane, over the visible spectrum into the near-IR, and individual cavity modes are identified that are spatially different and we map their LDOS. Measurements also reveal extended Bloch modes that are delocalized over the crystal and periodically modulated. Moreover, by momentum spectroscopy, angular emission pattern of the radiation emitted, which exhibits complex diffraction patterns, is resolved.
Dr Sapienza will also discuss recent studies of fluorescence from a nano-sized emitter embedded in complex photonic media, such as photonic crystals and random powders, using fluorescence dynamics to measure LDOS distributions in 3D disordered dielectric powders and observing a surprisingly long-tailed distribution of the LDOS with Purcell factor up to ~10. He will discuss how these experimental results fed the ongoing discussion on the dependence of the C0 correlation function on macroscopic disorder parameters.
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| The Journey in the Search for the Higgs Boson in CMS at the LHC |
| Prof Tejinder (Jim) Virdee |
CERN & Imperial College, London |
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14:30, Friday 8 February 2013 | | Physics Seminar Room (Building 46/5081) |
The LHC accelerator has collided protons and lead ions at unprecedented high energies. It has delivered an integrated luminosity of ~5 pb-1 at √s=7 TeV and ~20 fb-1 at √s=8 TeV to the general-purpose experiments ATLAS and CMS.
In July 2012, both experiments reported the discovery of a new Higgs-like boson.
This talk will outline some of the challenges faced during the construction of the CMS experiment, its operation and performance, and selected physics results. In particular recent results relating to the Higgs-like boson will be discussed as well as the outlook.
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| Cold Ion Crystals for Quantum Computing and Quantum Simulation |
| Prof Ferdinand Schmidt-Kaler |
University of Mainz |
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14:30, Friday 18 January 2013 | | Physics Seminar Room (Building 46/5081) |
Long-lived states in trapped ions are well suited for implementing quantum information processes, by generating entangled states in linear ion crystals. All the essential building blocks of quantum interactions have been demonstrated, but future challenges need multiple ionic quantum bits in versatile geometric configurations. Prof Schmidt-Kaler will describe how the state-of-the-art may be extended by combining ion entanglement operations with rapid changes of the ion positions for fast transport and modifications of ion configurations in two-dimensional crystal arrays.
For a scalable quantum computer, Prof Schmidt-Kaler's group is following an approach proposed by Nobel laureate Dave Wineland, whereby ions are transported in a multi-segmented trapping device. To optimize the scheme, ultra-fast ion transport has been achieved without motional excitation at the destination, allowing non-classical quantum states of motion to be generated.
A second important application of trapped ions is quantum simulation, and Prof Schmidt-Kaler will outline the formation and precise investigation of planar zig-zag ion crystals, in which the traversal of a symmetry-breaking phase transition can lead to separated regions with incompatible symmetries and the formation of defects at their boundaries. Such defect formation follows universal scaling laws prescribed by the Kibble-Zurek mechanism, which are observed in the clean model system of trapped ions. Ions in planar crystals may be employed also for simulating spin-spin interactions in frustrated geometries, highly relevant for the observation of unexplored quantum phases and transitions.
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Carbon Geostorage - the Monitoring Challenge:
inflation, muons and the Moon |
| Prof Jon Gluyas |
Durham University |
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14:30, Friday 11 January 2013 | | Physics Seminar Room (Building 46/5081) |
Fossil fuel consumption puts around 7 bn tonnes of CO2 into the atmosphere each year, and the CO2 concentration has risen substantially since the industrial revolution. While humankind is unlikely to stem its dependence in the near term, we can dramatically reduce emissions of this greenhouse gas using carbon capture and storage. The first programmes have begun, and legislation and common sense require that the process be monitored. While many tools already exist in the petroleum industry, new, low cost, passive, continuous monitoring techniques are required.
Prof Gluyas will examine two technologies to monitor both the injection and storage of CO2. Satellite-measured changes in surface elevation have allowed the measurement of CO2 injection beneath the bare Algerian desert, but present difficulties in areas of agriculture and vegetation; some early results will be presented. Muon tomography is a theoretically feasible alternative, and is undergoing its first practical test in the deep Boulby Potash Mine in northern England - an ideal location for testing the ultimate sensitivity, which might reveal the diurnal and monthly tidal cycles using muon detectors deep within the mine. The first few carbon storage programmes have begun with dense phase CO2 being injected deep into porous and permeable sites; comparable to the natural traps in which oil and gas occur. Legislation as well as good, common sense dictates that the carbon dioxide once injected needs to be monitored – possibly for generations. Many of the tools used to find and monitor production of petroleum can be used to monitor carbon storage sites but a combination of the timeframes involved and the fact that storage of CO2 does not intrinsically create value (it is waste disposal) mean that a suite of new, low cost, passive, continuous monitoring technologies are require.
Here Prof Gluyas will examine two technologies which have the potential to help monitor both injection and storage of CO2 continuously and at a cost lower than the conventional methods used by the petroleum industry. These have hitherto have not been used by the emerging CCS industry.
InSAR satellite technology has been used to measure changes in elevation, surface inflation, associated with injection of CO2 into the deep subsurface at In Salah in the bare desert of Algeria but how do you apply it to onshore areas that are not bare deserts but rural areas in which a ploughed field or annual vegetation growth could mask changes in elevation of underlying bedrock? Prof Gluyas will present some early results.
The theoretical feasibility of using muon tomography for continuous monitoring of injection of supercritical carbon dioxide into deep geological storage for carbon storage as a climate change mitigation technology has been proven already. Although theoretically feasible it is essential to take the next step and prove its practical feasibility. As a first practical test of feasibility we are using the deep Boulby Potash Mine in northern England provides us with a unique environment in which to measure muon fluxes, develop and deploy instrumentation and test the sensitivity of our method. The mine extends offshore and provides the ideal location for the ultimate sensitivity test. Might it be possible to detect the diurnal and monthly tidal cycles from deep within the mine using muon detectors?
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| Astronomy by Microscope |
| Prof Monica Grady |
Open University |
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14:30, Friday 7 December 2012 | | Physics Seminar Room (Building 46/5081) |
Traditionally, astronomers study stars and planets by telescope. But we can also learn about them by using a microscope – through studying meteorites. From meteorites, we can learn about the processes and materials that shaped the Solar System and our planet. Tiny grains within meteorites have come from other stars, giving information about the stellar neighbourhood in which the Sun was born.
Meteorites are fragments of ancient material, natural objects that survive their fall to Earth from space. Some are metallic, but most are made of stone. They are the oldest objects that we have for study. Almost all meteorites are fragments from asteroids, and were formed at the birth of the Solar System, approximately 4570 million years ago. They show a compositional variation that spans a whole range of planetary materials, from completely unmelted and unfractionated stony chondrites to highly fractionated and differentiated iron meteorites. Meteorites, and components within them, carry records of all stages of Solar System history. There are also meteorites from the Moon and from Mars that give us insights to how these bodies have formed and evolved.
In her lecture, Prof Grady will describe how the microscope is another tool that can be employed to trace stellar and planetary processes.
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| Exploring the Quantum Superposition Principle with Macromolecules and Molecular Clusters |
| Prof Markus Arndt |
University of Vienna |
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14:30, Friday 30 November 2012 | | Physics Seminar Room (Building 46/5081) |
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Quantum delocalization and quantum interference with massive matter have puzzled physicists for decades since these phenomena question our common understanding of reality, locality or space-time. Recent experimental advances have allowed us to devise new molecular sources, interferometer arrangements and detection methods that open the path to testing quantum mechanics at the interface to philosophy. At the same time modern particle interferometers generate a flying molecular nanostructure which acts as a fine rule for sensitive force measurements with applications in physical chemistry.
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| Cloudspotting and Wave-Watching |
| Mr Gavin Pretor-Pinney |
author; founder of the Cloud Appreciation Society |
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14:30, Friday 23 November 2012 | | Physics Seminar Room (Building 46/5081) |
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Gavin Pretor-Pinney, founder of The Cloud Appreciation Society, is the author of the bestselling Cloudspotter's Guide and Cloud Collector's Handbook. More recently, he wrote The Wavewatcher's Companion, which won the 2011 Royal Society Winton Prize for Science Books. In it, he reminded us that ocean waves, so familiar to us all, are just a tiny proportion of the many waves that surround us, pass through us, and shape our experience of the world. Sound waves, light waves, microwaves, Mexican waves – it is easy to forget they are waves at all. Waves also have a great bearing on our atmosphere: from the way light waves are diffracted and refracted by the water droplets and crystals to produce glorious halo phenomena to the way sound waves seem to travel further in foggy conditions as they are bent by the low cold air; from the standing waves of air that cause lenticularis clouds to appear in the lee of mountain peaks to the shearing winds that lead to beautiful undulatus and Kelvin-Helmholtz wave formations. So important are waves to our experience of our surroundings that it is only natural for a cloudspotter to be a wavewatcher too.
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| The Antarctic Ozone Hole and its Discovery |
| Dr Jonathan Shanklin |
British Antarctic Survey |
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14:30, Friday 9 November 2012 | | Physics Seminar Room (Building 46/5081) |
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The talk will outline the scientific steps leading up to the discovery of the Antarctic ozone hole and follow its subsequent evolution, as well as illustrating the Antarctic environment. Climate change and the ozone hole interact, but whilst international measures to combat ozone depletion are working, those designed to reduce emissions of other greenhouse gases are finding less ready acceptance. Dr Shanklin will conclude by pointing out a common cause linking these and other environmental issues.
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| Crystal Structure Engineering in Nanowires |
| Prof Erik Bakkers |
Eindhoven University of Technology |
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14:30, Friday 2 November 2012 | | Physics Seminar Room (Building 46/5081) |
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Important semiconductors like Si, Ge and GaP cannot be used for optical devices, since they have an indirect bandgap when having the (normal) cubic crystal structure. It has been predicted that when these materials crystallize in a hexagonal structure that they can have a direct bandgap. But, these materials have never been made with the wurtzite structure. Nanowires can be grown in other crystal structures than known in the bulk, offering new routes to tailor the optical and electronic properties. Prof Bakkers will discuss the nanowire growth mechanism, investigations of the fabrication of the pure hexagonal form, and the control of the nanowire crystal structure that these possibilities permit. Finally, he will demonstrate the direct nature of the bandgap of wurtzite GaP, which is promising to boost the efficiency of white-emitting LEDs.
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| Ring-Shaped Traps for Atom Interferometry |
| Dr Paul Griffin |
University of Strathclyde |
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14:30, Friday 19 October 2012 | | Physics Seminar Room (Building 46/5081) |
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Atom interferometry offers significant benefits to the field of precision metrology due to the sensitivity to external electromagnetic fields and inertial forces, whilst permitting significantly longer interaction times compared to optical sensors. The Strathclyde group has been manipulating atoms in ring traps for over a decade, with the goal of harnessing the sensitivity of massive quantum particles - atoms - for next-generation sensors. In this talk, Dr Griffin will give an introduction the power of atom interferometry and describe the Strathclyde group's approach, which uses some old physics to overcome previous limitations and to push towards a precise measurement of the fine-structure constant.
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| The Technical Examination and Analysis of Old Master Drawings |
| Mr David Saunders |
British Museum |
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14:30, Friday 12 October 2012 | | Physics Seminar Room (Building 46/5081) |
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Although the technical examination of easel paintings is a well-developed field, various constraints have made it much more difficult to apply similar methods to the examination of Old Master drawings. This talk will look briefly at the issues associated with investigating drawings and watercolours and present the techniques that are used. The results that can be obtained will be illustrated through case studies on Italian Renaissance drawings and English Elizabethan watercolours conducted at the British Museum over the last five years, including as-yet-unpublished findings from a late-sixteenth century map of North America.
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| Navigating to the Moon - challenges faced by Apollo 11 |
| Mr Pat Norris |
Logica (formerly TRW/Apollo moon landing program) |
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14:30, Friday 15 June 2012 | | Physics Seminar Room (Building 46/5081) |
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The first manned lunar landing was a close run thing - Neil Armstrong burned up most of Apollo 11's spare fuel avoiding the rugged terrain NASA had mistakenly navigated him to. Pat Norris was involved in preparing the Apollo 11 navigation and will explain how advances in timing, geodesy and gravity were needed to make the Apollo missions a success - Armstrong presented him with the Apollo Individual Achievement Award for his contribution to the success.
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| Physics and Technology of High-Energy Linear Electron-Positron Colliders |
| Prof Phil Burrows |
John Adams Institute, University of Oxford |
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14:30, Friday 8 June 2012 | | Physics Seminar Room (Building 46/5081) |
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A high-energy electron-positron collider would provide a facility for exploitation of major physics discoveries expected at the Large Hadron Collider at CERN, for example via a 'Higgs boson factory'. The International Linear Collider (ILC) is the most mature design and is aimed at energies of 500-1000 GeV. The Compact Linear Collider (CLIC) is based on a novel 'two-beam' acceleration scheme and targets potentially higher energies, up to multi-TeV. Prof Burrows will review the physics potential of such colliders and discuss the technology challenges along the road to their realisation.
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| Identification and Non-Destructive State Detection of Molecular Ions |
| Dr Matthias Keller |
University of Sussex |
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14:30, Friday 25 May 2012 | | Physics Seminar Room (Building 46/5081) |
Cold molecules have applications ranging from high resolution spectroscopy and tests of fundamental theories to cold chemistry and, potentially, quantum information processing. Prerequisite for these applications is the cooling of the molecules' motion and its non-invasive identification. Furthermore, the internal state of the molecules needs to be prepared and non-destructively detected.
The cooling of the motion and trapping of molecular ions can be accomplished by trapping them in an rf-trap alongside laser cooled atomic ions. Dr Keller will describe a novel technique to measure the average charge-to-mass ratio of trapped ions, which has been employed to observe charge exchange reactions between calcium isotopes, and to characterize the trap anharmonicity with precision. The method is limited only by the required interrogation time and the motional coupling of the constituents of the mixed ion crystal. By employing state-selective laser-induced dipole forces, Dr Keller's group aims to detect the internal state of molecular ions by mapping the state information onto the ions' motion. The scheme promises mitigation of a number of experimental artefacts and may be applicable to large numbers of simultaneously trapped molecules.
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| BFG Composite Rotations: precise control in an imprecise world |
| Prof Jonathan Jones |
University of Oxford |
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14:30, Friday 18 May 2012 | | Physics Seminar Room (Building 46/5081) |
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Quantum information processing technologies are notoriously vulnerable to the effects of errors. These include not only random errors (decoherence) but also systematic errors arising from experimental imperfections. Composite rotations, originally developed in NMR where they are called composite pulses, provide an effective way of tackling systematic errors in many cases, allowing precise control of quantum systems with ordinary imprecise equipment. After a simple introduction to the basic ideas, Prof Jones will describe BB1 composite rotations, and finally the recently discovered family of BFG rotations which allows extreme tolerance of errors in certain cases.
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| Is Quantum Theory Exact? Collapse models and the possibility of a breakdown of quantum mechanics towards the macroscopic scale |
| Dr Angelo Bassi |
University of Trieste |
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14:30, Friday 11 May 2012 | | Physics Seminar Room (Building 46/5081) |
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This talk will review the problems quantum mechanics encounters when describing measurement situations (more generally, the quantum-to-classical transition) and the solutions which have been proposed so far. Dr Bassi will focus on one such solution: models of spontaneous wave function collapse. He will describe their general features and discuss the lower and upper bounds on their parameters, before reviewing their status as phenomenological modifications of quantum mechanics, whose predictions can be tested experimentally.
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| Cosmology in our Backyard |
| Prof Carlos Frenk |
Durham University |
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14:30, Friday 4 May 2012 | | Physics Seminar Room (Building 46/5081) |
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The LCDM cosmological model accounts for an impressive array of data on the large-scale structure of the universe. On submegaparsec scales, however, the model cannot be tested with the same degree of rigour as on larger scales where microwave background radiation data and measures of galaxy clustering provide clean and well-understood diagnostics. Yet, it is precisely on these small scales that the nature of the dark matter manifests itself most clearly. Prof Frenk will discuss theoretical predictions for the small-scale structure of the universe which appear to be discrepant with recent kinematical data for satellite galaxies of the Milky Way. Possible solutions range from exotic baryonic processes to the more radical assumption that the dark matter is not what the standard theory assumes.
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| Nanoplasmonic Field-Enhanced High Harmonic Generation at MHz Repetition Rates |
| Dr Sarah Stebbings |
Max Planck Institute for Quantum Optics |
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14:30, Friday 27 April 2012 | | Physics Seminar Room (Building 46/5081) |
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Laser driven high harmonic generation is a well established technique for the production of attosecond pulses in the extreme ultraviolet (XUV). In this talk, Dr Stebbings will present the different approaches employed in order to generate trains of and isolated attosecond XUV pulses at MHz repetition rates. These sources have potential to open up new applications in lithography, nanoplasmonics, high-precision spectroscopy and time-resolved coincidence experiments.
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| Quantum Nanophotonics |
| Prof Peter Lodahl |
University of Copenhagen |
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14:30, Friday 20 April 2012 | | Physics Seminar Room (Building 46/5081) |
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Nanophotonics structures such as photonic crystals or plasmon nanostructures have in recent years proven to provide a very efficient way of enhancing the local interaction between light and matter enabling all-solid-state quantum electrodynamics experiments. This talk will review recent progress on 2D photonic crystal membranes containing quantum dots for photon emission control, and discuss how a highly efficient and triggered single-photon source can be constructed by coupling single quantum dots to a photonic crystal waveguide by exploiting slow light. The role of disorder in the form of fabrication imperfections is explored and found to lead to Anderson localization of light enabling cavity quantum electrodynamics by exploiting disorder as a way to enhance light-matter interactions. Finally, it will be demonstrated that the mesoscopic character of quantum dot emitters implies that the traditional point-dipole description of light-matter interaction may break down in plasmonic nanostructures, providing a new way to strongly interface photons with matter.
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| Peptide-Functionalised Nanomaterials for Biosensing and Other Applications |
| Prof Molly Stevens |
Imperial College, London |
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14:30, Friday 9 March 2012 | | Physics Seminar Room (Building 46/5081) |
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This talk will cover the Imperial College group's recent work in the design of peptide-functionalised nanoparticles responsive to a plethora of different enzymes. Self-assembling materials can also be utilised successfully in regenerative medicine as will be illustrated here.
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| Organic Semiconductors: lighting up the future |
| Prof Ifor Samuel |
University of St Andrews |
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14:30, Friday 2 March 2012 | | Physics Seminar Room (Building 46/5081) |
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Organic semiconductors are of growing importance as optoelectronic materials. This talk will introduce the materials and show examples of emerging applications. These include the use of organic light-emitting diodes to enable skin cancer treatment, and the detection of explosive vapour using organic semiconductor lasers.
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| Positron Annihilation in Molecules |
| Dr Gleb Gribakin |
Queen's University, Belfast |
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14:30, Friday 24 February 2012 | | Physics Seminar Room (Building 46/5081) |
It has been known since 1950's that positron annihilation rates in many polyatomic molecules can be orders of magnitude greater than estimates based on Dirac's electron-positron annihilation rate. This phenomenon remained one of the major puzzles of positron physics for decades. Dr Gribakin's talk will review the results of concerted efforts by experiment and theory over the past ten years, which have provided much understanding and revealed many interesting details.
As we now know, the enhancement of positron annihilation is caused by positron capture in vibrational Feshbach resonances. This capture is facilitated by the ability of the positron to bind to many neutral atomic and molecular species. The annihilation probability is further enhanced by processes of intramolecular vibrational energy redistribution which increases the positron resonant trapping time.
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| Novel Ion Traps for Deterministic Ion Implantation and Quantum Simulation |
| Dr Kilian Singer |
University of Mainz |
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14:30, Friday 17 February 2012 | | Physics Seminar Room (Building 46/5081) |
Novel geometries of ion traps allow the deterministic, high resolution implantation of individual laser-cooled ions, and can operate with a huge range of sympathetically cooled ion species, isotopes or ionic molecules. They therefore offer the basis of an atomic nano-assembler - a novel device capable of placing an exactly defined number of atoms or molecules with millikelvin energies into solid state substrates with sub-nanometre precision in depth and lateral position.
Motivated by the general quest for novel tailored solid-state quantum materials, the Mainz group's major goal is the deterministic generation of colour centres or quantum dots that can be placed in special geometries to exploit their mutual coupling for the realization of macroscopic functional systems and interfaced to the macroscopic world with the help of electrode structures, single electron transistors and optical micro-cavities. Current state-of-the-art production techniques are incapable of such structures, posing a major production problem for the realization of scaled solid-state quantum devices. Targeted applications range from quantum repeaters, correlated triggered multi-photon sources and calibrated single photon sources to quantum computation circuits and sensors with unprecedented sensitivity.
Dr Singer will also present new planar and three-dimensional trap geometries which allow for the application of variable rf fields for precise positioning of ions in two dimensions. These geometries are of great interest for realizing two-dimensional ion crystals with controllable interactions, and enable novel schemes for the quantum simulation of solid-state spin systems with laser-cooled trapped ions. Dr Singer will also present a novel trap design for the realization of a thermodynamic heat engine with a single ion; simulations and the experimental setup will be shown.
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| Satellite-Based Research on Planetary Waves in the Ocean |
| Dr Paolo Cipollini |
National Oceanography Centre, University of Southampton |
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14:30, Friday 10 February 2012 | | Physics Seminar Room (Building 46/5081) |
We know from Carl-Gustav Rossby's 1930s theory of planetary waves that they should exist not only in the atmosphere (where they are easily seen) but also in the oceans. However, until the advent of precise satellite altimetry in the 1990s, there was very scarce observational evidence. Altimetry has confirmed that these long-wavelength, westward-propagating internal waves are common in the tropical and mid-latitude ocean, where they accompany the ubiquitous non-linear eddies, and that they travel faster than expected – so theoreticians have had to make some adjustments to the theory. But then we started looking in other global satellite-derived datasets (SST, ocean colour), and the signature of eddies and waves is also clearly visible there - implying that these westward-propagating phenomena affect the heat balance and the biology. All these new observations have opened a number of intriguing questions that are not only important for our full understanding of ocean dynamics, but also linked to climate change and the carbon cycle.
In this talk, Dr Cipollini will review what we know, explain what are the many issues still open in this field of research, that need to be tackled with an integrated, interdisciplinary effort, and provide an update on recent work carried out at the National Oceanography Centre on this topic.
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| Next-Generation Quantum Computers |
| Dr Mike Brownnutt |
University of Innsbruck |
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14:30, Friday 20 January 2012 | | Physics Seminar Room (Building 46/5081) |
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Schrödinger bemoaned the fact that one could never perform experiments on single atoms. Nonetheless, in the 20 years since quantum computing was first proposed we have shown that we can actually do exactly that; we have superb control of single atoms, and can perform a variety of basic computational operations on them. Unfortunately, we now face the inverse problem: a computer does consist of single atoms, but of many hundreds or thousands of atoms (at least)! After reviewing how far quantum computing has been carried to date using trapped ions, Dr Brownnutt will look at the question, "Where do we go from here?" What steps must be taken to take the "ridiculous consequences" of quantum mechanics which Schrödinger feared, and preserve them even as we scale computers to such sizes that they are useful? Achieving this scaling in trapped-ion systems requires a radical rethink of how we make and operate traps, but will pave the way to the next generation of quantum computers.
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| Physics Meets Biology: the physical properties of the cell membrane |
| Prof Peter Winlove |
University of Exeter |
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14:30, Friday 13 January 2012 | | Physics Seminar Room (Building 46/5081) |
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Research at the interface between physical science and biology is developing rapidly and studies on the cell membrane demonstrate the importance of this multidisciplinary approach. The textbook view of the membrane as "proteins floating in a sea of phospholipids" (Singer and Nicholson (1970)) fails to address important issues such as the diversity of lipids found in the membrane. We shall begin by discussing studies on Langmuir monolayers of phospholipids which explore the physics of interactions between lipid classes and with cytoskeletal proteins. We shall then introduce novel techniques for measuring the unique mechanical properties of the membrane and present evidence of changes in red cell mechanics that may be important in disease. Finally we shall discuss the complex electrical properties of the membrane, their characterisation by means of fluorescence microscopy, and their importance in membrane function and dysfunction.
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| Single-Site-Resolved Detection and Manipulation of Atoms in an Optical Lattice |
| Prof Stefan Kuhr |
University of Strathclyde |
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14:30, Friday 16 December 2011 | | Physics Seminar Room (Building 46/5081) |
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Ultracold atoms in optical lattices are a versatile tool to investigate fundamental properties of quantum many body systems. Prof Kuhr will demonstrate how the control of such systems can be extended down to the most fundamental level of single atomic spins at specific lattice sites. Using a high-resolution optical imaging system, fluorescence images have been obtained of strongly interacting bosonic Mott insulators with single-atom and single-site resolution and addressed the atomic spins with sub-diffraction-limited resolution. In addition, the tunneling quantum dynamics of single atoms in the lattice have been directly monitored. Most recent experiments involve the observation of quantum-correlated particle hole pairs and spreading of correlations after a parameter quench. These results open the path to a wide range of novel applications from quantum dynamics of spin impurities, entropy transport, implementation of novel cooling schemes, and engineering of quantum many-body phases to quantum information processing.
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| Nanoplasmonics: fundamentals & applications |
| Prof Stefan Maier |
Imperial College, London |
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14:30, Friday 2 December 2011 | | Physics Seminar Room (Building 46/5081) |
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This talk will give an overview over recent research in the Nanoplasmonics group at Imperial College London. The first part will focus of fundamental investigations of localised plasmons in metallic nano particles, in particular approaching the quantum limit with nano antennas, non-local effects, and the creation of broadband light harvesters using transformation optics. The second part of the seminar will discuss applied studies in photovoltaics, biosensing, and a new application of plasmonic – plasmonic sinks for the selective removal of unwanted states in nanoscale light emitters.
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| Quaternary Nanocrystals: synthesis and energy applications |
| Dr Andreu Cabot |
University of Barcelona and
Catalonia Institute for Energy Research |
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14:30, Friday 25 November 2011 | | Physics Seminar Room (Building 46/5081) |
The control of material composition at the nanoscale is essential to the optimization of the characteristics of novel nanomaterials and their performance in applications such as photovoltaics, catalysis and thermoelectrics. In bottom-up synthesis aproaches, nanocrystal composition is determined by the thermodynamics and reaction kinetics of the different precursors, with self-diffusivity playing a key role.
Colloidal synthesis has proved a successful method of obtaining elemental and binary nanocrystals with controlled size and shape distributions, but ternary and quaternary nanocrystals remain a challenge. Dr Cabot will describe current efforts to achieve this step-change in the chemical and structural engineering of functional nanomaterials, which promises to open up the technological potential of quaternary chalcogenides in a range of photonic, optoelectronic, magnetic and chemical applications.
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Measuring Hotter than the Centre of the Sun:
diagnosing the temperature of the ITER plasma |
| Dr Graham Naylor |
Culham Centre for Fusion Research |
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14:30, Friday 18 November 2011 | | Physics Seminar Room (Building 46/5081) |
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The surface of the sun has a temperature of about 6 thousand Kelvin, and its centre is estimated to be at around 15 million Kelvin; in comparison, the centre of the plasma of the International Thermonuclear Experimental Reactor (ITER) is expected to be several hundred million Kelvin. How can this be measured? Laser Thomson Scattering is used routinely around the world to measure the temperature of tokamak plasmas and is expected to be used on ITER but on a scale never achieved before.
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| Graphene for Photonics and Optoelectronics |
| Prof Andrea Ferrari |
University of Cambridge |
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14:30, Friday 11 November 2011 | | Physics Seminar Room (Building 46/5081) |
The richness of optical and electronic properties of graphene attracts enormous interest. Graphene has high mobility and optical transparency, in addition to flexibility, robustness and environmental stability. It has great potential for photonics and optoelectronics, where the combination of its unique optical and electronic properties can be fully exploited, even in the absence of a bandgap, and the linear dispersion of the Dirac electrons enables ultra-wide-band tunability.
Despite being a single atom thick, graphene can be optically visualized. Its transmittance can be expressed in terms of the fine structure constant. The linear dispersion of the Dirac electrons enables broadband applications. Saturable absorption is observed as a consequence of Pauli blocking. Chemical and physical treatments enable luminescence. Graphene-polymer composites can be integrated in laser cavities, to generate ultrafast pulses, to below 200fs, with broadband tunability.
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| Flexible, Nanofabricated Photonic Crystals: a new class of micromechanical actuator |
| Dr James Bateman |
University of Southampton |
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14:30, Friday 28 October 2011 | | Physics Seminar Room (Building 46/5081) |
Optical tweezers allow precise and delicate control of tiny objects from atoms to biological cells, yet they require intense light and tight focusing. In micro-optics, light is confined by near wavelength-scale structures, and these steep intensity gradients occur automatically. Coupled with optical resonators, which cause the field to build-up within the structure, we can engineer in microfabricated structures the ideal conditions for strong optical forces.
This combination of tweezing and microfabrication has spawned the rapidly growing field of optomechanics: toroidal resonators coupled evanescently to waveguides have allowed for table-top frequency combs, and vibrating photonic crystals have been cooled to their quantum-mechanical ground state. Despite the enormous scope of optomechanics, work has thus far been confined to the perturbative regime, where structures move only fractionally from their rest positions: mechanical motion is either an intermediary to affect the light, or is used for quantum mechanical demonstrations. This contrasts starkly with MEMS - micro-electromechanical systems - where microstructures move in response to applied voltages to provide technologically useful real world devices.
Dr Bateman will describe work towards creating an optically-driven equivalent of MEMS: micromechanical devices controlled and driven by light. This new class of microactuator will compliment MEMS in, for example, microfluidics, and it hints at far wider possibilities: freed from the electrical connections which tether MEMS to a substrate, we might create biologically-inspired peristaltic pumps, or even freely-floating microswimmers.
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| Atom Chips: where quantum optics meets material science |
| Prof Ron Folman |
Ben Gurion University |
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14:30, Friday 14 October 2011 | | Physics Seminar Room (Building 46/5081) |
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In this talk, Prof Folman will review the basics of a device called the atom chip in which quantum systems (e.g. ultra cold atoms) are trapped and manipulated microns from the classical environment of a room temperature surface. He will describe the underlying physics governing this combined apparatus (e.g. coupling through the highest temperature gradient ever created in a lab). All this will be detailed in the context of material science which allows engineering of the surface environment so as to accommodate fundamental studies as well as technological applications.
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| Evidence for a Cosmic Battery |
| Dr Denise Gabuzda |
University College, Cork |
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14:30, Friday 7 October 2011 | | Physics Seminar Room (Building 46/5081) |
In a standard theoretical picture of the formation and launching of astrophysical jets, the jets should acquire helical magnetic fields, due essentially to the combination of the rotation of the central black hole and accretion disk and the jet outflow. One way such helical fields may be manifest is through their tendency to give rise to gradients in the observed local Faraday rotation across the jet, due to the systematic variation of the line-of-sight component of the helical magnetic field across the jet. Indeed, transverse Faraday rotation gradients have been observed across a number of AGN jets on both parsec and kiloparsec scales, providing direct evidence that they carry toroidal or helical magnetic fields.
The directions of the observed transverse Faraday rotation gradients provide statistical evidence for the operation of a cosmic "battery" in the accretion disks of AGN, which couples the direction of rotation and the direction of the poloidal (axial) field of the jet. If this "battery" is indeed operating, we have detected the presence of ordered currents and magnetic fields on a grand scale.
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| A Large, Dirty, Messy Quantum World? |
| Dr Mauro Paternostro |
Queen's University, Belfast |
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14:30, Friday 30 September 2011 | | Physics Seminar Room (Building 46/5081) |
Quantum mechanics is difficult. Even the most experienced among us will admit the undeniable truth of this claim. Yet, the quantum framework is endowed with such a degree of accuracy that it has embodied a genuine conceptual revolution in the way we explain and understand Nature at the microscopic and level.
By adopting an information-theoretical viewpoint, Dr Paternostro will in this talk discuss the possibility to extend the applicability of quantum theory up to the point that inherently complicated systems, trespassing the boundaries of the clean and protected micro-world, can exhibit truly quantum features, thus entering what may be called "the mesoscopic quantum domain".
Dr Paternostro will discuss in depth the technological implications of such a paradigm shift and demonstrate that the control that is currently available in photonics and condensed-matter labs is indeed sufficient to build an experimental programme for the demonstration of a "larger, dirtier and messier quantum world"!
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| The Square Kilometre Array |
| Dr Joe Lazio |
JPL |
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14:30, Friday 16 September 2011 | | Physics Seminar Room (Building 46/5081) |
The Square Kilometre Array is intended to be the centimetre- and metre-wavelength telescope for the 21st Century. Originally proposed as the "hydrogen telescope," the science case is now recognized to be much broader, and the SKA will address fundamental questions in astrophysics, physics, and astrobiology.
The international science community has developed a set of Key Science Programs: (1) Emerging from the Dark Ages and the Epoch of Reionization; (2) Galaxy Evolution, Cosmology, and Dark Energy; (3) The Origin and Evolution of Cosmic Magnetism; (4) Strong Field Tests of Gravity Using Pulsars and Black Holes; and (5) The Cradle of Life & Astrobiology.
Dr Lazio will highlight how the SKA's Key Science Programs will be an integral component of the multi-wavelength, multi-messenger frontiers for astronomy and how the science pathfinding for the SKA is beginning now.
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| High-Speed Optical Quantum Memories |
| Mr Klaus Reim |
University of Oxford |
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14:30, Friday 10 June 2011 | | Physics Seminar Room (Building 46/5081) |
In a globalised world with ever-increasing, intercontinental information exchange, there is growing demand for secure communication technology, such as could be provided by photonic quantum communications networks. Currently, the biggest challenge for such networks is distance. Over short distances, photons, interacting only weakly with their environment, easily and reliably carry quantum information without much decoherence, but intercontinental quantum communication will require quantum repeaters embedded in potentially isolated locations, because photon loss rises otherwise exponentially with distance. In general, these repeaters will require some sort of quantum memory, a coherent device where single photons are reversibly coupled into and out of an atomic system, to be stored, possibly processed and then redistributed. In order to be practically useful, this will need to have sufficiently large bandwidth, high efficiency and long storage time, with multimode capacity, and a low-enough noise level to enable operation at the quantum level.
Dr Reim will talk about an ensemble-based, far off-resonant Raman approach to quantum memories, describe how the interaction mechanism works and show how a single photon level signal may be stored in the quantum memory and retrieved at a controlled later point in time. Furthermore, he will address de-phasing mechanisms for the stored spin-wave excitation that limit storage times and discuss storage and retrieval of polarization-encoded qubits.
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| Ion Coulomb Crystals: classical and quantum effects at the linear-zigzag transition |
| Prof Giovanna Morigi |
Universität des Saarlandes |
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14:30, Friday 27 May 2011 | | Physics Seminar Room (Building 46/5081) |
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A string of trapped, cold ions exhibits a structural phase transition to a zigzag structure, which can be tuned by adjusting the trap potentials and particle number. This proves to be a quantum phase transition, which can be mapped onto that of an Ising chain in a transverse field, and has a measurable deviation from the classical prediction. Three-dimensional Coulomb crystals of cold, trapped ions constitute a fascinating physical realization of the phenomena discussed by Wigner for electrons in metals, can be experimentally realized and probed, and have potential applications in quantum simulators and other quantum technologies.
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| An Ion Trap in a Silicon Chip: a component for atomic quantum technologies |
| Dr Alastair Sinclair |
National Physical Laboratory |
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14:30, Friday 20 May 2011 | | Physics Seminar Room (Building 46/5081) |
Scalability of atomic systems for quantum technologies is a significant challenge. To address this, microfabrication techniques are increasingly used to realise chip-based architectures for confining atomic particles.
The NPL team has developed a microfabricated ion trap chip using scalable processing techniques, based on gold-coated, oxidised silicon. This trap possesses a unique set of credentials and is now operational. Confined in the deep potential afforded by the 3D monolithic structure, ions exhibit motional frequencies of a few MHz and a low heating rate. While first devices consist of only a few trapping segments, the fabrication process will enable devices containing a complex array of many electrodes.
This talk will describe the fabrication and elementary operation characteristics of the chip-scale ion trap. Applications prospects for the device, which include quantum metrology & sensors, and quantum processors & networks, will be discussed.
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| New Adventures in Ultrafast and Single Molecule Optics |
| Dr Philipp Kukura |
University of Oxford |
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14:30, Friday 13 May 2011 | | Physics Seminar Room (Building 46/5081) |
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Dr Kukura will discuss recent developments in the application of laser-based techniques to directly visualise and thereby study dynamic processes occurring on vastly different time and size scales in chemistry and biology. The first part of the talk will focus on combined experimental and theoretical efforts based on ultrafast spectroscopy aimed at revealing atomic motion on its intrinsic, femtosecond, time scale. Specifically, it will address the structural changes occurring during the primary step in vision, the 11-cis to trans isomerization of the retinal chromophore in the visual pigment rhodopsin, and its implications for rhodopsin reactivity and efficient photochemistry in general. The second part will introduce a novel microscopic imaging technique based on interferometric scattering (iSCAT) and illustrate its use for high-speed, three-dimensional nanometric tracking of nanometer-sized objects. Particular attention will be geared towards recent results on the nanoscopic motion of individual virions diffusing on artificial membranes as well as the extension of iSCAT towards label-free sensing and the first detection and imaging of single molecules in absorption.
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| The Molecular Mechanism of Respiration |
| Ms Philippa Roberts |
University of Cambridge |
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14:30, Friday 6 May 2011 | | Physics Seminar Room (Building 46/5081) |
Synthesis of the biological molecular 'energy carrier' ATP is driven by a mitochondrial electrochemical gradient, in which the transfer of electrons between donors and accepters is coupled to the transfer of H+ ions (protons). The biological catalytic cycles are fairly well understood, in so much as we know which chemicals react with which enzymes, but the molecular mechanism of electron transfer and proton translocation remains something of a puzzle.
Some of the mechanisms most likely involve coherent quantum hopping of electrons through a chain of iron-sulphur clusters and a conformational change that drives proton transport across the mitochondrial inner membrane. This talk discusses recent advances towards understanding the proton translocation mechanism and electron transport mechanism within the enzyme.
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| Strongly Interacting Photons |
| Prof Charles Adams |
University of Durham |
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14:30, Friday 1 April 2011 | | Physics Seminar Room (Building 46/5081) |
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The control of light at the few photon level is compromised by the absence of sufficiently large optical non-linearities. To overcome this limitation, photons may be mapped into atomic Rydberg excitations that have extremely large dipole-dipole interactions. The interaction between Rydberg atoms creates a photon blockade, leading to a large non-linearity at the single photon level.
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| The Hundred Year Hunt for the Red Sprite |
| Mr Peter McLeish |
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14:30, Friday 25 March 2011 | | Physics Seminar Room (Building 46/5081) |
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This presentation documents one of the most unexpected atmospheric scientific findings of the late 20th century. For over a century, people – including well-respected scientists – had reported seeing strange lights in the night sky about thunderstorms. But it remained until a "happy accident" in 1989 for the first such event to be captured on video tape with a low-light camera. One researcher exclaimed it was as if Biology had just suddenly discovered a new human body part. Since then, an entire "zoo" of luminous creatures has been found in the thin air above thunderstorms – and discoveries are still being made. The presentation also examines how the public can become engaged in the search for new thunderstorm-related electrical phenomena.
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| Optical Nanofibres for Probing and Manipulating Particles |
| Dr Sile Nic Chormaic |
University College, Cork |
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14:30, Friday 18 March 2011 | | Physics Seminar Room (Building 46/5081) |
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Dr Nic Chormaic will discuss tapered optical fibres of subwavelength diameter, including their fabrication and use in a range of experiments, and will explore how dark nanofibres can be used to probe the characteristics of laser-cooled atoms and how bright nanofibres are used to study surface interaction effects between the atoms and the fibre surface. Finally, she will consider higher order mode propagation within an optical fibre and discuss how this could be used to generate ordered arrays of trapping sites around the fibre for cold atoms or colloidal particles.
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| The Size of the Proton |
| Dr Randolf Pohl |
Max Planck Institute for Quantum Optics |
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14:30, Friday 11 March 2011 | | Physics Seminar Room (Building 46/5081) |
The proton charge radius Rp has recently been determined by means of laser spectroscopy of the exotic "muonic hydrogen" atom with ten times higher accuracy than the present CODATA value of Rp - but 5 sigma away from it. It is not yet clear how this discrepancy has to be interpreted. Ultimately, the result could question the validity of the most precisely tested fundamental theory of matter and light, or change the value of the most precisely determined fundamental physical constant.
The muon, which is the 200 times heavier cousin of the electron, orbits the proton with a 200 times smaller Bohr radius compared to regular hydrogen. This enhances the sensitivity to the proton's finite size tremendously.
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| A Physicist in Finance |
| Dr Dean Read |
IMC Financial Markets, Amsterdam |
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14:30, Friday 25 February 2011 | | Physics Seminar Room (Building 46/5081) |
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For a couple of decades there has been a flow of doctorate level physicists to the financial services industry. This talk aims to provide some insight into what these so called ‘Rocket Scientists' are doing and why their physics background is even relevant in an arena where the only goal is to buy low and sell high.
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| The Physics of Snow |
| Dr Paul Connolly |
University of Manchester |
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14:30, Friday 18 February 2011 | | Physics Seminar Room (Building 46/5081) |
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Snowflakes form when vapour grown ice crystals aggregate together. The rate at which this happens can affect whether snow reaches the ground or not. This talk will cover the physics of snow formation and will present laboratory data of snow formation in the Manchester Ice Cloud Chamber to test our understanding of the efficiency by which ice crystals stick together.
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| Variations on a Theme of Aharonov and Bohm |
| Prof Sir Michael Berry FRS |
University of Bristol |
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14:30, Friday 11 February 2011 | | Physics Seminar Room (Building 46/5081) |
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The partial anticipation of the Aharonov-Bohm (AB) effect by Ehrenberg and Siday was an approximation whose wavefunction was not singlevalued; its connection with the singlevalued AB wave involves a ‘many-whirls representation' in terms of waves winding round the flux line. AB is a fine illustration of idealization in physics. There are four AB effects, depending on whether the waves and the flux are classical or quantum; in the classical-classical case, fine details of the AB wavefunction have been explored experimentally in ripples scattered by a water vortex. The AB wave possesses a phase singularity, and there is a similar phenomenon in general interferometers. There are connections between the AB wave and the Cornu spiral describing edge diffraction. In bound systems, the half-flux case exhibits unexpected energy-level degeneracy structure.
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| Atomic Cooperativity in Cavity Quantum Electrodynamics |
| Dr Jon Goldwin |
University of Birmingham |
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14:30, Friday 4 February 2011 | | Physics Seminar Room (Building 46/5081) |
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Optical cavities can provide a way to enhance the basic interactions between light and matter. Dr Goldwin will discuss experiments where microfabricated Fabry-Perot resonators are used to detect clouds of cold atoms at densities below one atom per cavity mode volume. It is observed that the signal fluctuations due to random atom numbers and positions are heavily suppressed, leaving photon counts near the shot noise limit. This noise reduction may be traced back to the nonlinear interaction of the collective atomic dipole with the quantum optical field of the cavity.
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| Gyrocopters |
| Mr Steve Boxall |
The Gyrocopter Experience |
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14:30, Friday 28 January 2011 | | Physics Seminar Room (Building 46/5081) |
Invented by Spanish engineer Juan de la Cierva and first flown in 1923, the gyrocopter or autogiro is best known to most from the 1967 Bond film You Only Live Twice. Unlike the helicopter which uses its engine to power the lift-generating rotor directly, the gyrocopter has a freely-rotating rotor whose blades act like the wings of a glider, the aircraft being maintained in flight by the horizontal thrust from a conventional propeller. The result is a simple aircraft with much of the manoeuvrability of a helicopter, which requires a (short) ground run to become airborne but can achieve a near-vertical descent to land.
Recent refinements to classical designs have brought a new generation of commercially-produced two-seat aircraft that have propelled the gyrocopter from the domain of the quirky enthusiast to the mainstream, and gyrocopter schools are opening across the country. Steve Boxall - a gyrocopter pilot for over a decade and flight instructor for over 20 years - is the chief instructor of the Gyrocopter Experience at Old Sarum; in this talk, he will describe both the principles and joys of gyrocopter flight.
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| Accelerators - Giant or Compact - for Science, Industry and Society |
| Prof Andrei Seryi |
John Adams Institute for Accelerator Science |
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14:30, Friday 21 January 2011 | | Physics Seminar Room (Building 46/5081) |
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Accelerator science is a key element for discoveries in high energy physics, and is a crucial source for many advances in biology, medicine, solid state physics, future energy production, and various other fields. The size of facilities spans from international mega projects to university-scale installations. Interdisciplinary research on the boundaries of accelerator, laser, and plasma physics will revolutionize the entire landscape of accelerator science and open possibilities for stronger connections to industries. The modern trends in accelerators and compact X-ray and THz sources will be discussed in the context of future plans of the John Adams Institute for Accelerator Science, as well as within the national and international context.
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| Exploring Strongly Correlated Quantum Matter in Artificial Crystals of Light |
| Prof Immanuel Bloch |
Max Planck Institute for Quantum Optics
Ludwig Maximilians University, Munich |
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14:30, Friday 10 December 2010 | | Physics Seminar Room (Building 46/5081) |
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The realization of ultracold quantum gases at Nanokelvin temperatures has marked a milestone in modern quantum physics. With the help of laser light, these ultracold atom clouds can be stored in artificial periodic potentials created by laser light - so called optical lattices - that allow us to explore fundamental aspects of strongly interacting fermionic and bosonic quantum matter. In very recent experiments, the Munich groups have been able to record single snapshots of a quantum fluid in which individual atoms are detected with single lattice site resolution. This opens unprecedented novel opportunities for analyzing and manipulating strongly interacting quantum system. In his talk, Prof Bloch will review some of the recent experiments on strongly correlated quantum gases in optical lattices and highlight connections to condensed matter physics, quantum information science and atomic-and molecular physics.
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Focusing and Imaging in Disordered Systems:
why you can see more sharply through a dirty window |
| Dr Allard Mosk |
University of Twente |
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14:30, Friday 26 November 2010 | | Physics Seminar Room (Building 46/5081) |
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In opaque white materials such as paper, paint and biological tissue, light is randomly scattered and loses its direction completely as it diffuses through the system. Dr Mosk's group has shown experimentally that light can be controlled as it propagates within and through such disordered materials. Remarkably, the scattering can even improve control. Phase coherence, and therefore the possibility for the light to show interference phenomena, is not lost by elastic scattering processes. By manipulating the incident wavefront, it is possible to force constructive interference at any point in space and thereby focus light inside and through opaque materials. Wavefront shaping can also drastically change the total transmission through a material, displaying a universal mode of wave transport. Dr Mosk will discuss eigenchannels of the transmission matrix, special wavefronts in which the energy is fully transmitted or fully reflected by a random scattering material. Since the first introduction of wavefront shaping methods in optics of random scattering materials, several exciting new developments have brought the method much closer to practical applications in technology and medicine.
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| How Animals Navigate |
| Air Cdre D F H 'Pinky' Grocott |
Royal Institute of Navigation |
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14:30, Friday 19 November 2010 | | Physics Seminar Room (Building 46/5081) |
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The Monarch butterfly migrates 2,000 to 3,000 km using primarily a sun compass and magnetism, while turtles find the way back to their place of birth after 20 years. These are just two of the extraordinary examples that Air Cdre 'Pinky' Grocott will be using to illustrate the many different techniques that animals use to find their way around - from polarized light and magneto-reception to smell. A past President of the Royal Institute of Navigation (RIN), Air Cdre Grocott has many years experience in both air and animal navigation.
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| The Geonium Chip: a superconducting planar Penning trap for electrons |
| Dr José Verdú-Galiana |
University of Sussex |
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14:30, Friday 12 November 2010 | | Physics Seminar Room (Building 46/5081) |
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Penning ion traps are used in a wide variety of applications, including mass spectrometry, high precision measurements of atomic and nuclear properties and the production of antihydrogen. Originally motivated by recent proposals for the implementation of a quantum processor with trapped electrons, novel, scalable, planar Penning traps have been designed and fabricated, but the observation of a single trapped electron remains an open challenge. The Sussex group has conceived a planar Penning trap technology which allows the capture and efficient detection of a single electron in a design inspired by extraordinary developments in planar microwave technology. Superconducting microwave resonators have been fabricated, and are capable of storing a single photon for a long time, thus permitting the coherent transfer of quantum information between different physical systems within the chip. This has led to a new theoretical approach, known as circuit-quantum electrodynamics (circuit-QED), to describe the interactions of (artificial) atoms and photons using concepts and methods of circuit theory. Dr Verdu-Galiana will describe the novel superconducting Coplanar Waveguide-Cavity Penning Trap and his recently started project to develop a geonium chip where, among other applications, a single trapped electron will become one of the basic building blocks of future quantum circuits.
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| Extracting Structure from Signals |
| Dr Nick Jones |
University of Oxford |
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14:30, Friday 5 November 2010 | | Physics Seminar Room (Building 46/5081) |
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Scientific optimism suggests that the data we collect has an underlying simplicity. Yet experience tells us that detecting this simple structure can be hard. How to select the best method for probing signal structure from a zoo of tools for time series analysis is often very unclear. Dr Jones will discuss a recent, extensive, synthesis of methods for data analysis; this yields a powerful tool for probing not only the empirical structure of signals but also their methods and models. He will then consider how this helps characterize nanopores, epilepsy, bird-song, fractional brownian motion, and detrended fluctuation analysis.
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| Light to Cool, Manipulate and Probe Many-Body Systems with Ultracold Bosons |
| Dr Chiara Fort |
LENS and Università di Firenze |
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14:30, Friday 29 October 2010 | | Physics Seminar Room (Building 46/5081) |
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This talk will describe how laser light is used in current experiments to simulate and study many-body physics using ultracold quantum gases. In particular, after a general introduction, Dr Fort will report on recent experiments performed at LENS where inelastic light scattering is used to probe correlated phases produced by loading a Bose-Einstein condensate into optical lattices.
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| A Fluid Motion Approach to Cosmology |
| Prof Geoffrey Lilley OBE |
University of Southampton |
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14:30, Friday 22 October 2010 | | Physics Seminar Room (Building 46/5081) |
Prior to the explosion of research during the past century on Cosmology, following Einstein's work on Relativity, the fields of Fluid Mechanics and Optics, leading respectively to the propagation of sound and light, were regarded as having much in common since they were governed by the same unique wave equation, even though sound waves were longitudinal and light waves were transverse and travelled a million times faster than sound. It was common to study phenomena such as wave interference using the shallow water ripple analogy tank since shallow water surface waves, sound and light all obeyed the same wave equation, and hence had similar solutions for the same ratio of source speed to wave propagation speed in the appropriate medium: respectively water, air and the ether.
The ether had been introduced as long ago as the Greeks and more recently by Huygens and even Newton to support wave motion in the universe. Its properties were unknown and were stated by Maxwell, in introducing the equations of electromagnetic radiation, as the greatest unknown property of all science. All experiments failed in finding the ether and it was left to Einstein to introduce the postulate that since all attempts to find the ether had failed therefore for all practical purpose it could be assumed not to exist, and that all intergalactic space was a void. Thus at a stroke any connection between the propagation of sound and light was severed, and it was accepted that light could be propagated in a void whereas experiment confirmed that sound could not. The present work explores a possible model for dark matter as a physical realization of an ether of finite density, and its implications for a model of the Universe.
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In-Situ Wavefront Optimization:
a new route to ideal performance of biophotonic systems |
| Dr Tomáš Čižmár |
University of St Andrews |
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14:30, Friday 15 October 2010 | | Physics Seminar Room (Building 46/5081) |
State-of-the-art biophotonics laser systems frequently rely upon high numerical aperture objectives tightly focusing a laser beam, ideally into a diffraction limited spot, the smallest possible area where the total laser power can be concentrated. However, in all optical systems, optical and alignment imperfections result in deleterious aberrations that manifest themselves by an unwanted reduction of the focus intensity and a distribution of the optical power outside the focal volume. Such optical aberrations can be eliminated introducing an adaptive optical element but naturally, the wavefront distortion has to be recognized and properly quantified prior to the compensation being applied.
Dr Cizmar will present a method to eliminate all aberrations including those originating in the sample chamber and restore the optimal focusing of laser light in situ after propagating through a random scattering medium. It will be shown that the optimized spot can be used for optical trapping even for the case of a laser beam passing a very strongly scattering media present within the sample chamber. Other important applications will be demonstrated, including complex beam profiling, enhanced beam shaping, optical trapping with uncorrected optics, or controlling the laser output from a multimode optical fibre.
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Detecting Phase Transitions in Supercritical Mixtures:
an enabling tool for greener chemical reactions |
| Prof Martyn Poliakoff CBE, FRS |
University of Nottingham |
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14:30, Friday 8 October 2010 | | Physics Seminar Room (Building 46/5081) |
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Detecting phase transitions in high-pressure CO2 and supercritical fluids was first attempted in the nineteenth century. By contrast, Green Chemistry, the design and implementation of cleaner methods of manufacturing and processing chemicals, is barely 20 years old. Now, the use of CO2 as an environmentally more acceptable replacement for traditional solvents for greener chemical reactions is creating the need for new, more rapid methods for elucidating high-pressure phase behaviour. This lecture outlines some approaches, developed in Nottingham, to meet this need, including shear-mode quartz sensors, the fibre-optic reflectometer and pressure drop measurements.
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| Controlling and Interfacing Atoms and Light |
| Prof Axel Kuhn |
University of Oxford |
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14:30, Friday 18 June 2010 | | Physics Seminar Room (Building 46/5081) |
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In the endeavour of constructing a quantum computer, a major challenge is to couple and control a large ensemble of identical quantum systems at the single-particle level. In this colloquium, Prof Kuhn will first show how to interface single atoms with single photons in high-finesse optical resonators, and then introduce his group's approach of manipulating these atoms with an array of optical tweezers. These two approaches are the keys to scalable quantum networks, which one could use for quantum computing or simulation.
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| Using Mathematical Models to Plan for Outbreaks of Plague |
| Dr Ian Hall |
Health Protection Agency |
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14:30, Friday 11 June 2010 | | Physics Seminar Room (Building 46/5081) |
The plague caused by the bacterium yersinia pestis is reckoned to have caused 200 million deaths since it was first recorded devastating the Byzantine empire in the sixth century, to have wiped out at least a quarter of the population of Europe as the Black Death in medieval times, and to have killed a fifth of London's population in the Great Plague of 1665-6. Spread then by fleas as an infection of the lymph nodes (buboes, hence bubonic), the plague can also infect the lungs and be spread directly from person to person through coughs and sneezes. Pneumonic plague is regarded as one of the most likely diseases to be used in a modern bioterrorism attack, and its epidemiology is therefore keenly studied.
Dr Hall will discuss the nature of this unpleasant and often fatal disease, how it is transmitted, its eco-epidemiology, and the crucial part played, when it occurs in modern society, by human perceptions and responses to it. He will outline some conclusions from epidemiological studies suggesting helpful strategies for managing any outbreaks, and will describe the role of the Health Protection Agency and other agencies in planning for and management of such events. The talk will be lavishly illustrated.
The Microbial Risk Assessment group, within the Health Protection Agency, is tasked with providing evidence based advice relating to new and emerging infections. Plague, in its various forms, is an endemic disease in parts of the world and is fatal in almost all untreated cases. As such it is a risk to public health and this presentation considers the effect of natural disease importation on wildlife ecology, the impact of small numbers of human cases of pneumonic plague and the control of larger releases. Whilst evaluating the control of larger releases we analyse the results from a behavioural survey on public reaction to plague releases. The evidence base for assumptions and parameterisation of models when used to inform contingency plans must be critically appraised.
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| Sixty Years On Ice |
| Dr Charles Swithinbank |
British Antarctic Survey & Scott Polar Research Institute |
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14:30, Friday 28 May 2010 | | Physics Seminar Room (Building 46/5081) |
Charles Swithinbank is the first person to have an unbroken career in polar research from graduation to retirement. His first Antarctic expedition at the age of 22 led to an Oxford D.Phil in glaciology. He went on to work in Arctic Canada before enjoying 26 years with the Scott Polar Research Institute, the British Antarctic Survey, the U.S Antarctic Program and the Soviet Antarctic Expedition. He has voyaged to the North Pole in a submarine and has worked at the South Pole.
Dr Swithinbank is the author of four volumes of autobiography.
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| Quantum Gases - quantum simulation and precision sensors |
| Prof Kai Bongs |
University of Birmingham |
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14:30, Friday 21 May 2010 | | Physics Seminar Room (Building 46/5081) |
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Ultracold atomic gases offer a pristine resource for the study of fundamental quantum phenomena as well as the realization of ultraprecise sensors. The talk will present an introduction to cold atom physics and optical lattices. Here the bosonic superfluid to Mott insulator transition is one groundbreaking example of the possibility to simulate one quantum system with another one. On the applied side the talk will discuss quantum sensors based on atom interferometry and some technological developments in the area of quantum gases in space.
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| First Results from the LHC |
| Mr Matt Coombes |
University of Southampton |
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14:30, Friday 14 May 2010 | | Physics Seminar Room (Building 46/5081) |
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With the Large Hadron Collider colliding particles at record energies since the end of 2009, there has been a great interest from the world's media and scientists. This talk aims to give a simple introduction to the exciting physics currently taking place at the LHC. Each of the four main experiments on the LHC ring will be introduced. The physics aims of each experiment will be discussed with a look at the new physics that may be observed at energy levels that only the LHC is capable of probing. A performance update of the LHC since its 2009 start up will also be given.
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| Polymer Solar Cells |
| Prof Neil Greenham |
University of Cambridge |
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14:30, Friday 7 May 2010 | | Physics Seminar Room (Building 46/5081) |
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Solar energy is ubiquitous, but for solar cells to contribute a significant reduction in carbon emissions they need to be cheaper than the current silicon technology and capable of being produced over vast areas. Solar cells based on semiconducting polymers are therefore attractive since they can be produced by roll-to-roll printing onto flexible substrates. The efficiencies of these cells are improving rapidly, but are still not high enough for large-scale application. Prof Greenham will describe some of the science surrounding organic solar cells, addressing the issues of how to separate charges in an organic semiconductor, how to reduce recombination losses, and how to image and control nanostructures on the nanometre lengthscales required.
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| Insects on Rubber and Dogs on Springs: sensing and perturbing animals to understand the mechanics and control of legged motion |
| Dr Andrew Spence |
Royal Veterinary College |
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14:30, Friday 30 April 2010 | | Physics Seminar Room (Building 46/5081) |
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One of the grand challenges in organismal biology is to understand how the nervous system produces locomotion. Animals move quickly through heterogeneous, three dimensional environments with stability and economy that far surpass our technology. This talk will present work that seeks to discover the control targets used by fast running, legged animals to achieve their remarkable performance. Results from insects and dogs running over soft surfaces will be presented, suggesting that many-legged runners use a different strategy than that of bipedal runners to compensate for soft surfaces. Yet the intriguing possibility exists in both systems that sinking into a surface may simplify the task for the neural controller, because of the mechanics of leg posture on foot touchdown. The implications of these results for the hypotheses of low-dimensional mechanical templates as targets of control, and of dimensional reduction in sensorimotor control, will be discussed. The integrative nature of this work, drawing on biology, physics, dynamical systems and control theory, as well as robotics, will be highlighted.
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| Synthesis, Emergence and New Properties of Hybrid Nanoscale Objects |
| Prof Steve Mann |
University of Bristol |
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14:30, Friday 23 April 2010 | | Physics Seminar Room (Building 46/5081) |
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Organized-matter chemistry is concerned with the synthesis, characterization and application of complex materials that exhibit order on length scales from the molecular to macroscopic. Recently, new strategies have been developed for the integration of organic self-organization and inorganic assembly such that hybrid nanoscale objects and nanostructures can be constructed by equilibrium (bottom-up templating) or non-equilibrium processes (synergistic emergence). These principles will be illustrated using several examples of the Bristol group's most recent work including the co-assembly of block copolymer/titania (silica) nanowires, synthesis of metallic nanowires arrays within cross-linked protein crystals, reconstitutive co-assembly of graphene/DNA nano-hybrids and the unprecedented formation of solventless liquid proteins at room temperature.
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| Sustainable Energy - the IMechE UK Energy Plan for 2050 |
| Dr Alison Cooke |
University of Cambridge & Cooke Associates |
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14:30, Friday 19 March 2010 | | Physics Seminar Room (Building 46/5081) |
How easy is it to get off our fossil fuel habit? Could Britain live on its own renewable energy? How does our current energy consumption compare with our sustainable energy options? Dr Alison Cooke will offer a straight-talking assessment of the engineering challenges involved, and discuss how to make energy plans that add up, based on the IMechE UK Energy Plan which was presented in Copenhagen in September 2009 alongside 9 other countries.
Dr Cooke is a Fellow of The Institution of Mechanical Engineers and Chair of the UK's Future Climate Steering Group, an international project to mobilise engineers from over 10 developed and developing countries.
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| Energy Concentration in Composite Quantum Systems |
| Dr Almut Beige |
University of Leeds |
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14:30, Friday 12 March 2010 | | Physics Seminar Room (Building 46/5081) |
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The spontaneous emission of photons from optical cavities and from trapped atoms has been studied extensively in the framework of quantum optics. Theoretical predictions based on the rotating wave approximation (RWA) are in general in very good agreement with experimental findings. However, current experiments aim at combining better and better cavities with large numbers of tightly confined atoms. Here we predict an energy concentrating mechanism in the behavior of such a composite quantum system which cannot be described by the RWA. Its result is the continuous leakage of photons through the cavity mirrors, even in the absence of external driving. We conclude with a discussion of the predicted phenomenon in the context of thermodynamics.
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| Laser-Driven Plasma Accelerators |
| Prof Simon Hooker |
University of Oxford |
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14:30, Friday 5 March 2010 | | Physics Seminar Room (Building 46/5081) |
Electrons are pushed away from the front and back of a high-intensity laser pulse as it propagates through a plasma, leading to the formation of a plasma wave which trails the laser pulse. The longitudinal electric field within this wave can be as high as 100 GV/m – more than three orders of magnitude larger than that found in the RF accelerators used at synchrotron and particle accelerator facilities around the world. Laser-driven plasma accelerators are therefore able to accelerate particles to high energies in a fraction of the length required with conventional technology, and in the longer term may offer a way to reach energies beyond those possible with current technology.
Prof Hooker will describe the operation of laser-driven plasma accelerators and discuss the factors which limit the beam energy that they can reach. He will present the results of several experiments, including recent experiments with the Astra-Gemini laser, in which electron beams were generated with energies up to 1 GeV. He will also discuss the application of laser-driven plasma accelerators to the generation of tunable femtosecond-duration x-ray pulses, as well as their potential for reaching energies significantly beyond the GeV range.
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| Gold Nanoparticles, Peptides and Cells: the dynamic picture |
| Dr Raphael Levy |
University of Liverpool |
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14:30, Friday 26 February 2010 | | Physics Seminar Room (Building 46/5081) |
The dynamic interactions and fate of nanomaterials in contact with living systems is thought to be controlled by the structure and chemical properties of its interface. In most cases, the interface is formed by a layer of organic molecules (polymers, proteins or small molecules). This layer is itself dynamic and can evolve due to ligand exchange, enzyme activity and non-specific binding. The layer encodes the specific recognition properties of the particle and also often carries active moieties. It is therefore critical for the progress of the field that the chemical integrity of the layer and the fate of the core materials can be followed independently in real time.
Using a combination of photothermal (imaging of the core material) and fluorescence (imaging of the organic layer) the Liverpool group has shown that peptides and proteins attached to nanoparticles are degraded by the enzyme Cathepsin L upon cell entry. This process is generic: Cathepsin L is ubiquitous and is able to cut a third of the proteome. Such potential degradation has to be taken into account in the design of future bioconjugated nanomaterials.
The degradation mentioned above occurs in the endosomal/lysosomal compartments of the cell. Finding intracellular delivery strategies which reach the cytosol and bypass these compartments is of primary importance for applications of nanomaterials in imaging and nanomedicine. Dr Levy will present a range of approaches currently under investigation in our lab, including the use of targeting peptides and permeabilizing toxins.
Another major challenge in the field is the structural characterization of nanomaterials. This challenge is similar to the one faced by biologists in the early days of structural biology. Dr Levy will report on recent progress on the structural characterization of peptide-capped nanoparticles.
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| Quantum-Opto-Mechanics: quantum-optical control of nano- and micro-mechanical systems |
| Prof Markus Aspelmeyer |
University of Vienna |
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14:30, Friday 19 February 2010 | | Physics Seminar Room (Building 46/5081) |
Nano- and micromechanical resonators are about to become a new paradigm system for quantum science. They combine features that allow unique approaches in both quantum foundations and quantum applications. For example, their flexibility to couple to a variety of physical systems (photons, electrons, atoms etc.) together with their on-chip integrability promises novel transducer schemes for quantum information processing. At the same time, their mass and size allows access to a hitherto untested parameter regime of macroscopic quantum physics such as quantum superposition states involving objects that are visible to the bare eye.
Quantum optics provides a well-developed toolbox to enter and control the quantum regime of mechanical systems. Prof Aspelmeyer will briefly highlight the recent developments of the field and report the current status in his Vienna experiments on laser cooling micromechanical resonators towards their quantum ground state and on strong optomechanical coupling to achieve coherent quantum control. He will also discuss recent progress towards generating optomechanical quantum entanglement, which is at the heart of Schrödinger's cat paradox.
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| Climate Change and Sustainable Energy |
| Dr Hugh Hunt |
University of Cambridge |
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14:30, Friday 5 February 2010 | | Physics Seminar Room (Building 46/5081) |
Is climate change for real? If so, what can we do about it? What is my own carbon footprint? What can I do make a difference? These are the sorts of questions that are addressed in this talk. To answer them we need to do "sums" - just simple addition and multiplication is enough. We must reject solutions that don't "add up" and we mustn't rule out possible solutions purely on emotive grounds. Most people take sides before they've looked at the sums. Our future is in the balance and we're in danger of making the wrong choices.
This talk will draw on material from David MacKay's excellent book "Sustainable Energy Without the Hot Air".
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| Rydberg Aggregates: interactions inan ultracold gas of Rydberg atoms |
| Prof Matthias Weidemüller |
University of Heidelberg |
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14:30, Friday 29 January 2010 | | Physics Seminar Room (Building 46/5081) |
Due to the long-range character of the interaction between highly excited atoms, the dynamics of an ultracold gas of Rydberg atoms is entirely determined by van-der-Waals and dipole-dipole interactions. One outstanding property is the tunability of the strength and the character of the interactions with static electric fields. This allows one to explore the transition from a weakly coupled two-body system to a strongly coupled many-body system. The long-range interaction leads to many-body entanglement and has possible applications in quantum computing. In this talk, Prof Weidemüller will first give a general introduction into the field of Rydberg gases with special emphasis on our recent experiments.
In recent experiments, the Heidelberg group has studied coherent phenomena in an ultracold gas of Rydberg atoms under the influence of dipolar interactions. The Rydberg gas is formed in in a magneto-optical trap via cw two-photon excitation of Rb atoms into states with principal quantum number 30 to 100 using cw lasers at 780 nm and 480 nm. Recent results include coherent Rabi oscillations between ground and Rydberg states and the observation of the dipole blockade in a mesoscopic sample, stimulated rapid adiabatic passage with 90%transfer efficiency into Rydberg states, and studies of the many-body character of resonant energy transfer processes. These experiments reveal the role of interaction-induced mechanical forces as well as the influence of black-body radiation on the many-particle motional dynamics of the system. The latest experiments have revealed the antiblockade of excitation, as the antipode of the dipole blockade, and have explored coherent population trapping under the influence of long-range van-der-Waals forces.
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| The Silent Flight of the Owl (and applications to the design of future quiet commercial aircraft) |
| Prof Geoffrey Lilley OBE |
University of Southampton |
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14:30, Friday 22 January 2010 | | Physics Seminar Room (Building 46/5081) |
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The Owl is the only vehicle that flies silently. It is thought from the fossil record that the owl achieved this some 20 million years ago, and accounts for its survival In this talk we will discuss the details of the owl's hushkit which involves both the aerodynamics and the aeroacoustics as well as the flight performance of the owl. The differences of the owl's feathers from most other birds have been studied by ornithologists for many years but it is only relatively recently that we have measurements and thus discovered a physical understanding of the mechanism involved in achieving silent flight. We conclude the lecture by exploring how we might use Owl Technolgy in the design of future Quiet Commercial Aircraft to almost reduce noise to the ambient level on the take-off and approach to landing when flying over residential areas near airports.
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| Cochlear Implants: signal engineering for profound deafness |
| Dr Carl Verschuur |
University of Southampton |
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14:30, Friday 8 January 2010 | | Physics Seminar Room (Building 46/5081) |
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Cochlear implants are surgically implanted devices that provide a sensation of hearing, along with some ability to perceive speech, to individuals with severe to profound deafness who cannot benefit from acoustic hearing aids. This talk will provide an overview of what cochlear implants are, how they work, what benefits they provide for recipients, and what technical and scientific challenges lie ahead in the treatment of profound deafness with implantable devices.
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| LUCID: Putting a CERN Detector in Space and in Schools |
| Ms Becky Parker MBE |
Langton Star Centre, and
Simon Langton Grammar School for Boys |
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14:30, Friday 11 December 2009 | | Physics Seminar Room (Building 46/5081) |
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The Langton Star Centre at Simon Langton Grammar School for Boys is working closely with CERN and Surrey Satellite Technology Limited to put a new design of cosmic ray detector into space. This will be linked to an array of school detectors with the aim of giving students the opportunity to be involved in real physics research when they are at school. The wealth of data expected will make use of the facilities of the GridPP. We are hoping that working in this way with CERN technology will enthuse students and encourage them to consider taking physics and engineering further.
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| The Electron's Electric Dipole Moment |
| Dr Jony Hudson |
Imperial College, London |
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14:30, Friday 4 December 2009 | | Physics Seminar Room (Building 46/5081) |
Some theories beyond the standard model predict that, when examined with sufficiently high resolution, the electron will no longer appear to be point-like and may instead show some finite structure. This should be apparent as an electric dipole moment parallel to the electron's spin. Because spin is inverted if time is reversed, the existence of an electric dipole moment would violate time-reversal and parity symmetries: central assumptions of the standard model.
Any electron electric dipole moment will be manifest as small shifts in atomic spectra, and such effects have long been predicted to be greatly enhanced when the atoms are within polar molecules. The Imperial College group has therefore been running a long campaign to measure, with ever increasing precision, the electron's electric dipole moment in the spectra of ytterbium fluoride. Based upon matter-wave interferometry for the highest resolution, these elegant experiments also provide a fascinating example of the challenges of eliminating systematic errors in the measurement of fundamental physical properties.
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| Current and Future Power Generation |
| Mr Jonathan May |
e.on UK |
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14:30, Friday 27 November 2009 | | Physics Seminar Room (Building 46/5081) |
The critical questions of how, where and from what we generate power, and how it is distributed, depend upon environmental sustainability, geopolitics, technological developments, and the availability and geographical distribution of energy sources. Our current pattern of coal, gas, nuclear, hydroelectric and wind-based power stations will have to change substantially if we are to meet future demand in a safe, secure and sustainable fashion.
This talk will describe some of the methods by which we generate and distribute power at present, and their suitability for meeting future needs. It will then examine a range of technologies for future power generation, and some of the challenges that they present.
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| Creating and Manipulating Cold Molecules with Intense Optical Fields |
| Prof Peter Barker |
University College, London |
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14:30, Friday 20 November 2009 | | Physics Seminar Room (Building 46/5081) |
The creation of cold molecular gases and the precise control of the centre-of-mass motion of molecules by external fields have become an important new field in molecular and ultra-cold physics and in chemistry. The long residence times of trapped cold molecular gases coupled, with their reduced momentum spread, allows high resolution spectroscopy and the study of molecular interactions that are normally masked by thermal averaging at temperatures above 1 K. An important example is cold, trapped dipolar gases, which offers a route to the study of many body condensed matter physics and quantum information processing in a well-controlled system that can be tailored using external fields.
In this talk, Prof Barker will review the development of techniques to slow and manipulate cold molecules focusing in particular on the optical Stark deceleration technique which uses the optical dipole force. He will then describe more recent work on how this force can be tailored using laser-induced alignment in strong optical fields. Finally, he will report on progress in his laboratory towards sympathetically cooling these molecules with ultra cold rare gas atoms with the aim of reaching the microKelvin temperature regime for a large range of molecular species.
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| Medical Imaging and Applications in Drug Discovery |
| Dr Will Hallett |
GSK Clinical Imaging Centre, Imperial College |
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14:30, Friday 13 November 2009 | | Physics Seminar Room (Building 46/5081) |
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Physics principles and techniques lie behind the many and astonishing methods of medical imaging, from nuclear magnetic resonance (MRI), positron emission (PET) and X-ray computed tomography (CT) to ultrasound, confocal microscopy and optical coherence tomography. Already indispensable in clinical use, these techniques are now also being applied to molecular imaging for drug discovery and development. Dr Hallett's talk will begin by outlining the basic physics of medical imaging techniques, before discussing some of their more important and intriguing applications.
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| Superposition of Quantum Operators and a Test of the Bosonic Commutation Relation |
| Prof Myungshik Kim |
Queen's University, Belfast |
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14:30, Friday 6 November 2009 | | Physics Seminar Room (Building 46/5081) |
One of the most striking formulas we learn during the undergraduate quantum mechanics course is the commutation relation, [a, a+] = 1. For a light field, this means that photon annihilation after creation is different from photon creation after annihilation and the difference is equal to the unity. The non-commutativity is closely related to the uncertainty principle in quantum mechanics; the precise measurement of two non-commutative observables simultaneously is impossible. Even though the bosonic commutation relation is taught in every quantum mechanics course, the direct and 'exact' proof seemed to be experimentally unreachable. In this talk, the verification of the bosonic commutation relation is discussed using single photon interference.
Prof Kim will demonstrate a scheme based on single-photon interference for transferring the microscopic quantum behaviour to macroscopic classical objects (as in Schrödinger's cat paradox) by realising arbitrary superpositions of distinct quantum operations. Applying them to a classical light field the commutation relation to be verified directly. The Belfast group's results may be interesting because, in addition to clear demonstration of the fundamental textbook concept in quantum mechanics, the possibility of implementing general operator superpositions is an alternative promising tool to control and engineer quantum information for future technologies.
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| Engineering Atom Chips |
| Prof Michael Kraft |
University of Southampton |
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14:30, Friday 23 October 2009 | | Physics Seminar Room (Building 46/5081) |
Atom Chips are a new and exciting technology that enable the manipulation of atoms close to a chip surface. These chips combine cold atom physics with MEMS microfabrication techniques to create electric, magnetic and optical fields to trap and manipulate ultra-cold atom clouds.
The microfabricated chips realise optical cavities, electrostatic actuators and current carrying wires to set up magnetic trapping fields. Besides fundamental physics experiments, there are a range of novel devices and sensors on the horizon that use this technology. In prototype devices, atom chips are already being used to make Bose Einstein condensates for applications including atomic clocks on a chip, atom interferometry, and quantum information processing.
The talk will describe micro-fabrication technologies that can realize the required building blocks and components to realize such atom chips. It will mainly focus on the microfabrication and design engineering aspects of these chips, as they almost entirely rely on non-standard fabrication techniques, which need to be specially developed for these chips. Additionally, they combine a range of different physical domains such as optical, magnetic and electrostatics, which makes their design and realization challenging.
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| The Hunt for Gravitational Waves |
| Dr Ed Daw |
University of Sheffield |
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14:30, Friday 16 October 2009 | | Physics Seminar Room (Building 46/5081) |
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The search for gravitational waves using ground based laser interferometers is now well underway, and becoming progressively more sensitive through an ongoing programme of instrument upgrades. In this talk, Dr Daw will discuss gravitational waves and the physical principles of interferometric detectors such as LIGO, Virgo and GEO600, before exploring the intriguing possibility of detection of a counterpart to a putative gravitational wave transient either in the optical or the radio. Such a dual-channel detection would provide compelling evidence for first direct detection of gravitational waves, as well as providing a wealth of information on the physics of compact gravitational wave sources.
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| Light on the Nanoscale: energy harvesting and the optical assembly of particles |
| Prof David Andrews |
University of East Anglia |
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14:30, Friday 9 October 2009 | | Physics Seminar Room (Building 46/5081) |
Recent progress in the theory of photon interactions has revealed a catalogue of new mechanisms engaging the nanoscale propagation of light. At routinely achievable levels of laser intensity, non-resonant light can operate on pairs of particles can produce movements of energy and matter without itself suffering any change. Prof Andrews will begin by examining how non-resonant light can engage with, and modify van der Waals forces. The principles are readily understood from a quantum electrodynamical perspective, and a variety of applications is emerging. Some applications such as optical binding, already extensively demonstrated in experiment, offer a degree of control well beyond the capacity of simple optical tweezers. The phenomenon allows the ordering and patterning of particles in arrays and rings, and distinctive torques can be exerted. Other effects that originate from the same fundamental process extend from a novel optomechanical response (optical electrostriction) in transparent solids to an optical method of collapsing nanoparticle assemblies.
A further theme of the presentation is the more recent discovery of a means by which non-resonant laser light can promote, inhibit or switch the transfer of electronic energy between molecules. It transpires that precisely the same photonic coupling mechanism is again involved. Interest initially focused on laser-assisted modifications to the process of fluorescence resonance energy transfer (FRET); now attention is being given to switching applications. A variety of possibilities exist to effectively channel excitation between paired components; array implementations offer interesting opportunities for optical interconnect technology.
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| The Lonely World of the Cold, Trapped Ion |
| Prof Richard Thompson |
Imperial College, London |
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14:30, Friday 19 June 2009 | | Physics Seminar Room (Building 46/5081) |
Single ions, trapped electrostatically in ultrahigh vacuum and slowed optically by exploiting the Doppler effect, can be held essentially stationary and isolated from the nearest matter many millimetres away. Narrow transitions in atomic ions are thus amongst the most ideal quantum systems that we know, and are therefore the favourite candidates for future frequency standards and metrology. When two such ions are held in the same trap, their interactions can be controlled with exquisite detail and precision, making them suitable for use as the processor of a quantum computer, with single ions providing the quantum memory.
Prof Thompson will describe recent work at Imperial with trapped and laser-cooled calcium ions. In one experiment the limitations to laser cooling have been overcome in the so-called Penning trap so that individual ions can be imaged and the configuration that two ions take in the trap can be manipulated. In another experiment small amounts of mixing between different levels of a configuration, induced by a magnetic field, have been demonstrated to lead to easily-observed effects in the fluorescence from a single ion. Prof Thompson will finish by discussing a proposal for the observation of a quantum phase transition in a string of trapped ions.
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| Interfacing Cells with Colloidal Nanoparticles |
| Prof Wolfgang Parak |
University of Marburg |
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14:30, Friday 12 June 2009 | | Physics Seminar Room (Building 46/5081) |
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Colloidal nanoparticles may be grown to have a variety of different functionalities, such as being fluorescent or magnetic. By using biological molecules to link them, particles of different functionalities can be integrated to form composite materials on the nm-scale. Applications of such particles in life science will be discussed.
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| Discoveries That Changed the World: 1932-1942 - James Chadwick & Lise Meitner |
| Dr Gerry Lander |
Institute for Transuranium Elements, Karlsruhe & ILL, Grenoble |
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14:30, Friday 5 June 2009 | | Physics Seminar Room (Building 46/5081) |
From the discovery of the neutron (1932) to the first demonstration of controlled fission (1942) was just ten years; a period that took physics from an occupation of a small number of eccentric gentlemen and (even fewer) ladies to something of concern to, and funding decisions of, Governments all over the world. The shadows of those tumultuous years are still with us, for better or worse.
This talk will recount those ten years through the lives of James Chadwick (1891-1974) and Lise Meitner (1878-1968), contemporaries who played pivotal roles in the events, even though, partly because of their retiring personalities, they are often overshadowed by "larger" figures.
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| Coherent X-Ray Imaging with X-Ray Free Electron Lasers |
| Prof Henry Chapman |
DESY & University of Hamburg |
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14:30, Friday 29 May 2009 | | Physics Seminar Room (Building 46/5081) |
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The ultrafast pulses from future X-ray free-electron lasers may enable imaging of non-periodic objects at near-atomic resolution. These objects could include single macromolecules, protein complexes, or virus particles, and the method will be particularly valuable to determine the structures of proteins that cannot be crystallized. The specimen would be completely destroyed by the pulse, but that destruction will only happen after the termination of the pulse. To address the many challenges that we face in attempting molecular diffraction, Prof Chapman and his colleagues have been developing experimental methods at the FLASH free-electron laser at DESY in Hamburg: images have been reconstructed from single-pulse ultrafast diffraction patterns, and quantitative measurements have been performed of the explosion of test particles in the focused FEL pulse. No motion is observed during the pulse and the evolution of the explosion can be followed with a novel holographic time-resolved technique. These results confirm the basic principles of flash imaging and lend great confidence to achieving molecular imaging at future short-wavelength X-ray FELs.
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| Restoration of Faded Photographic Slides |
| Dr Geoff Daniell |
University of Southampton |
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14:30, Friday 22 May 2009 | | Physics Seminar Room (Building 46/5081) |
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One of Geoff's retirement projects has been the digitization of his old holiday slides, many of which have unfortunately deteriorated seriously with age. After an entire wet Sunday afternoon moving sliders on digital photo processing software, but discovering that he could not do better than the 'auto' button, Geoff decided that he ought to be able to improve upon the results by thinking about the physics of the photographic process. This talk will describe the mechanisms of old-fashioned photography, conjecture on why photographs have deteriorated, describe the algorithms he has developed, and show some results.
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| Super-Hydrophobic Surfaces |
| Dr Steven Bell |
Queen's University, Belfast |
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14:30, Friday 15 May 2009 | | Physics Seminar Room (Building 46/5081) |
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In the first decade following publication of Neinhuis and Barthlott's studies of water repellent, self-cleaning plants there has been a huge expansion in research which attempts to mimic the exceptional properties of natural systems, such as the lotus plant. This talk will cover current progress in preparation of artificial superhydrophobic materials, including our work on electrolessly deposited metal coatings (see the metal pond skater with superhydrophobic legs shown here) and will include some practical demonstrations of the effect of adding superhydrophobic coatings to materials. It will also include some recent examples of superhydrophobic platforms for surface enhanced Raman spectroscopy and speculation on the potential applications for the technology.
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| Green Aviation - Fact or Fiction? |
| Dr Kenji Takeda |
University of Southampton |
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14:30, Friday 24 April 2009 | | Physics Seminar Room (Building 46/5081) |
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Air travel is cited as being the fastest growing source of climate changing gases and heavily criticised for being a major culprit of global warming. This is despite air travel only contributing around 3%of global carbon dioxide emissions, and UK domestic air travel contributing less than 0.5%of UK carbon dioxide output. In this talk, Dr Takeda will explore the scientific, technical and social issues around air travel and climate change, and try to present a balanced view of where we are heading in the future. He will attempt to outline the steps required to ensure that aviation meets its environmental obligations to society in the 21st century.
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| Greenwich Mean Time |
| Mr David Rooney |
Curator of Timekeeping, Royal Observatory, Greenwich |
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14:30, Friday 20 March 2009 | | Physics Seminar Room (Building 46/5081) |
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Precise maritime navigation, in the days before radio, required precise timekeeping, and ships leaving the Port of London would set their clocks according to the timepieces and signals of the Greenwich Royal Observatory. Greenwich Mean Time - derived using precise chronometers from careful observations of solar transits - became a global maritime reference; when the railways required national coordination, it was adopted as the British civil standard, and in 1884 the Greenwich meridian officially became the international reference for navigation and timekeeping. Today's atom-based UTC is adjusted, by the addition or subtraction of leap seconds, to remain within a second of GMT. David Rooney - a physicist turned historian of technology - will outline the history of Greenwich Mean Time and some of its many quirky stories, including that of the Greenwich Time Lady whose family continued until 1940 to distribute the time to tradesmen by carrying a pocket watch around London.
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| Liquid Crystals for Electro-Optics |
| Dr Sally Day |
University College, London |
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14:30, Friday 13 March 2009 | | Physics Seminar Room (Building 46/5081) |
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Liquid crystals re-orient under the influence of a low voltage to give a very large change in the effective birefringence. Liquid Crystal Displays use this effect to change the polarisation of light, hence changing the intensity of transmitted light through polarisers. The change in birefringence can be used for other applications and this talk will describe some of these; from variable focal length lenses, tuneable Fabry-Perot filters, phase modulation for diffraction and applications in microwave devices. In addition, new displays, such as bistable displays and an autostereoscopic display will be discussed.
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| Quantum Optics with Quantum Dot Spins |
| Dr Mete Atatüre |
University of Cambridge |
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14:30, Friday 27 February 2009 | | Physics Seminar Room (Building 46/5081) |
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Self-assembled semiconductor quantum dots have atom-like properties such as discrete energy levels coupled by optical transitions, and their coherence properties can be revealed in quantum-optics experiments. Further, these transitions are governed by spin-dependent optical selection rules. This opens a channel to control and detect a single spin in a quantum dot via lasers. However, QDs can also interact strongly with a spin (nuclei) and/or a charge (electrons) reservoir of the solid-state environment leading to a rich source of interaction mechanisms. Consequently, identifying the regimes of these mechanisms is crucial for achieving a level of control in solid-state-based systems similar to that of atoms. Dr Atatüre will provide a highlight of recent progress on all-optical control of single and coupled quantum dot spins along with the current research directions in coherent light-matter interactions.
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| Controllable Single Photon Sources and Strong Coupling |
| Prof Robert Taylor |
University of Oxford |
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14:30, Friday 20 February 2009 | | Physics Seminar Room (Building 46/5081) |
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Much effort has been expended over the past few years in trying to develop controllable and triggerable single photon sources based on semiconductor emitters. Prof Taylor will discuss recent developments in the field and focus on what happens when quantum dots are coupled to external cavities to try and produce strong coupling in the solid state.
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| Synthesis, Properties and Assembly of Complex Nanocrystal Structures |
| Dr Liberato Manna |
University of Lecce |
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14:30, Friday 13 February 2009 | | Physics Seminar Room (Building 46/5081) |
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Current efforts and success of nanoscale science and technology are related to the fabrication of functional materials and devices in which the individual units and their spatial arrangement are engineered down to the nanometer level. One promising way of achieving this goal is by assembling of colloidal inorganic nanocrystals as the novel building blocks of matter. This trend has been stimulated by significant advancement in the wet-chemical syntheses of robust and easily processable nanocrystals in a wide range of sizes and shapes. The increase in the degree of structural complexity of solution-grown nanostructures appears to be one of the natural directions towards which nanoscience will increasingly orient. Recently, several groups have indeed devised innovative syntheses of nanocrystals through which they have been able to group inorganic materials with different properties in the same particle. These approaches are paving the way to the development of nanosized objects able to perform multiple technological tasks. This talk will review the recent advances in the synthesis of colloidal nanocrystals, with emphasis on the strategies developed at NNL for the fabrication of colloidal nano-heterostructures, as well as on their properties and their assembly.
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| Quasicrystals: from Fibonacci to the Frying Pan |
| Prof Ronan McGrath |
University of Liverpool |
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14:30, Friday 6 February 2009 | | Physics Seminar Room (Building 46/5081) |
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Do structural symmetry and periodicity matter when we try to understand the physical properties of ordered materials? Quasicrystals are intermetallic alloys which have long-range order without periodicity and hence display unusual rotational symmetries. Their structures are described by models related to Penrose tilings and Fibonacci numbers. This talk will introduce these materials and discuss using their surfaces as templates for building novel nanostructures and thin films. One of the main goals of the research programme is to clarify the physical consequences of classically forbidden structural symmetries and aperiodicity. Prof. McGrath will also mention potential applications arising from their unusual physical properties.
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| Molecular Properties Measured by Near-Field Interferometry |
| Dr Hendrik Ulbricht |
University of Southampton |
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14:30, Friday 30 January 2009 | | Physics Seminar Room (Building 46/5081) |
Matter wave interferometry experiments with very massive molecules has the potential to test fundamental physics as the quantum to classical transition. But the very same experimental setup can also be used to investigate molecular properties as for instance static and dynamic polarizabilities, electric dipole moments, absoprtion cross sections and van der Waals interaction parameter from collision cross sections to an high degree of precision - as well as for molecular and nanoparticle beam sorting.
Dr Ulbricht will report on the recent status of molecule interfernce with Talbot-Lau and Kapitz-Dirac-Talbot-Lau interferometers with organic molecules of masses of up to 2500 amu and then extend on the various metrology opportunities. He will also discuss particle beam manipulation techniques for the slowing and cooling of massive molecules, which are central to both the probing of quantum limits and molecule metrology.
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| On Wanting To Be Free: music meets technology |
| Mr Paul Jessop |
RIAA |
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14:30, Friday 23 January 2009 | | Physics Seminar Room (Building 46/5081) |
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Music remains as popular as at any time in human history, but the way we get access to it and the way we consume it would be incomprehensible to our ancestors. Changes in music use have been enabled by some key technologies and the changes continue. This talk will review these technologies – such as audio compression, watermarking, fingerprinting and forensics. It will also look at some of the resulting issues in the music ecosystem where technology, policy, regulation, politics, creativity, ethics and consumer behaviour are sometimes pulling in orthogonal directions.
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| Taming Molecular Beams |
| Prof Gerard Meijer |
Fritz-Haber Institute, MPI Berlin |
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14:30, Friday 16 January 2009 | | Physics Seminar Room (Building 46/5081) |
Full control of both the internal and external degrees of freedom of molecules has been an important goal in molecular physics for many decades. Prof Meijer will describe the experimental approach developed by his group to produce samples of trapped neutral molecules. Based upon arrays of time-varying, inhomogeneous electric fields which reduce in a stepwise fashion the forward velocity of molecules in a beam, this so-called 'Stark decelerator' can transfer the high phase-space density present in the moving frame of a pulsed molecular beam to a reference frame at any desired velocity, with narrow velocity distributions that correspond to sub-mK longitudinal temperatures.
These decelerated beams offer new possibilities for collision studies, and enable spectroscopic studies with improved spectral resolution; first proof-of-principle experiments have been performed. They have also been used to load ND3 molecules and OH radicals into an electrostatic trap at a density of 107 mol cm-3 and at temperatures of around 50 mK. Optical pumping of trapped neutral molecules due to blackbody radiation has been investigated, and trapping of molecules in vibrationally or electronically excited metastable states has been used to directly measure their radiative lifetimes. Ground-state molecules have been trapped in AC electric field traps, decelerated molecular beams have been injected in a prototype molecular synchrotron, and, using micro-structured electrode arrays, a "decelerator on a chip" has been constructed and tested.
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| Rainbows, Coronas and Glories |
| Mr Philip Laven |
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14:30, Friday 9 January 2009 | | Physics Seminar Room (Building 46/5081) |
Rainbows, coronas and glories are examples of atmospheric optical phenomena caused by the scattering of sunlight from spherical drops of water. Eminent scientists (such as Descartes, Newton, Young, Airy and others) offered various explanations for the formation of rainbows - and thus made major contributions to our understanding of the nature of light.
Given the availability since 1908 of Mie's rigorous solution for scattering of light by homogeneous spherical particles, it might be assumed that everything is now known about the rainbow, corona and glory. In fact, atmospheric optics has long been a neglected topic for scientific studies. It is only in recent years that rapid advances in computing power have allowed Mie's solution to be used to investigate these phenomena - and to produce full-colour simulations.
The physical processes resulting in the formation of rainbows and coronas are well understood, but most explanations of the glory involve lots of "scientific arm-waving". Using the results of detailed calculations and simulations, this talk will aim to provide some insight into the physics of rainbows, coronas and glories - and to encourage the audience to enjoy the beauty of these phenomena.
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| Forecasting the British Weather |
| Ms Kirsty McCabe |
Met. Office & BBC Weather Centre |
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14:30, Friday 12 December 2008 | | Physics Seminar Room (Building 46/5081) |
While the weather provides the British with both a constant topic of discussion and a source of fascination, it presents the forecaster with endless challenges. The British Isles are influenced by polar and tropical air masses; they frequently find themselves beneath the jetstream, and are subject to untempered Atlantic weather about which we have only limited data. Few other locations see such notable changes in weather from place to place and day to day. It was to study and forecast this weather that a meteorological service was established by Admiral Fitzroy in 1854, and for 150 years the Met. Office has provided warnings of extreme weather to our mariners, armed services and general public.
Today's talk will give a behind the scenes look at weather forecasting, from understanding the atmosphere to numerical weather prediction, including an introduction to air masses, cloud formation and cloud classification, cases of wild weather - and the challenge of presenting the public forecast itself.
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| Hybrid Inorganic/Organic Photonics |
| Dr Stephanie Cheylan |
ICFO, Barcelona |
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14:30, Friday 5 December 2008 | | Physics Seminar Room (Building 46/5081) |
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Conjugated polymers have become attractive for a range of device applications such as light-emitting diodes, photo-voltaic cells and transistors. While there is true value in making all-plastic devices, some devices such as the diode laser still require an inorganic component to be feasible. In this talk, Dr Cheylan will outline some of the attractive properties of such hybrid devices.
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| Exploring Extrasolar Worlds: from gas-giants to terrestrial planets |
| Dr Giovanna Tinetti |
University College, London |
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14:30, Friday 28 November 2008 | | Physics Seminar Room (Building 46/5081) |
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Since the presence of a planet orbiting the star Gamma Cephei was first established in the early 1990s, over 300 further extrasolar planets have been identified, using a wide range of observational techniques from astrometry and radial velocity measurement to gravitational microlensing and transit observations. The Hubble Space Telescope has allowed some remarkable advances, including the direct imaging this month of three planets around the star Fomalhaut in the constellation Piscis Austrinus. Spectroscopic measurements using the Hubble telescope have also allowed analysis of the atmospheres of these remote worlds, with the identification of water and methane around the hot, Jupiter-type planet HD 189733b, 63 light-years away in the constellation Vulpecula. Such measurements herald future analysis of cooler, more Earth-like and potentially habitable planets to reveal information about the atmospheric temperature, pressure, winds, clouds and chemistry of extrasolar planets where life could potentially exist.
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| Atomic Frequency Metrology |
| Dr Anne Curtis |
National Physical Laboratory |
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14:30, Friday 21 November 2008 | | Physics Seminar Room (Building 46/5081) |
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The precise measurement of time and frequency - the subject of the 2005 Nobel Prize in Physics - has major applications from fundamental science and the quest for physics beyond the standard model, to technologies such as ultra-precise satellite-based navigation. Dr Curtis will begin with a basic introduction to frequency metrology and an overview of the state-of-the-art in atom-based frequency metrology, including clocks based upon Cs fountains, single ions and neutral atom lattices. She will then discuss some fundamental physics experiments and more practical, real-world applications that depend upon such timepieces.
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| Spin Noise Spectroscopy |
| Prof Michael Oestreich |
Leibniz Universität, Hannover |
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14:30, Friday 14 November 2008 | | Physics Seminar Room (Building 46/5081) |
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Electron, hole, and nuclear spins in semiconductors offer additional degrees of freedom for a new kind of information processing and optoelectronic devices. In this talk, Prof Oestreich will first discuss the exciting prospects and challenges of semiconductor spintronics and afterwards describe how to extract the spin dynamics and spin relaxation in semiconductors solely by measuring noise. The experimental technique is called spin noise spectroscopy and allows non-demolition measurements of spin systems in thermal equilibrium with astonishing sensitivity.
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| Attosecond Angular Streaking and Sub-100as Tunnelling Time Dynamics |
| Prof Ursula Keller |
ETH Zurich |
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14:30, Friday 7 November 2008 | | Physics Seminar Room (Building 46/5081) |
Prof Keller's group has demonstrated attosecond angular streaking, a new technique to achieve attosecond time resolution using close to circularly polarized, intense pulses. The rotating electric field vector of the slightly elliptically polarized pulse is used to deflect photo-ionized electrons in the radial spatial direction, such that - like the minute hand of a clock - the instant of ionization is mapped to the final angle of the momentum vector in the polarization plane. Here, this ‘atto-clock' makes one complete turn of the electric field each 2.4 fs. It requires pulse durations in the two optical cycle regime and carrier envelope offset phase (CEP) control, and can be used with or without any attosecond XUV pulses. The Zurich group has resolved subcycle dynamics in tunneling ionization by the streaking field alone, and demonstrated a temporal localization accuracy of 24 as rms and an estimated resolution of ?200 as.
The demonstrated accuracy raises the possibility of examining one of the fundamental aspects of quantum physics: the process by which an electron tunnels through an energetically forbidden region. Since the early days it has been debated whether tunnelling takes a real time or is instantaneous. Prof Keller will discuss the demonstration of intensity-independent "instantaneous" ionization with an upper limit of ?30 attoseconds over a Keldysh parameter variation of 1.45 to 1.17.
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| Cody and Roe: Two Remarkable Men |
| Mr Philip Jarrett |
Aeroplane Monthly |
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14:30, Friday 31 October 2008 | | Physics Seminar Room (Building 46/5081) |
On 16th October 1908, 'Colonel' Samuel Franklin Cody made the first powered, sustained and controlled flight in Britain, just a few miles from here at the Army Balloon Factory in Farnborough. A few months later, just over the county border at the Brooklands motor-racing track in Surrey, Alliott Verdon Roe was testing his first full-size aircraft which, after tentative hops in July 1908, first flew properly the following year. Cody's exploits led to the establishment of Farnborough as Britain's leading centre for aircraft research and development, while Roe went on to found the world-famous AVRO aircraft manufacturing company, and subsequently Saunders-Roe Aviation on the Isle of Wight.
The two men were very different characters - Cody a flamboyant extrovert, Roe much more reserved. But both were remarkable individuals and equally great pioneers of British aviation. This lecture will highlight their achievements, describe their respective approaches to the problems of powered flight and discuss how they went on to develop and fly progressively improved versions of theiraeroplanes over the following few years.
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| A Random Walk Approach to Quantum Computing |
| Dr Viv Kendon |
University of Leeds |
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14:30, Friday 24 October 2008 | | Physics Seminar Room (Building 46/5081) |
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In a quantum world - the regime in which quantum effects are not disguised by thermal motion and dissipation - common, classical phenomena can assume rather different characteristics. Beginning with a gentle introduction to quantum computing, Dr Kendon will explain the mechanisms and characteristics of the quantum versions of random walks. Intriguingly, quantum walks can actually be improved in some cases by adding a little noise instead of striving to keep them perfect.
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| Closing In on Ultra-High Energy Neutrinos |
| Dr Amy Connolly |
University College, London |
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14:30, Friday 17 October 2008 | | Physics Seminar Room (Building 46/5081) |
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Dr Connolly will describe current and future experiments that seek ultra-high energy cosmic neutrinos, which are so evasive they require detection volumes beyond 100's of km3. Volumes of such size are achievable using the radio Cerenkov technique, and Dr Connolly will discuss current and future projects that use this detection method, including the ANITA balloon experiment which just completed its first physics flight in the 2006-2007 Austral summer and whose second flight is scheduled for December this year.
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| Polarised Fermi Gases |
| Dr Carlos Lobo |
Universities of Cambridge & Southampton |
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14:30, Friday 10 October 2008 | | Physics Seminar Room (Building 46/5081) |
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In the past two years various experiments have been carried out at Rice University and MIT on ultracold gases of fermionic atoms where one type of spin component is more abundant than another. These so-called polarised or imbalanced gas experiments may soon answer tantalising questions regarding Fermi superfludity which have been around for over 45 years. Dr Lobo will review the experimental situation and describe how some of the puzzling data can be understood in terms of normal state properties of these strongly interacting systems.
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| String Theory for Heretics |
| Prof Nick Evans |
University of Southampton |
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14:30, Friday 20 June 2008 | | Physics Seminar Room (Building 46/5081) |
(Nick has sadly been too busy to provide an abstract for his talk this Friday, but I think I can remember the gist...)
String - as Raymond Baxter explained so memorably in his classic 1976 Goodies cameo - has a thousand uses: from cartlidge replacements in hospital operations, to a substitute for conventional electric wiring - "safer and cheaper because... it doesn't work". Yet while Baxter was astonished that a mere television studio could be built from string, modern theories suggest that it may hold together the entire universe.
'Most physicists nowadays,' according to a more recent science programme, 'believe in string theory'. Nick's talk is aimed at the rest of us, who have barely a clue what it's all about.
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| Radio Telescopes as Physics Facilities |
| Prof Steve Rawlings |
University of Oxford |
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14:30, Friday 13 June 2008 | | Physics Seminar Room (Building 46/5081) |
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Traditionally radio telescopes have been used by astronomers. The next generation of telescopes will have such new capabilities that they will be capable of performing experiments that impact on issues of fundamental physics: the testing of General Relativity in the strong-field limit; the measurement of neutrino masses; the nature of dark energy etc. Prof Rawlings will review prospects for the future, and specifically the scientific pathway to the Square Kilometre Array (SKA).
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| The Antikythera Mechanism |
| Prof Mike Edmunds |
University of Cardiff |
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14:30, Friday 30 May 2008 | | Physics Seminar Room (Building 46/5081) |
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Over a century ago, sponge divers near the island of Antikythera discovered an ancient device that astonished experts worldwide. Now known to date from the first century B.C., and considered the most sophisticated known mechanism from the ancient world, this fascinating bronze and wooden relic has only recently begun to divulge its intriguing secrets. X-ray and novel computer-aided imaging techniques have allowed an international team of researchers from mathematicians and physicists to astronomers and palaeographers to identify the Antikythera Mechanism as a complex mechanical 'computer', dedicated to astronomical phenomena, to track the cycles of the Solar System. No other mechanism as complex is known until a thousand years later.
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| The Physics of Woodwind Instruments |
| Dr David Sharp |
Open University |
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14:30, Friday 23 May 2008 | | Physics Seminar Room (Building 46/5081) |
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The woodwind family of musical instruments includes, amongst others, the flute, oboe, clarinet, bassoon and saxophone. Through a series of demonstrations and multimedia examples, this talk discusses the physics of the woodwind instruments. In particular, the mechanisms by which the different instruments produce sound are described and the reasons why each woodwind instrument has its own characteristic tone are explained.
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| Nanophotonics and Biochemistry |
| Prof Jochen Feldmann |
Ludwig-Maximilians-Universität, Munich |
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14:30, Friday 16 May 2008 | | Physics Seminar Room (Building 46/5081) |
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Nanoplasmonics offers new tools to analyze or to manipulate biomolecules, whereas the self-recognition capabilities of biomolecules help to assemble hybrid nano-assemblies with unique optical properties and functions. Prof Feldmann will show several examples of how these two fields profit from each other.
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| Attosecond Dynamic Imaging |
| Dr John Tisch |
Imperial College, London |
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14:30, Friday 9 May 2008 | | Physics Seminar Room (Building 46/5081) |
High harmonic generation (HHG) in gases driven by intense, femtosecond laser pulses provides a very promising source of coherent short wavelength radiation in the 5-100nm range. High harmonic radiation is the result of coherent "recollisions" of a laser driven electron wavepacket with its parent ion. A unique feature of this light is its very short pulse nature (down to ~0.1fs = 100 as) and its precise synchronisation with the driving laser pulse. This allows it to be used in pump-probe type studies (typically XUV+IR) to track ultrafast dynamics. A less-well known feature of HHG is that the electron recollision event can be used to image molecular structure and dynamics on the attosecond timescale and sub-Angstrom length scale.
This talk will review the production of HHG light as a coherent source for imaging and discuss some of the exciting developments in recent years on attosecond timescale dynamic measurements.
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| Searches for Extra Dimensions at the LHC |
| Dr Tracey Berry |
Royal Holloway, University of London |
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14:30, Friday 2 May 2008 | | Physics Seminar Room (Building 46/5081) |
The Large Hadron Collider (LHC) at CERN will become the world's largest - and highest energy - particle accelerator when it produces its first beams later this year. As well as finally yielding the elusive Higgs boson, the LHC could produce other novel species, from superpartner particles to tiny black holes.
Dr Berry will summarise the potential of the ATLAS and CMS experiments at the LHC to search for extra-dimensional models, describing their distinctive experimental signatures and the expected discovery limits. She will discuss the reaches expected in different channels and proposals to distinguish these models from other new physics scenarios.
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| Molecular Motors |
| Dr John Sleep |
King's College, London |
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14:30, Friday 25 April 2008 | | Physics Seminar Room (Building 46/5081) |
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Motors convert chemical energy into mechanical work and in the biological realm this process occurs most obviously in muscles through the action of the protein myosin on adenosine triphosphate. In fact most of the 39 distinct myosins in the human genome are responsible for motions within non-muscle cells and they display a wide range of properties. Moreover, there are two other classes of linear motor, kinesins and dyneins, each example of which has a precise function in the body.
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| Bose-Einstein Condensation with Tunable Interactions: from solitons to molecules |
| Dr Simon Cornish |
University of Durham |
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14:30, Friday 14 March 2008 | | Physics Seminar Room (Building 46/5081) |
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The last decade has witnessed an explosion of research in the field of quantum degenerate gases. Experimental activity continues to progress at a remarkable rate as existing techniques are extended and combined in ever richer systems. Recent "hot topics" include the study of Feshbach resonances, the realization of quantum degenerate mixtures and the investigation of quantum degenerate gases in optical lattice potentials. This talk will outline the development and motivation behind two Bose-Einstein condensation experiments at Durham which aim to explore these exciting topics.
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| Nonlinear Dynamics of the Cardiovascular System |
| Prof Peter McClintock |
University of Lancaster |
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14:30, Friday 29 February 2008 | | Physics Seminar Room (Building 46/5081) |
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The cardiovascular system may be considered to comprise many coupled nonlinear oscillators, differing in their physiological origins, whose behaviour can be inferred by applying various techniques of nonlinear, stochastic and fractal analysis. Models thus obtained of the cardiovascular system, and the interaction between the cardiac and respiratory systems, allow the identification of age-related changes, and promise a powerful tool for the solution of a long-standing challenge: the development of new diagnostic techniques based upon non-invasive measurements.
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| Lab-Based Ultrafast Soft X-Rays: the affordable alternative to syncrotrons |
| Dr Sarah Stebbings |
University of Southampton |
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14:30, Friday 22 February 2008 | | Physics Seminar Room (Building 46/5081) |
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The production of coherent, ultrafast x-rays via a process known as high harmonic generation offers many potential applications across a wide range of scientific endeavours. Their wavelengths (e.g. 1 - 40 nm) and sub-femtosecond (i.e. < 10-15 seconds) pulse duration make them ideal for probing the structure of nanoscale objects as well as studying ultrafast electron dynamics in real time, thus opening up new areas of study in science. All of this comes at a fraction of the cost and size of alternative x-ray sources such as synchrotrons and free electron lasers. In this talk, I will discuss how we produce and optimise our x-ray beam, present some of our results and discuss our plans for future experiments.
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| New Eyes on the Universe: astronomical instrumentation in the 21st century |
| Prof Ray Sharples |
University of Durham |
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14:30, Friday 8 February 2008 | | Physics Seminar Room (Building 46/5081) |
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Progress in astronomy is closely coupled to developments in astronomical technology and instrumentation. This talk will review the recent advances which have been made in developing instruments for the current generation of large 8-10m diameter ground-based telescopes, and the challenges posed by future extremely large (20-40m diameter) telescopes. Specific technical advances will be illustrated via new instruments being developed at the Centre for Advanced Instrumentation in Durham.
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| Velocity-Map Imaging of Chemical Events |
| Dr Claire Vallance |
University of Oxford |
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14:30, Friday 1 February 2008 | | Physics Seminar Room (Building 46/5081) |
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Work in the field of chemical reaction dynamics is aimed at understanding the detailed physics underlying chemical reactivity. In recent years, the field has been revolutionised by the introduction of velocity-map imaging, a technique which provides a direct snapshot of the reaction product scattering distribution with single particle resolution. This talk will outline the history and capabilities of the velocity-map imaging technique, with examples taken from research carried out within our group, and will also preview some future developments.
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| Sculpting Behaviour by Evolution |
| Dr Mario de Bono |
University of Cambridge |
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14:30, Friday 25 January 2008 | | Physics Seminar Room (Building 46/5081) |
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Out in the wild the nematode Caenorhabditis elegans lives by eating bacteria in rotting vegetation. Over the past 40 years this worm has been domesticated in the lab and is now probably the best understood multicellular organism. We are studying how its network of precisely 302 neurons allows it to forage for food, and how, at the level of molecules and neural circutis, foraging behaviour evolves across wild populations. I will focus in particular on responses to food and ambient oxygen.
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| Super Supercritical Fluids |
| Dr David Smith |
University of Southampton |
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14:30, Friday 18 January 2008 | | Physics Seminar Room (Building 46/5081) |
(Sadly, David has forgotten to let me have an abstract for his talk, but I think I can remember the gist...)
Supercritical fluids are the moaning Minnies of the fluid world, worked up into such a heated, high pressure lather that they can no longer distinguish substance from hot air. Their cutting criticism penetrates deeply into nanoscale structures, transporting bile and venom to hitherto inaccessible recesses. Shunning superficial attractions, supercritical fluids may know the cost of everything and the value of nothing, but they are about to revolutionize the deposition of functional nanostructured films, facilitate a new class of hitherto diffusion-limited chemical reactions, and single-handedly save the world from global warming.
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| Rough Guide to The Moon and Mars |
| Prof Mike Lockwood |
University of Southampton |
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14:30, Friday 11 January 2008 | | Physics Seminar Room (Building 46/5081) |
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This talk will provide a survival guide for those of you thinking of venturing into inter-planetary space, and an exploration of the many and diverse hazards that the intrepid space traveller must risk or endure.
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| Optical Sculpting and Optical Binding |
| Prof Colin Bain |
University of Durham |
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14:30, Friday 14 December 2007 | | Physics Seminar Room (Building 46/5081) |
This talk will describe two areas of current research in which we use optical forces to control the organisation and shape of objects on micron and sub-micron length-scales.
The surface tension of oil droplets is normally many orders of magnitude larger than the force constant of optical tweezers, with the result that small emulsion droplets are not measurably deformed by focussed light beams. Close to microemulsion phase boundaries, the interfacial tension of oil-in-water emulsions drops to ultralow values. Optical tweezers can then be used to deform micron-sized oil droplets into predetermined shapes. When a single oil drop is divided into two with a pair of optical tweezers, the daughter drop remains connected to the parent drop by an invisible thread of oil of nanometric diameter. Optical pressure can be used to drive flow between droplets connected by such a nanothread. Strategies can be developed for creating 3-way junctions between nanothreads and for making closed loops of droplets connected by threads.
The technique of optical trapping, in which scattering of light by single particle leads to a force on that particle, is well-known. Multiple scattering of laser light can also give rise to a force between particles, a phenomenon known as optical binding. Optical binding can result in spontaneous creation of ordered particle arrays, known as ‘optical matter'. Interesting dynamical effects, with analogies to atomic crystals, are observed.
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| Global Remote Sensing of the Atmospheric Electromagnetic Environment |
| Dr Martin Füllekrug |
University of Bath |
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14:30, Friday 7 December 2007 | | Physics Seminar Room (Building 46/5081) |
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The atmospheric electromagnetic environment of the Earth is explored with low frequency electromagnetic waves. The locations of lightning discharges around the globe are determined with a global magnetometer network to monitor the temporal and spatial evolution of particularly intense thunderstorms. Above these thunderstorms, an exotic type of lightning occurs, denoted sprites. Sprites are associated with electrical breakdown in the mesosphere and electrically couple the troposphere with the ionosphere. Sprites are a new element in the global atmospheric electric circuit which may play a critical role in fair weather cloud formation.
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| Harnessing Light with Plasmons |
| Prof Bill Barnes |
University of Exeter |
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14:30, Friday 30 November 2007 | | Physics Seminar Room (Building 46/5081) |
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In this colloquium we will look at the physics underlying plasmonics - and at some of the features that make it an attractive and exciting topic of current research.
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| Testing Time-Reversal Symmetry |
| Dr Ben Sauer |
Imperial College, London |
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14:30, Friday 23 November 2007 | | Physics Seminar Room (Building 46/5081) |
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Many extensions to the Standard Model violate time reversal symmetry. In particular, Supersymmetry predicts rather large time reversal violating electric dipole moments of fundamental particles. I will describe our experiment to search for T violation using YbF molecules, a particularly sensitive system. I will describe our new molecular beam techniques for sensitive measurements of E and B fields, as well as discussing the current status of the T violation experiment.
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| A Fat-Free Three-Step Guide to Surface Plasmon Polaritons |
| Dr Dominic Zerulla |
University College, Dublin |
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14:30, Friday 16 November 2007 | | Physics Seminar Room (Building 46/5081) |
Surface Plasmons (SPs), widely recognized in the field of surface science following the pioneering work by Ritchie, are electromagnetic surface waves propagating along the interface of two materials with dielectric functions of opposite sign. They are essentially light waves that are trapped on the surface as a result of interactions between the illuminating wave and the free electrons of the conductor, and are called Surface Plasmon Polaritons (SPPs) to reflect this hybrid nature. Recent advances in fabrication technologies have created new opportunities to control SPP properties to reveal new aspects of their underlying science, and to tailor them for specific applications.
After a short introduction into SPP excitation, this talk will focus on SPP propagation on nanostructured surfaces, tuneability of SPPs arising from metamaterials and focusing aspects of SPPs.
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| VECSELS: Colourful Solid-State Lasers |
| Dr Jennifer Hastie |
University of Strathclyde |
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14:30, Friday 2 November 2007 | | Physics Seminar Room (Building 46/5081) |
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Vertical external cavity surface emitting lasers (VECSELs) are optically-pumped solid-state lasers with the advantage of a semiconductor gain region. High brightness combined with the wavelength flexibility available through semiconductor bandgap engineering leads to a versatile laser source that may be tailored to a particular application, from the ultraviolet to the mid-infrared. An overview of these lasers will be given with attention to thermal management and spectral coverage, focussing on the red and ultraviolet.
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| Engineering in Yacht Design for the 2007 America's Cup |
| Mr Ian Campbell |
University of Southampton |
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14:30, Friday 26 October 2007 | | Physics Seminar Room (Building 46/5081) |
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The University of Southampton has had a long association with the America's Cup through the work of the Wolfson Unit. For the 2007 Cup Ian Campbell, a Wolfson Unit research engineer, became part of the Luna Rossa challenge design team, with particular responsibilities for their experimental research programmes. Here, he will give an overview of the engineering development work involved in designing the yachts, which is aimed at improving their performance.
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| Why Aren't There Any... Magnetic Liquids? |
| Prof Kevin O'Grady |
University of York |
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14:30, Friday 19 October 2007 | | Physics Seminar Room (Building 46/5081) |
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Ferrofluids - paramagnetic suspensions of magnetic nanoparticles - exploit a bizarre range of physical phenomena, forming spontaneous corrugations in the presence of an external field, showing thermal convection when heated above the Curie temperature, and adhering to magnetized moving parts. As a result, they also find an extremely diverse variety of scientific and industrial applications, from coolants and lubricants to adaptive shock absorbers and actuators. With the aid of a number of practical demonstrations, Prof O'Grady will discuss the many fascinating aspects of these remarkable fluids.
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| Seismology of Solar Activity |
| Prof Mike Thompson |
University of Sheffield |
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14:30, Friday 12 October 2007 | | Physics Seminar Room (Building 46/5081) |
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Helioseismology provides a unique probe of the solar interior. In this talk, Prof Thompson will discuss recent results from helioseismology in particular relating to temporal variations of the interior dynamics and the emergence of magnetic flux.
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| A Chip-Scale Differential Atomic Magnetometer |
| Dr Eleanor Hodby |
NIST, Boulder |
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14:30, Friday 5 October 2007 | | Physics Seminar Room (Building 46/5081) |
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This talk will give a brief overview of the chip-scale atomic devices work at NIST, Colorado, which began with the development of an atomic clock no larger than a grain of rice. Dr Hodby will discuss the principles of atomic magnetometry before describing the design and operation of the new chip-scale differential magnetometer in detail.
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| Quantum Optics with Macromolecules: balls, string and little elephants |
| Prof Markus Arndt |
University of Vienna |
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14:30, Friday 15 June 2007 | | Physics Seminar Room (Building 46/5081) |
Research on matter waves is currently a thriving field of quantum physics, and coherence experiments with complex objects are of particular interest for exploring the quantum-to-classical transition, for precisely measuring molecular properties, and for testing new models of space-time.
Prof Arndt's group has performed the first experimental realization of a new interferometer type which is particularly well suited for demonstrating the wave-particle duality of "large things". Here, Prof Arndt will report experiments using the new device with molecular balls, pancakes and strings, and discuss the conditions needed to see even the interference of a small 'molecular elephant' in the near future. Various applications will be considered, regarding both the foundations of physics and measurements in physical chemistry.
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| Atoms Stripped (Almost) Bare: the physics of highly charged ions |
| Dr David Crosby |
University of Oxford |
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14:30, Friday 8 June 2007 | | Physics Seminar Room (Building 46/5081) |
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Highly charged ions are atoms that have been stripped of most of their electrons. The comparatively high ionization energies required in order to produce such systems mean that highly charged ions occur in association with many hot and violent phenomena such as active galactic nuclei and magnetically confined fusion plasmas. Highly charged ions also represent an extreme of atomic physics where relativistic and quantum electrodynamic effects lead to changes of the usual rules and expectations. In this talk, Dr Crosby will provide an overview of the physics of highly charged ions and some of their applications. He will also describe a particular device used for the study of highly charged ions, the electron beam ion trap (EBIT), and discuss experiments that seek to test aspects of fundamental atomic physics using highly charged ions.
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| The Enigma Machine and the Bombe |
| Mr Frank Carter |
Bletchley Park Trust |
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14:30, Friday 1 June 2007 | | Physics Seminar Room (Building 46/5081) |
Just outside what is now Milton Keynes, and perhaps strategically mid-way between Oxford and Cambridge, Bletchley Park was the centre of one of the most remarkable achievements of the Second World War: the repeated breaking of the German military signals codes. These heroic efforts, by a disparate band of academics, emigres, and servicemen and women, represented a colossal activity that Churchill considered to have changed the direction of the war; yet, despite the involvement of many thousands of people, the entire operation remained an untold secret until the 1970s. The incredible story is also that of the invention of the computer, which developed from the machines developed at Bletchley as crucial parts of the code-breaking processes.
Mr Carter will focus on one major aspect of Bletchley's extensive wartime history: the breaking of the Enigma ciphers and the development of the machines to do this. He will begin with a brief account of the history of the Enigma machine and how it was used operationally by the German Armed Forces during WWII. He will then explain the design of, and rationale behind, the remarkable 'Bombe' that was developed to break the Enigma ciphers by Alan Turing and Gordon Welchman, from an original pre-war machine invented by Polish mathematicians. The operation of the Bombe will be illustrated with the aid of a small electrical model.
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| From HEP to HEP: high energy physics to highly entangled proteins |
| Prof Dick Blankenbecler |
Stanford University |
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14:30, Friday 18 May 2007 | | Physics Seminar Room (Building 46/5081) |
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Prof Blankenbecler - emeritus professor at the Stanford Linear Accelerator (SLAC) - will discuss his remarkable scientific voyage from high energy particle scattering via photonic display elements to biophysics, including recent work to deduce the 3D structure of proteins from x-ray diffraction patterns, enabling the study of their functional and ancestry relationships, and current projects to reduce the discomfort associated with cancer treatment.
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| Going Round the Bend with Bose-Einstein Condensates |
| Dr Aidan Arnold |
University of Strathclyde |
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14:30, Friday 11 May 2007 | | Physics Seminar Room (Building 46/5081) |
The concept of atoms as particles is familiar to many, however at the microscopic level classical physics breaks down, and we enter the wave-like realm of quantum mechanics. If vapours of bosons are cold and dense enough a phase transition occurs in which all of the atoms coalesce into the same (lowest energy) quantum state – a Bose-Einstein condensate (BEC), in which all of the atomic wave-functions are coherent. These "atom lasers" are extremely cold (~50nK) and allow textbook quantum mechanics to be played out on a simple CCD camera.
Dr Arnold will give an overview of the processes required to obtain BEC, briefly sidetracking into atomic lenses, before discussing the construction of the Strathclyde 10cm diameter storage ring for cold atoms and BECs. He will then present recent experimental BEC/storage ring results from his group, including a gravitational beamsplitter for BECs. The Strathclyde system will be ideal for studying condensate collisions and for precise Sagnac interferometry.
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| Maximizing Entropy for Fun and Profit |
| Dr Geoff Daniell |
University of Southampton |
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14:30, Friday 4 May 2007 | | Physics Seminar Room (Building 46/5081) |
Geoff's talk will describe the background justification to the Maximum Entropy method of assigning values to probabilities. He will then give very rapid and superficial accounts of three applications: Statistical Mechanics, The National Lottery and Data Processing.
No previous knowledge will be assumed and the talk should be understandable and of interest to all physicists including undergraduates (in fact some of the material is taken from Geoff's lectures on thermal physics).
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| Novel Tools for Ocean Science |
| Prof Gwyn Griffiths |
University of Southampton |
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14:30, Friday 20 April 2007 | | Physics Seminar Room (Building 46/5081) |
Progress in ocean science is often dependent on our capacity to make observations. The Underwater Systems Laboratory develops new platforms, such as autonomous underwater vehicles, that are capable of carrying sensors to otherwise inaccessible parts of the ocean, for example beneath sea ice and floating ice sheets. Remotely operated vehicles provide an intervention capability for observation and sample collection in the deep ocean, while underwater gliders enable unattended long endurance measurements at low cost.
However, for many parameters no suitable in situ sensor yet exists. USL works closely with several academic schools to devise new sensors, often through cosupervised students. Recent examples include measuring methane using a Surface Plasmon Resonance device and characterising phytoplankton species using automated cytometry and electrical impedance spectroscopy using microchips designed and constructed at the University.
The talk will cover the science drivers, examples of advances in ocean science from the developments at USL, elements of the technologies employed and some of the gaps in capability and will conclude with an outline of our core programme for the next 5 years.
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| Optical Tweezers: microbubbles and nanotubes |
| Dr Phil Jones |
University College, London |
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14:30, Friday 16 March 2007 | | Physics Seminar Room (Building 46/5081) |
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Optical tweezers - that is a single beam optical dipole trap for microscopic objects - have many applications across the physical, chemical and life sciences. In this talk I will review how optical tweezers work before discussing, and presenting results from, our recent experiments with two technologically interesting optically trappable objects: microscopic coated gas bubbles and carbon nanotubes.
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| The Diamond Synchrotron Light Source |
| Dr Sarnjeet Dhesi |
Rutherford-Appleton Laboratory |
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14:30, Friday 2 March 2007 | | Physics Seminar Room (Building 46/5081) |
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The Diamond 3GeV synchrotron, which opened to its first scientific users last month, is the largest and most expensive UK science facility of recent decades. The third-generation light source uses arrays of magnets to generate extremely intense, narrow beams of radiation at energies from meV IR through to >40keV x-rays, 10,000 times brighter than Daresbury, for research applications across the physical, life, earth and environmental sciences.
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| Quantum State Engineering with Single Atoms, Photons and Electrons |
| Dr Matt Jones |
University of Durham |
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14:30, Friday 16 February 2007 | | Physics Seminar Room (Building 46/5081) |
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How big can a quantum state be? Answering this question has turned into an exciting area of research spanning quantum optics, atomic physics and condensed matter. One approach is to try to build up many-body quantum states from individual quantum systems. Dr Jones will present recent experimental results on controlling the quantum state of single rubidium atoms trapped in an optical tweezer, and will describe how we can couple these atoms to another quantum system - single photons - in a controlled way. A second "top-down" approach is to try to access and control the state of individual particles in a larger, interacting many-body system. How this might be done using electron transport in ultra-cold strontium atoms will be outlined.
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| Weighing the Antiproton: precision laser spectroscopy of antiprotonic helium atoms |
| Prof Ryugo Hayano |
CERN & University of Tokyo |
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14:30, Friday 9 February 2007 | | Physics Seminar Room (Building 46/5081) |
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Antiprotonic helium is a metastable three-body neutral atom consisting of an antiproton, a helium nucleus and an electron. The antiproton, which normally annihilates within a few picoseconds when injected into matter, can be "stored" in the antiprotonic helium atom for up to several microseconds, and laser spectroscopy is possible within this time window. From the laser transition frequency, the antiproton-to-electron mass ratio can be deduced, and in our recent measurement, we determined the antiproton-to-electron mass ratio to be 1836.152674(5). In the seminar, I will discuss how we discovered this exotic system, how we observe the laser resonance, and implications of our recent results on the CODATA fundamental constant adjustments as well as on the matter-antimatter symmetry tests.
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| Colour Centres in Diamond as Practical Singel-Photon Sources |
| Dr Francois Treussart |
Ecole Normale Superieur de Cachan |
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14:30, Friday 2 February 2007 | | Physics Seminar Room (Building 46/5081) |
Nitrogen-Vacancy (N-V) colour centres in diamond show stable room temperature photoluminescence of unsurpassed efficiency and, optically excited in a pulsed fashion, offer clock-triggered single-photon pulses. Efficient extraction of the emitted photons is however thwarted by the high diamond refractive index, for refraction at the sample interface leads to a small collection solid angle due to total internal reflection, and strong optical aberrations. An efficient solution uses sub-wavelength diamond nanocrystals, rendering refraction irrelevant and allowing the colour centres to radiate essentially as if they were point sources in air.
This talk will describe a "turn-key" single-photon source based on (N-V) colour centre photoluminescence inside dispersed diamond nanocrystals. Following J. A. Wheeler's seminal ideas, we have used the emitted single photons to realize a wave-particle delayed-choice experiment based on a Mach-Zehnder interferometer. The measurement at the output of the interferometer is randomly switched between either the registration of the "which-path" information for the photon or the observation of the interference fringes. As predicted by quantum mechanics, we observe no difference between a so-called "normal-choice" and a "delayed-choice" experiment where the switching process takes place only after the photon passes the first beamsplitter of the interferometer.
We have also investigated the application of our single-photon sources to open-air quantum key distribution (QKD). Broad-band colour centre emission in the (N-V) system precludes day-light QKD operation, but other colour centres in diamond, related to nickel impurities, show striking new features, with narrow band emission around 800 nm that is almost entirely concentrated in the zero phonon line even at room temperature. With a short photon emission lifetime around 2 ns, these sources pave the way to efficient open-air single-photon QKD in day-light operating conditions.
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| Blue Sky Research: the polarization of daylight |
| Dr Mark Dennis |
University of Southampton |
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14:30, Friday 19 January 2007 | | Physics Seminar Room (Building 46/5081) |
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A little-known fact is that the polarization of the natural blue sky of daylight contains polarization singularities (polarization vortices), where the degree of polarization vanishes. They were discovered by observation in the 1800s, explained approximately by Rayleigh scattering, and their detailed prediction was one of the successes of Chandrasekhar's radiative transfer theory in the 1950s. Here, Dr Dennis will discuss their topological properties: as simple examples of polarization singularities, they organize the pattern of polarization in skylight. A simple mathematical ansatz is consistent both with observations and Chandrasekhar's theory. Dr Dennis will also discuss connections between this work and polarization singularities in the electromagnetism of dielectrics, and in spatially-varying random polarization patterns.
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| How Can We Solve the Maths Problem? |
| Dr David Acheson |
University of Oxford |
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14:30, Friday 12 January 2007 | | Physics Seminar Room (Building 46/5081) |
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Why are so many people scared stiff of mathematics? All too often, the real truth is that they have never been allowed anywhere near it. In this lecture, Dr Acheson will suggest how anyone can appreciate something of mathematics at its best, including elegant lines of reasoning, surprising results and remarkable applications, ranging from the dynamics of the electric guitar to whether mathematics can explain the legendary Indian Rope Trick.
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| From Einstein's Intuition to Quantum Bits: a new quantum age? |
| Prof Alain Aspect |
Institut d'Optique, Université de Paris-Sud |
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14:30, Friday 8 December 2006 | | Physics Seminar Room (Building 46/5081) |
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According to quantum mechanics, the Einstein-Podolsky-Rosen paradox predicts that two particles may be connected by a 'ghostly action at a distance', whereby a measurement on one particle instantly determines the state of the other, even before light could have travelled between the two. This scenario drives right to the heart of quantum mechanics, suggesting that there might be pre-determined 'hidden variables' that the quantum measurement process simply reveals. John Bell's analysis of this interpretation indicated that the existence or otherwise of hidden variables could be determined experimentally ("Bell's inequalities"). The experiment was then performed in an exceptionally clear and elegant fashion by Aspect, Dalibard and Roger in 1982. "The results," read the abstract, "are in good agreement with quantum mechanical predictions but violate Bell's inequalities by 5 standard deviations." The experiment is one of the very few from the last 50 years to enter our standard textbooks, and paved the way for the remarkable new technique of quantum cryptography.
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| Self-Organized Nanoparticle Assemblies: a panoply of patterns |
| Prof Philip Moriarty |
University of Nottingham |
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14:30, Friday 1 December 2006 | | Physics Seminar Room (Building 46/5081) |
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Nanoparticle-solvent films deposited on solid substrates are associated with a rich dynamic behaviour which gives rise to a wide variety of striking self-organised patterns. Although close-to-equilibrium self-assembly of nanoparticle arrays has been studied in some depth, there has been rather less work on solvent-nanoparticle systems driven far from equilibrium (via, for example, spin coating). In the far-from-equilibrium regime, a remarkably broad array of intricate, spatially correlated patterns form including "foam-like" cellular networks, labyrinthine structures similar to those formed in spinodal decomposition of binary fluids, and well-defined fractal morphologies. I shall focus on our recent results in two areas: (i) "coerced coaresening" of nanoparticle arrays where the system is mechanically driven towards equilibrium, and (ii) the use of scanning probe-defined silicon oxide patterns to direct solvent dewetting and thus form colloidal nanoparticle corrals.
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| Cold Antihydrogen |
| Prof Jochen Walz |
Johannes-Gutenberg Universität Mainz |
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14:30, Friday 24 November 2006 | | Physics Seminar Room (Building 46/5081) |
Cold antihydrogen atoms have been produced at CERN's Antiproton Decelerator (AD) by mixing trapped antiprotons and positrons. The internal structure of antihydrogen atoms has been probed and their velocity has been measured. This talk will discuss experiments of the ATRAP collaboration.
Future high-resolution laser-spectroscopy of antihydrogen in a magnetic trap can provide extremely precise tests of the fundamental symmetry between matter and antimatter (CPT symmetry). Yet another exciting long-term perspective is that ultra-cold antihydrogen atoms might enable the first measurement of the gravitational acceleration of antimatter. For both types of experiment cooling of antihydrogen atoms is essential. This talk will discuss conventional and novel cooling methods.
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| Cold Molecules and Ultracold Chemistry |
| Prof Tim Softley |
University of Oxford |
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14:30, Friday 17 November 2006 | | Physics Seminar Room (Building 46/5081) |
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A range of methods being developed in our laboratory for the production of cold and ultracold molecules in the gas phase (T< 1K), including ions, neutrals and Rydberg molecules, will be discussed, and I will report on progress towards collisional studies with these translationally cold species.
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| The Dark Side of the Universe |
| Prof Joe Silk |
University of Oxford |
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14:30, Friday 10 November 2006 | | Physics Seminar Room (Building 46/5081) |
One of the greatest mysteries in the cosmos is that it is mostly dark. That is, not only is the observed night-sky dark, but also most of the matter in the universe - whose existence is clearly inferred from the observations - is dark. For every atom visible in planets, stars and galaxies today there exists at least five or six times as much "Dark Matter" in the universe. Astronomers today are seeking to unravel the nature of this mysterious, but pervasive dark matter, and determine whether it can ever be detected.
I will review the current status of these searches.
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| Slow Light in Photonic Crystal Waveguides |
| Prof Thomas Krauss |
University of St Andrews |
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14:30, Friday 3 November 2006 | | Physics Seminar Room (Building 46/5081) |
In an age where faster is better, the proposition to improve photonic devices by slowing light down seems an odd idea. Nevertheless, slow light offers many opportunities, based on the fact that it yields stronger light-matter interactions. Increased linear and nonlinear effects for switches and modulators, as well as the prospect of photonic memory are motivating much research in this area.
Slow light can be created in dielectric materials via resonances in cavities or in photonic crystals. In the case of dielectric structures, the refractive index contrast is the key parameter determining the performance of the system, so high refractive index structures such as photonic crystals appear particularly promising. While slow light in photonic crystals has been observed by a variety of authors, the operating point is typically near the edge of the Brillouin zone, which is naturally dispersive. Slow light in photonic crystals therefore tends to coincide with high dispersion, which removes most of the advantages and severely limits the bandwidth that can be utilised. In fact, dispersive broadening has been observed to outweigh the pulse compression one would otherwise expect.
Luckily, the large parameter-space available in photonic crystal waveguides allows the design of waveguides with controlled dispersion. We also found a slow light regime in a W2 waveguide away from the band-edge that exhibits slow light over a considerable bandwidth and that has allowed us to demonstrate pulse compression, commensurate with the reduction in group velocity, by a factor of 25.
Another aspect of slow light in photonic crystals is that of propagation loss. Since loss scales with the square of disorder, it is essential to refine the technology to its absolute limit. We have achieved propagation losses in W1-type waveguides of below 5 dB/cm. Furthermore, we observe losses to scale linearly with slowdown factor, which is encouraging given that several authors have previously claimed an S2 dependence. This indicates that devices exploiting slow light phenomena are indeed realistic.
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| A Quantum Approach to Friction |
| Prof Steve Barnett FRS |
University of Strathclyde |
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14:30, Friday 27 October 2006 | | Physics Seminar Room (Building 46/5081) |
As students we learn how to introduce frictional losses into mechanics as a slowing force proportional to a particle's velocity. This leads, of course, to a steady state for unforced systems in which the particle is stationary. At a more microscopic level, however, thermal effects on the motion cannot be ignored and we enter a regime in which Brownian motion dominates. We can describe this in a simple way by adding a fluctuating random force, the effect of which is to ensure a never ending thermal agitation. The description of this phenomenon in terms of molecular motion was, of course, one Einstein's great contributions in 1905.
At the level of quantum dynamics, the description of friction is anything but straightforward. At the simplest level we run into difficulties with commutation relations. Analyses based on model environments inevitably seem to lead either to memory effects or to unphysical heating or thermal runaway, neither of which is present in classical dynamics. I shall describe a simple approach to modeling quantum friction based on the physics of collisions as measurements. The resulting dynamics has many of the appealing features of the classical Brownian motion but with some inevitable quantum subtleties.
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| The Dazzler: a programmable acousto-optic dispersive filter |
| MM. Pierre Tournois & Daniel Kaplan |
Fastlite, Paris |
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14:30, Friday 20 October 2006 | | Physics Seminar Room (Building 46/5081) |
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The talk will describe how, with only a simple acousto-optic crystal in line in the laser beam, one can program a precisely known spectral phase into a broadband femtosecond pulse. Various applications of this device will be discussed. We shall emphasize its recent use to quantitative phase measurements, allowing to switch between methods such as autocorrelation, SPIDER, FROG, etc., without changing the optical set-up.
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| Ancient Astronomy: the Egyptian View of the Sky |
| Dr Sarah Symons |
University of Leicester |
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14:30, Friday 13 October 2006 | | Physics Seminar Room (Building 46/5081) |
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Astronomical activity in ancient Egypt is frequently linked with religious ritual, but several forms of astronomical information (such as astronomical diagrams and star clocks) contain evidence of long-term observational practices. We will look at textual sources, astronomical instruments, and graphical representations of the sky, and discuss the extent and applications of astronomical knowledge in ancient Egypt.
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| John Herschel - astronomer, artist, and much more |
| Prof Brian Warner |
University of Cape Town |
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14:30, Friday 28 July 2006 | | Physics Seminar Room (Building 46/5081) |
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Son of the more famous William Herschel, John Herschel was one of the most extraordinary polymaths in the 9th centure. The lexture will describe and illustrate his life as an astronomer, mathematician, physicist, artist, inventor and generally all-round good chap.
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| Timing Is Everything: femtosecond pulse control on a multi-beam light source |
| Dr Graeme Hirst |
Rutherford Appleton Laboratory |
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14:30, Friday 16 June 2006 | | Physics Seminar Room (Building 46/5081) |
The next generation of accelerator-based light sources will deliver broadly tunable radiation pulses in the femtosecond regime. These will be used to extend existing laser techniques and to develop new science in previously inaccessible parts of the spectrum.
However this will only be possible if the timing of the pulses can be managed at the femtosecond level across installations which will be hundreds or thousands of metres in size. This talk will outline the substantial challenges arising from this requirement and will describe some of the creative solutions, based largely on modern laser and fibre-optic technology, which are being developed to meet it.
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| Beta-Sheet Fibrils: money for old rope? |
| Dr Cait MacPhee |
University of Edinburgh |
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14:30, Friday 2 June 2006 | | Physics Seminar Room (Building 46/5081) |
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Beta-sheet protein fibrils are linear and unusually stable aggregates most commonly associated with a number of degenerative diseases, including Alzheimer's, Parkinson's and type-II diabetes. In disease states their formation is typically a result of the impairment of metabolic pathways or cellular function. In contrast to this villainous activity, recent evidence suggests that they may also have beneficial roles in nature including controlling osmotic flow, mediating surface adhesion, and moderating surface tension. These physico-mechanical properties suggest their utility in a wide range of surface applications and their self-assembly ability suggests their use as scaffolds in the development of novel materials. This talk will describe recent advances in protein nanotechnology, and explore the properties of natural and artificial fibrillar protein scaffolds that may make them useful as self-assembling nanoscale materials.
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| The Path to Fusion Power |
| Prof Sir Chris Llewellyn-Smith FRS |
UKAEA Culham |
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14:30, Friday 26 May 2006 | | Physics Seminar Room (Building 46/5081) |
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Fusion, which powers the sun and stars, is potentially an environmentally responsible and intrinsically safe source of essentially limitless energy. The Joint European Torus (JET) has produced 16 MW of fusion power, and construction of a power station sized device called ITER (International Tokamak Experimental Reactor), which should produce at least 500 MW, is about to begin. An International Fusion Materials Irradiation Facility (IFMIF) is also needed to test materials that will have to stand up to years of intense neutron bombardment in a fusion power station. Given its potential attarcations (which include essentially limitless fuel, and the absence of green-house gas, or other emissions, and of long-lived radio-active by-products), and that the economics of fusion power look acceptable, the time has come to develop fusion as rapidly as reasonably possible. The status and potential advantages of fusion will be described, together with the outstanding challenges, remaining steps and timetable for developing fusion power.
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| Optical Micromanipulation Takes Hold |
| Prof Kishan Dholakia |
University of St Andrews |
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14:30, Friday 12 May 2006 | | Physics Seminar Room (Building 46/5081) |
Optical tweezing is a powerful non-contact technique where micrometre sized particles can be grabbed, moved and generally manipulated solely with light. Optical tweezers have forged an important bridge between physics, chemistry and biology. In recent years there has been a proliferation of activity in this area, fuelled, in part, by the recognition that we need to advance the "optical toolkit" particularly for microfluidic environments.
In this talk, Prof Dholakia will give an overview of this technique and discuss a variety of current important themes in this field including creation of large scale optical landscapes, trapping and organisation on a surface including the use of surface plasmons and cavity enhanced fields. Particle-particle interactions may lead to "optical binding" which may lead to self -assembly. Finally (and time permitting), biophysics applications will be described including optical sorting and photoporation of cells.
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| Molecular Diodes and Single Molecule Electronics |
| Mr Geoff Ashwell |
Cranfield University |
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14:30, Friday 5 May 2006 | | Physics Seminar Room (Building 46/5081) |
To mimic the functions of silicon-based devices it is necessary to make electrical contact to molecules that self-organise, the shortest active sequence being metal|donor-acceptor|metal. It is described as a molecular diode when the organic moieties are linked via an electron bridge and as a rectifying junction when they are simply in physical contact. There are few examples and the published rectification ratios are too small to have any real significance, the values being typically 2-30 at ±1 V for Langmuir-Blodgett and self-assembled monolayers contacted by non-oxidisable electrodes. However, new methods of self-organisation have provided greatly improved behaviour with rectification ratios in excess of 3000 at ±1 V for Au|Au-S-C10H20-A+-π-D|D-|Au devices where a cationic acceptor-(π-bridge)-donor molecule is ionically coupled with an anionic donor. Rectification ratios from these ultra-thin structures are on a par with electrical asymmetries reported for metal-insulator-metal devices where oxide-induced Schottky barriers dominate the behaviour.
The properties of novel rectifying molecules will be presented together with recent data from studies on prefabricated nanoscale structures for single molecule electronics.
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| Nanoplasmonics: generation and control of nanoscale optical fields |
| Prof Mark Stockman |
Georgia State University |
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14:30, Friday 24 March 2006 | | Physics Seminar Room (Building 46/5081) |
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Nanoplasmonic phenomena are based on the resonant excitation of surface plasmons, causing highly enhanced and localized optical fields on the nano-scale. These fields induce a multitude of enhanced optical effects, in particular, surface enhanced Raman scattering (SERS) including single-molecule SERS, enhanced second- and third-harmonic generation, and enhanced two-photon electron emission from nanostructured surfaces, with many existing and prospective applications in nanoprobing, ultrasensitive detection and biomedical monitoring. This talk will include a broad introduction to the topic and also certain forefront, focus areas based partially on original contributions, including ultrafast, coherent, nonlinear, and stimulated phenomena.
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| Planar Nano-Structured Meta-Materials |
| Prof Nikolay Zheludev |
University of Southampton |
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14:30, Friday 17 March 2006 | | Physics Seminar Room (Building 46/5081) |
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In nanophotonic applications, planar meta-materials can deliver most of functionalities normally expected from bulk optical devices, from spectral selectivity to lensing, and from polarization sensitivity to non-reciprocity.
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| Hot Air Balloons: special shapes and record breakers |
| Mr David Boxall |
Flying Pictures Space Ltd |
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14:30, Friday 10 March 2006 | | Physics Seminar Room (Building 46/5081) |
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The beguiling beauty of hot air balloons belies a wealth of fascinating physical principles that account for their flight, shape and behaviour, and which may be exploited to produce the most spectacular special shapes - from flying cows to dinosaurs, pagodas and motorbikes. In the realm of record-breaking flights, these characteristics and limitations come to the fore. David Boxall will describe and illustrate the many delightful and fascinating aspects of balloon design behind the glamorous and entrancing advertising balloons of the 1990s, and the latest stratospheric record breakers - including the Breitling III round-the-world balloon, the QinetiQ-1 edge-of-space attempt, and last year's world altitude record.
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| Dielectric Cavity QED at the Cutting Edge |
| Prof Mohamed Babiker |
University of York |
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14:30, Friday 3 March 2006 | | Physics Seminar Room (Building 46/5081) |
Prof Babiker will review some early experiments on field confinement from which cavity QED emerged as an inter-disciplinary field, and describe the current status of cavity QED at the micro- and nano-scales. This scenario is currently regarded as promising for the realisation of scalable solid state quantum information processing. Current and recently published work on microstructures characterised by sharp edges, involving dielectric and metallic films, will then be described. Emitters, such as quantum dots and F-centres embedded near the sharp edges can experience huge modifications of their radiative characteristics. Concepts such as self entanglement arise in such contexts, allowing the control of the transfer of excitation between emitters, including those separated by metallic screens. He will also describe proof-of-principle experiments, being carried out at York. Recent advances in precision implantation and the ability to create structures of any desired composition, shape and size, mean that experimental work in the optical region will be successfully undertaken in the near future.
The talk will have very few mathematical formulae displayed.
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| Cavity QED with Trapped Ions |
| Dr Eoin Phillips |
University of Innsbruck |
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14:30, Friday 17 February 2006 | | Physics Seminar Room (Building 46/5081) |
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Atoms trapped and well-localized in an optical cavity allow for the investigation of cavity QED effects. We have built a system for such experiments and plan to demonstrate single-ion lasing and a deterministic single-photon source. The set-up may also allow for atom-atom entanglement via the cavity mode and deterministic atom-photon entanglement in the future.
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| Nonlinear optical microscopy |
| Prof Allister Ferguson |
University of Strathclyde |
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14:30, Friday 10 February 2006 | | Physics Seminar Room (Building 46/5081) |
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The field of optical microscopy has been transformed by the introduction of two-photon fluorescence. The progress that has taken place in nonlinear microscopy over the past decade will be reviewed, concentrating on the developments in novel light sources for microscopy and advanced multiphoton microscopy techniques. Progress will be illustrated using examples from the life sciences.
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| Keeping bright light behind bars |
| Prof Philip Russell |
University of Erlangen |
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14:30, Friday 27 January 2006 | | Physics Seminar Room (Building 46/5081) |
Photonic crystal fibres (PCFs) have attracted increasing scientific and technological interest since the first example was reported in 1996.
Although superficially similar to a conventional hair-thin glass optical fibre, PCF has a unique microstructure, with an array of microscopic hollow channels running along its entire length. These channels act as optical barriers or scatterers and, suitably arranged, can "corral" light within a central core (either hollow or made of solid glass). PCF can trap light in two ways: by a modified form of total internal reflection, when the core has a higher average refractive index than the photonic crystal cladding; and by a two-dimensional photonic bandgap, for which the core can instead be hollow.
Light can be controlled and transformed in these fibres with unprecedented freedom, allowing the precision guidance of light in a narrow hollow core, highly nonlinear PCFs with accurately controlled dispersion, fibres that guide only one mode at all wavelengths, and stimulated Raman scattering at threshold powers six orders of magnitude lower than usual. These are just a few examples of how the PCF concept has ushered in a new and more versatile era of fibre optics, with a multitude of applications spanning many areas of science.
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| Polarized neutron scattering - techniques and applications |
| Dr Ross Stewart |
ILL Grenoble |
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14:30, Friday 20 January 2006 | | Physics Seminar Room (Building 46/5081) |
Neutron polarization analysis studies of materials (magnetic materials, polymers, biological systems...) can give unambiguous information on both structural and dynamical properties.
However, the polarization and analysis of the neutron beam has a high cost in counting rate, making measurements long and prone to systematic errors. New developments such as 3He neutron spin-filters and large supermirror arrays are making polarized neutron techniques more attractive - allowing polarization analysis to be performed using large detector arrays, resulting in a major increase in counting rate.
An overview of the current state-of-the-art in polarized neutron scattering will be presented.
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| Dispersive Properties of Coherently Prepared Media |
| Dr Ifan Hughes |
Durham University |
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14:30, Friday 16 December 2005 | | Physics Seminar Room (Building 46/5081) |
Doppler-free spectroscopy of atomic media has become a standard technique in many important research areas such as laser cooling and metrology. However, whereas measurements of Doppler-free absorption are commonplace, measurements of the concomitant dispersion spectra are relatively rare.
Direct measurement of optical dispersion is both of fundamental interest, for example relating to the phenomena of "slow" and "trapped" light in media exhibiting Electomagnetically Induced Absorption (EIA), and in applications providing a reference for active stabilisation of a laser frequency.
Recent results using a Sagnac interferometer to measure the dispersion of a thermal rubidium vapour in a non-linear pump-probe experiment exhibiting a sub-natural linewidth will be presented.
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| Is It Entirely Superstition? |
| Prof Emeritus Heinz Wolff |
Institute for Bioengineering, Brunel University |
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14:30, Friday 9 December 2005 | | Physics Seminar Room (Building 46/5081) |
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Prof. Heinz Wolff, old enough to indulge himself in some disreputable science, will investigate whether there could conceivably be any "scientific" rationale behind long standing "superstitions" in matters such as water divining and Astrology. This will be a light-hearted event, spiced with an attempt at public experimentation. An open mind is welcomed. Coloured slides will be shown!
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| Frustration and Spin Fluctuations |
| Prof Brian Rainford |
University of Southampton |
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14:30, Friday 2 December 2005 | | Physics Seminar Room (Building 46/5081) |
The topology of crystals can have profound effects on their magnetic properties. A trivial example is that no long range magnetic order can exist in one dimension. In two and three dimensions we can find "frustrated" systems, which have highly degenerate ground states and hence no long range order.
Examples are the hexagonal net (Kagome) lattice (2d) or the 3d pyrochlore lattice with antiferromagnetic interactions. These have spin liquid ground states. We have been working on frustrated itinerant magnets. in this case the frustration not only inhibits long range order, but also the formation of the local moment. Neutron scattering allows us to measure the spectra of spin fluctuations in the nearly-formed magnetic moments. I will give some examples of our recent work on beta-Mn and some pseudo one-dimensional magnetic metals.
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| Adaptive Optics in Astronomy and Vision Science |
| Prof Chris Dainty |
NUI Galway |
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14:30, Friday 25 November 2005 | | Physics Seminar Room (Building 46/5081) |
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Adaptive optics uses the active correction of wavefront distortions to achieve the best resolution or acuity from optical systems that range from massive telescopes to the human eye. It allows the correction of a variety of imperfections, from natural aberrations to atmospheric distortions, and can even be applied to allow imaging within human tissue and the study of how birds see. Prof Dainty will discuss the application of adaptive optics to a range of topics in astronomy and vision science currently being studied by his group in Galway.
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| Solar Variability and Climate Change |
| Prof Joanna Haigh |
Space and Atmospheric Physics, Imperial College London |
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14:30, Friday 11 November 2005 | | Physics Seminar Room (Building 46/5081) |
Since ancient times, and the observation of variations in sunspot numbers, it has been speculated that changes in solar activity may influence the climate on Earth. The scientific literature provides a large number of examples of studies claiming correlations between different solar and meteorological parameters, although many of these do not stand rigorous statistical analysis and, until recently, the whole subject area was viewed with mistrust, if not derision, by the meteorological establishment.
Since the availability of solar irradiance measurements from earth-orbiting satellites, however, it has been established that the solar "constant" is not. Furthermore, advances in computer power have enabled the development of sophisticated climate models that can incorporate many of the relevant processes.
This talk will outline the chequered history of solar-climate studies, review the evidence for an influence of the Sun on the lower atmosphere and discuss recent work using numerical circulation models that are helping to unravel some of the physical mechanisms involved.
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| Spin Manipulation in III-V Semiconductors |
| Prof Richard Harley |
University of Southampton |
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14:30, Friday 4 November 2005 | | Physics Seminar Room (Building 46/5081) |
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Spins in semiconductors can form a basis for new spintronic and quantum data processing devices in which quantum wells and two-dimensional electron gases play a central role. Richard will discuss the optical control and measurement of electron and nuclear spins and their dynamics, leading to the design of new spintronic devices.
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| High Intensity Laser Pulses - a new frontier in laser science |
| Prof Jon Marangos |
Imperial College, London |
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14:30, Friday 21 October 2005 | | Physics Seminar Room (Building 46/5081) |
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| The Physics of Foams |
| Prof Denis Weaire |
Trinity College, Dublin |
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14:30, Friday 14 October 2005 | | Physics Seminar Room (Building 46/5081) |
Liquid foams present a variety of interesting physical properties, often reflected in everyday life and sometimes of great importance to industry. They behave as solids when gently squeezed, and as liquids when subjected to large forces. Such behaviour earns them the name 'soft matter'. Examples include emulsions, such as non-drop paint, and liquid crystals.
This talk will be a broad survey of recent developments and historical background with a few surprises, such as foam in the Beijing Olympics.
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| Plasmon Waveguides and Resonators |
| Dr Stefan Maier |
California Institute of Technology |
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14:30, Friday 24 June 2005 | | Physics Seminar Room (Building 46/5081) |
Research into electromagnetic surface modes or surface plasmon polarities confined to interfaces between a metal and a dielectric has a rich history dating back to the mid-20th century. More recently, the emergence of sophisticated nanofabrication techniques has allowed fabrication of nanoscale metal patterning and led to intense research efforts due to potential applications in novel metal-based wavelength and subwavelength-scale photonics devices.
One basic building block of such devices is the plasmon waveguide that guides electromagnetic energy in the visible and near-infrared regime of the electromagnetic spectrum. Energy transport at telecommunication wavelengths using micron-size metal slabs has been demonstrated, and the guiding at near-infrared and visible frequencies using nanowires and arrays of closely spaced metal nanoparticles is a step toward the ultimate goal of building highly integrated photonics circuits with spatial dimensions below the diffraction limit. These guiding structures may also find other practical applications, such as delivering energy to "hot-spots" for biological sensing.
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| The Galaxy Redshift Survey: baryon oscillations and cosmological constraints |
| Dr Shaun Cole |
Durham University |
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14:30, Friday 17 June 2005 | | Physics Seminar Room (Building 46/5081) |
Giant maps of the Universe reveal that galaxies are clustered on large scales into vast filaments and sheets, separated by huge voids. The exact nature of these distributions reflects in a particularly sensitive fashion the composition of the Universe - the relative proportions of dark energy, dark matter and baryons.
The Two Degree Field (2dF) Galaxy Redshift Survey used the unique capabilities of the Anglo-Australian Observatory to examine 221,414 galaxies covering 3% of the sky. The detailed data obtained allow the matter content of the Universe to be inferred, showing evidence of 'baryon oscillations' and constraining the dark matter energy density. The data are consistent with other results from the Sloan Digital Sky Survey and the COBE and WMap space telescopes.
By extrapolating the present mass distribution backwards through time, the early evolution of the Universe can be determined. The galaxies we see today prove to result from tiny irregularities, due to quantum or subatomic processes, which were present at the birth of the Universe, and which have been amplified by gravity ever since.
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| Ultrafast Spectroscopy and Force Imaging: photo-dynamics and imaging onthe life science interface |
| Prof Mike Towrie |
Rutherford Appleton Laboratory |
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14:30, Friday 10 June 2005 | | Physics Seminar Room (Building 46/5081) |
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The present capabilities and future developments of picosecond Raman, Mid-Infrared, near-IR and visible spectroscopy and novel single molecular force probe will be described. Experimental measurements exploiting the time resolved infrared and Raman capability will be presented. For example recent observations of the excited state and energy relaxations pathways of nucleotides and nucleotide polystrands will be presented. These measurements provide insight into the mechanisms that DNA has evolved to protect against radiation damage.
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| Negative Index Materials for Optical Frequencies: applications to sub-wavelength imaging and lithography |
| Prof Gennady Shvets |
University of Texas and Austin |
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14:30, Wednesday 8 June 2005 | | Physics Seminar Room (Building 46/5081) |
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Electromagnetic properties of periodic plasmonic nanostructures can be engineered using the concept of electrostatic resonances. Remarkably, nanostructures consisting of non-magnetic parts (such as metallic nanorods) can be configured in such a way that they exhibit magnetic properties in the optical frequency range. Such negative permittivity/negative permeability waves can be used for constructing an optical super-lens capable of sub-wavelength resolution. I will also present simulation results demonstrating that more complicated shapes of nanoparticles can be used to make a low-loss negative index material in the near-infrared. Experimental results demonstrating super-lensing in mid-infrared spectral range using ultrathin films of silicon carbide will also be presented.
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| Amateur Rocketry |
| Mr Rick Newlands |
UK Rocketry Association; AspireSpace |
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14:30, Friday 3 June 2005 | | Physics Seminar Room (Building 46/5081) |
Building and launching your own rocket must be every schoolboy's dream - and that too of every engineering student! From first experiments in a shared house in Burgess Road, Rich Newlands has been involved in amateur rocketry from his days as a Southampton undergraduate, continuing the proud tradition of learning by experience that dates back to the Paisley pioneers of the 1950s. In this talk, he will tell the tale of how the first haphazard devices have evolved into well-understood, advanced rockets capable of carrying telemetry to astonishing altitudes.
From early experiments of dubious reliability and legality, UK amateur rocketry has developed into an impressively capable and professional community, which regularly launches home-made rockets to altitude in excess of 30,000 feet - with the full knowledge and cooperation of aviation and police authorities. Through AspireSpace, Rick and his colleagues have been developing new, powerful but simple rocket motors, closely related to those chosen by Burt Rutan to power SpaceShipOne for the first private space flights last year.
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| Spin Injection and Control in Semiconductors |
| Dr Yuzo Ohno |
Tohoku University |
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14:30, Friday 20 May 2005 | | Physics Seminar Room (Building 46/5081) |
Semiconductor spin-electronics (spintronics), where both charge and spin degrees of freedom are utilized, is currently of great interest. This is because it is expected to enable integration of magnetic functionalities and semiconductor circuitry as well as quantum information technology based on coherent nature of spins in semiconductors. For developing practical semiconductor "spintronics" devices, injection of spin-polarized electrical current into non-magnetic semiconductors is one of key elements. For a number of spin-based device schemes, electrical spin injection through high quality semiconductor heterojunctions in the absence of magnetic field is preferable.
We have investigated and demonstrated the electrical spin injection and local control of electron and nuclear spins in semiconductor quantum wells. Further developments in fabrication of magnetic/non-magnetic semiconductor nanostructures and manipulation of electron and nuclear spins will pave the way to future spintronics devices.
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| Probing Electronic Structure with Positrons |
| Dr Stephen Dugdale |
University of Bristol |
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14:30, Friday 13 May 2005 | | Physics Seminar Room (Building 46/5081) |
The Fermi surface is of tremendous importance in solid-state physics. Besides characterising the ground state of a metallic system, and determining its transport and magnetic properties, it is thought to be behind many other important phenomena. The reason is that only those electrons near the Fermi surface can repined to external fields by incremental absorption of energy, for electrons which are deeper in the 'Fermi sea' have no unoccupied states into which to move.
Fermi surfaces are not, in general, simple spheres, and the determination of their often complicated topologies remains an important challenge for solid-state physicists. Significant information can be derived from measurements of the gamma-photons emanating from electron-positron annihilation when the sample is irradiated with positrons. Relying only on the conservation laws of energy and momentum, the positron technique is not restricted to low temperature and ordered phases, and provides an invaluable window on the electronic structure of room temperature and disordered alloys.
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| The Optics of Butterfly Wings |
| Prof Roy Sambles FRS |
University of Exeter |
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14:30, Friday 6 May 2005 | | Physics Seminar Room (Building 46/5081) |
The wings of butterflies and moths are adorned with a wealth of pattern and colour unrivalled in the living world. Iridescent colours can be among the purest and most brilliant, unmatched in depth and intensity by even the brightest pigments. The glittering change of hue that accompanies any change of angle lends these colours a remarkable magic and beauty.
The origins of iridescent colours have been long discussed. Newton, in Opticks (1704), proposed a reason for the iridescent colour of peacock feathers, but the true credit for their explanation goes to his contemporary Robert Boyle. More than a hundred years later, interference was explained in detail by the English physicist Thomas Young.
The surface of the wings of these insects is composed of thousands of very small scales and it is from these that the wing colours and patterns originate. These scales show spectacular multilayer structures, whose diversity and complexity place Lepidopteran scales among the most complicated extra-cellular structures that are manufactured by a single cell. In some cases, tiny fern-like structures form miniature multilayer films that support the interference from multiple reflectors within them.
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| Optical Beams with Interesting Beam Cross-Sections |
| Dr Ole Steuernagel |
University of Hertfordshire |
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14:30, Friday 29 April 2005 | | Physics Seminar Room (Building 46/5081) |
A simple explanation of the features of focussed optical beams with interesting profiles is given, using the fact that they are equivalent to quantum harmonic oscillators. The resulting understanding of the properties of focussed beams is then put to use.
Tailored time-dependent variations of teh transverse profile together with longitudinal phase shifts of laser beams are studied. And it is shown that a standing wave set-up and real-time beam forming techniques (e.g. by computer-addressed holograms) can make it possible to implement smooth transport across and along the beams employed in optical trapping schemes. Novel modes for the efficient collectin, transport, and concentration of trapped particles should thus become realizable in optical trapping set-ups, specifically for tiny particles such as cold atoms.
Although this is mostly a theory talk, some experimental results will be shown.
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| Silly Ideas |
| Dr David Jones (Daedalus) |
University of Newcastle |
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14:30, Friday 22 April 2005 | | Physics Seminar Room (Building 46/5081) |
Weekly, from 1964 until 2003, the delightfully plausible but improbable inventions of Daedalus and his activities for DREADCO entertained and inspired the readers of firstly New Scientist and subsequently Nature and the Guardian. Aimed at "a region of scientific humour whose appeal lay in its closeness to reality", these ideas were intended purely to entertain; yet, with the passage of time, what initially appeared virtually impossible often became reality. From the production of prototype structures by uv actuation of photopolymer (proposed in 1982; reality by 1988) to the invention of Buckminsterfullerene (Daedalus 19661; Kroto et al., 19852), some 17% of Daedalus's inventions have so far come true - and the fraction is still rising! Silly ideas, Dr Jones enthusiastically insists, are worth taking seriously!
In addition to his world-renowned exploits as Daedalus, David Jones is perhaps best known for the modern theory of bicycle stability3, his determination of arsenic in Napoleon's wallpaper4 and his series of perpetual-motion machines - the latest of which is in the Technisches Museum, Vienna.
1 New Sci. 32, 245 1966
2 Nature 318, 162 1985
3 Physics Today, 34 April 1970
4 Nature 299, 626 1982
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| Quantum Information Science with Trapped Yb+ Ions |
| Prof Christof Wunderlich |
NUI Maynooth and University of Siegen |
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14:30, Friday 18 March 2005 | | Physics Seminar Room (Building 46/5081) |
Electrodynamically trapped 171Yb+ ions are well suited to serve as qubits in investigations related to quantum information processing (QIP). It is shown, for example, that the production of 171Yb+ ions by photoionisation of Yb is simple, isotope selective, highly efficient and allows for nearly deterministic loading of ion traps.
Recent work employing 171Yb+ for QIP includes the nearly optimal estimation of an unknown quantum state using a self-learning algorithm. The estimation of an unknown quantum process is at the centre of further experiments where different quantum channels are experimentally realised and reconstructed from experimental data.
In future experiments, ion molecules will be realised that exhibit long-range pairwise spin-spin coupling and are suitable, for instance, for experimental investigations at the border of quantum information science and condensed matter physics.
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| Navigation for the D-Day Landings |
| Mr Walter Blanchard G3JKV |
Royal Institute of Navigation |
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14:30, Friday 11 March 2005 | | Physics Seminar Room (Building 46/5081) |
While the invention of radar just before the Second World War, by Robert Watson-Watt and his team from the National Physical Laboratory, was crucial to the Battle of Britain and the defence against enemy bombers, the direction of British aircraft to targets over the Channel came to rely upon another application of radio to navigation, conceived in 1937 by R. J. Dippy - another of Watson-Watt's Bawdsey Manor group. GEE worked by measuring the delay in reception between pulses transmitted simultaneously from different ground stations and, together with Alex Reeves; OBOE, began a series of developments in hyperbolic radio navigation which subsequently led to the Decca, LORAN and ultimately GPS systems in use today.
Walter Blanchard, an ex-RAF navigator, expert in radio navigation and recent President of the Royal Institute of Navigation, will discuss the history of radio navigation and its particular role on D-Day when, among other achievements, Oboe precision bombing allowed the destruction of nine of the ten heavy guns that threatened the Allied landings.
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| Physics from Colloids - Einstein's legacy in contemporary condensed matter physics |
| Prof Wilson Poon |
University of Edinburgh |
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14:30, Friday 4 March 2005 | | Physics Seminar Room (Building 46/5081) |
2005 is the centenary of Einstein's annus mirabilis, during which he invented the light quantum, formulated special relativity, and explained Brownian motion. The latter achievement is perhaps the greatest, since it directly led to the wide-spread acceptance of the reality of atoms. As part of his theory of Brownian motion, Einstein deduced the so-called barometric distribution of a suspension of particles in a gravitational field. He showed that under some circumstances, colloids behaved as 'big atoms'. Einstein's theoretical formulation was verified by Perrin's experiments (for which the latter received the Nobel Prize).
The paradigm of 'colloids as big atoms' has undergone something of a renaissance in the last two decades. Soft condensed matter physicists experiment with well-characterised colloids to gain insights into a variety of fundamental questions in condensed matter and statistical physics. In this talk, I will give two examples: how the studies of colloids has given new insights into the existence of liquids, and the nature of glassy states.
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| Antihydrogen |
| Prof Mike Charlton |
University of Wales, Swansea |
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14:30, Friday 25 February 2005 | | Physics Seminar Room (Building 46/5081) |
Antimatter has fascinated scientists, and captured the public's imagination, ever since its existence was predicted by Paul Dirac in 1931. How fitting then that in 2002, the year we celebrated the centenary of Dirac's birth, antihydrogen - the bound state of an antielectron (positron) and an antiproton - was created under controlled conditions for the first time.
The antimatter landmark was achieved by the ATHENA antihydrogen collaboration working at CERN's Antiproton Decelerator facility. Opened only 4 years ago, this allows physicists to study antiprotons at very low energies, and the production of antihydrogen has been a key aim. Short bursts of antiprotons are collected and confined in an electromagnetic Penning trap, where a sample of around 10,000 is cooled to around 15 degrees above absolute zero. The confining potential is then gently lowered and the antiprotons are allowed to mix with positrons stored in a positron accumulator and, in a complex dynamic process, many antihydrogen atoms are formed.
With data from more than 50,000 antihydrogen events already amassed, we can now look forward to a variety of physics studies on antihydrogen - in particular precise comparisons of its spectrum with that of ordinary hydrogen, that will provide stringent tests of the so-called CPT theorem, which predicts subtle differences between the behaviour of matter and antimatter.
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| Towards Quantum Information Processing using Self-Assembled Quantum Dots |
| Dr Mark Fox |
University of Sheffield |
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14:30, Friday 18 February 2005 | | Physics Seminar Room (Building 46/5081) |
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Quantum information processing has three main branches: quantum cryptography, quantum computing, and quantum teleportation. In this colloquium I will explain how self-assembled quantum dots might be used in all three branches of the subject, and will give a brief overview of the present state of the art in the experimental implementations. I will then review the relevant work that is underway in Sheffield, with particular focus on single and entangled photon sources, and spin dynamics. The progress is very encouraging, but there are still many difficulties to be overcome.
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| Patterns in the Sand |
| Prof Tom Mullin |
University of Manchester |
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14:30, Friday 11 February 2005 | | Physics Seminar Room (Building 46/5081) |
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Why does sand dry around your feet when you walk along a wet beach? This and other fundamental physics questions will be discussed when Prof Mullin describes his research into the flow of complex materials, and how modern mathematical ideas can be applied to laboratory and numerical experiments. At the Manchester Centre for Nonlinear Dynamics, Prof Mullin has developed a 17-metre long pipe system - the world's biggest computer-controlled syringe - which allows the experimental demonstration of spectacular effects in granular flows. Such research gives a completely new way of trying to solve the greatest problem in classical physics - why liquid flowing through a pipe becomes turbulent. If we can solve that, we can control it and bring order to chaos.
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| Cold Molecules, Time-Reversal Symmetry and Physics Beyond the Standard Model |
| Dr Mike Tarbutt |
Imperial College, London |
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14:30, Friday 17 December 2004 | | Physics Seminar Room (Building 46/5081) |
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The measured value of the electron's electric dipole moment (edm) is, at the present level of experimental uncertainty, consistent with zero. Most extensions to the standard model predict a value that is non-zero and within reach of the most sensitive experiments. A non-zero value violates both parity and time-reversal symmetries. Certain highly polarizable molecules allow for an exceptionally sensitive measurement of the electron edm. At Imperial College, Mike et al are using ytterbium fluoride molecules to perform such a measurement. In order to maximize the sensitivity of their experiment, the group forms cold molecules and is developing methods to decelerate these molecules to rest and trap them. The talk will outline the principle and current status of these experiments.
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| Optical Angular Momentum |
| Prof Steve Barnett FRS |
University of Strathclyde |
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14:30, Friday 10 December 2004 | | Physics Seminar Room (Building 46/5081) |
We are used to the idea that light carries energy and linear momentum. Hardly less familiar is the idea of an angular momentum associated with the degree of circular polarisation. It is only within the last dozen years, however, that the orbital angular momentum of light has become a topic of serious study. In this lecture, I will describe the nature and origin of both optical spin and orbital angular momentum and illustrate the differences with some experimental results.
In the quantum regime, orbital angular momentum is well-defined and has been measured at the single photon level. It is also possible to change the angular momentum of light in nonlinear optical processes and to create photons entangled in orbital angular momentum. Angular momentum is conjugate to angular position, in analogy with the corresponding linear quantities. The periodicity in angular position leads to significant differences to the linear case, however, and to a different uncertainty relation. I will describe these unfamiliar features and present our experimental confirmation of this uncertainty bound.
Finally, physicists have debated for a century the correct form of the momentum of light inside a dielectric medium. I will describe two extreme views, ascribed to Abraham and Minkowski, and a simple analysis of our planned experiment aimed at distinguishing between them.
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| Nanoscale Magnetic Imaging |
| Dr Simon Bending |
University of Bath |
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14:30, Friday 3 December 2004 | | Physics Seminar Room (Building 46/5081) |
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| The Discovery and Physics of the Double Pulsar System |
| Prof Andrew Lyne FRS |
Jodrell Bank Observatory, University of Manchester |
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14:30, Friday 26 November 2004 | | Physics Seminar Room (Building 46/5081) |
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Prof Lyne - director of the Jodrell Bank observatory - will discuss the discovery last year of the first known double pulsar: a 22-millisecond pulsar in a nearby 2.4-hour eccentric binary system with a companion which is a 2.7-second radio pulsar. The presence of the second detectable pulsar promises to make this an important test-bed for new rigorous tests of strong-field gravity and general relativity and for probing the magnetospheres of radio pulsars.
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| Ultrafast Coherent Spectroscopy |
| Dr Wolfgang Langbein |
University of Cardiff |
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14:30, Friday 19 November 2004 | | Physics Seminar Room (Building 46/5081) |
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The optical characteristics of microscopic 'quantum dot' structures prove to be quite unlike most of the more macroscopic optical resonators to which we are accustomed. For technological applications, they offer lasers with lower thresholds and higher gain and tunability than conventional devices, but their characterization requires higher spatial and temporal resolution. Ultrafast coherent spectroscopy allows the determination of many of the optical properties and gain dynamics in these fascinating mesoscopic structures, whose coherent quantum mechanical evolution truly merits the description of 'artificial atoms'.
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| The Sonar of Dolphins |
| Dr Peter Dobbins |
University of Bath |
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14:30, Friday 12 November 2004 | | Physics Seminar Room (Building 46/5081) |
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Finding the next meal in the dark is a problem dolphins and many other creatures have solved using sound. By combining models of radar and sonar with our knowledge of bioacoustics we can explore how these animals' accomplishments exceed the capabilities of man-made systems. This talk will concentrate on how the dolphin's 'hardware' is ideal for spatially localising a target.
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| Adaptive Eyecare: optical innovation for the third world |
| Prof Josh Silver |
University of Oxford and Adaptive Eyecare Ltd |
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14:30, Friday 29 October 2004 | | Physics Seminar Room (Building 46/5081) |
Josh began work on his invention nearly 20 years ago, modernising and developing an idea that dates back to the 18th century. Initially, it was simply to see if they could be made but, realizing that he could build something with the potential to help millions of people, he decided that he "ought to just go out and give it a go." Two decades later, the adaptive spectacles look like ordinary ones except for knobs each side of the frame that adjust the curvature of the lens: wearers adjust each lens to their own requirements, and can alter the focus if their eyesight deteriorates over time.
With just 50 opticians for a population of almost 20 million, it would take on average about 200 years to be seen by an optometrist in Ghana - but adaptive glasses obviate the need for a trip at all. Trials in the country since 1996 proved instantly successful:"There was one girl who didn't know trees have leaves," said Ghanaian eye surgeoun Dr Kweku Ghartey, "You should have seen the smile on her face when she understood that the leaves she found on the ground came from the trees." Through a deal with the WHO and the World Bank, Prof Silver plans to sell up to 400,000 adaptive glasses in Ghana, with another 9.3 million pairs in South Africa in the pipeline.
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| Slowing and Focussing Molecules with Pulsed Optical Fields |
| Dr Peter Barker |
Heriot-Watt University |
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14:30, Friday 22 October 2004 | | Physics Seminar Room (Building 46/5081) |
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The optical dipole force may be used for the manipulation and transport of ensembles of atoms and molecules. In particular, we are studying the transport induced within periodic potentials formed by travelling optical lattices, in both hollow optical fibres and in free space. Lattices moving with a constant velocity form a light force pump, which can both transfer and separate the transported species. Accelerating lattices, produced from frequency chirped, high intensity lasers, allow the acceleration of molecular beams to high energies or, alternatively, their slowing to low temperatures. The periodic modulation in density of gases and plasmas within an optical lattice also offers a new form of temperature probe.
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| From Prescriptive Programming of Solid-State Devices to Orchestrated Self-Organization of Informed Matter |
| Dr Klaus-Peter Zauner |
University of Southampton |
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14:30, Friday 15 October 2004 | | Physics Seminar Room (Building 46/5081) |
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Achieving real-time response to complex, ambiguous, high-bandwidth data is impractical with conventional programming. Only the narrow class of compressible input-output maps can be specified with feasibly sized programs. Efficient physical realizations are embarrassed by the need to implement the rigidly specified instructions requisite for programmable systems. The conventional paradigm of erecting stern constraints and potential barriers that narrowly prescribe structure and precisely control system state needs to be complemented with a new approach that relinquishes detailed control and reckons with autonomous building blocks. Brittle prescriptive control will need to be replaced with resilient self-organization to approach the robustness and efficiency afforded by natural systems.
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| Quantum Cryptography and Single Photon Devices |
| Dr Andrew Shields |
Toshiba Research Europe Ltd |
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14:30, Friday 25 June 2004 | | Physics Seminar Room (Building 46/5081) |
Quantum cryptography is the first true application of quantum mechanics at the single quantum level. Based upon the ‘ghostly action at a distance' of entangled-state measurement - addressed by Einstein, Podolsky and Rosen in 1935 – it offers absolute security of communication, whereas conventional encryption systems rely upon the complexity of the eavesdropper's task.
Quantum cryptography presents new challenges in the need for entangled photon sources and single photon detectors. Developments in these crucial technologies have allowed quantum communication to be demonstrated through distances of over 100km.
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| Single-Electron Dynamics in Semiconductor Quantum Dots |
| Dr Toshimasa Fujisawa |
NTT Basic Research Labs |
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14:30, Friday 18 June 2004 | | Physics Seminar Room (Building 46/5081) |
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| Quantum Manipulation of Single Atomic Ions |
| Dr Danny Segal |
Imperial College, London |
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14:30, Friday 4 June 2004 | | Physics Seminar Room (Building 46/5081) |
That information processing has anything to do with physics may come as a surprise. The very concept of information is, however, inextricably linked to those of energy and entropy. The action of 'Maxwell's demon', for example, is essentially an exercise in gaining information about the positions and momenta of the particles in the system: it is this insight which put to rest the 'paradox' that had exercised physicists for generations.
Quantum information processing begins with quantum cryptography, where the nature of quantum measurement is exploited to encode, send and decode information in a way that can be proved to be secure – not because of the complexity of the eavesdropper's task, but thanks to the laws of physics. Quantum cryptography depends on the quantum descripiton of light and the manipulation of photons, and its hardware comprises novel light sources, optical fibres and interferometers.
While photons can be used for information transfer, storage implies rather longer timescales and requires the use of individual atoms, ions, Josephson junctions or quantum dots – which are also governed by quantum mechanics. Information processing exploits the creation of superposition states of a single quantum system and entangled states of more than one quantum system – fundamentally non-classical operations which will ultimately allow quantum algorithms to perform tasks which, on acceptable timescales, classical computers will find impossible.
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| Voltage-Tunable Optics of a Quantum Dot |
| Dr Richard Warburton |
Heriot-Watt University |
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14:30, Friday 28 May 2004 | | Physics Seminar Room (Building 46/5081) |
Quantum dots are nanometre-scale clusters that confine electrons in all three directions, and can be made using standard growth techniques as islands of low band-gap semiconductor in a higher band-gap sea. These ‘artificial atoms' have a valence band which contributes strong optical transitions that are the basis for laser action, optical storage and fluorescence. Just as with atoms, the emission energy changes abruptly whenever an electron is added, with a pattern analogous to Hund's rules in atomic physics.
In practice, the dots which are grown vary in size, shape and composition, and these fluctuations affect any form of spectroscopy you care to measure. Such broadening is eliminated by studying single quantum dots, with the necessary resolution afforded by a cryogenic confocal microscope, further enhanced by using nanometre-sized holes in a metal mask. We are also working on the design of nano-cavities for the application of quantum dots in laser structures.
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| Light's Angular Momentum: it's all torque |
| Prof Miles Padgett |
University of Glasgow |
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14:30, Friday 21 May 2004 | | Physics Seminar Room (Building 46/5081) |
That light beams carry both linear momentum and spin is of course no surprise. That they also carry an orbital angular momentum has only been a subject of study in the last decade.
This orbital angular momentum can be transferred to matter (an optical spanner) and when such beams are rotated results in a measurable frequency shift. Similarly to the spin component, the orbital angular momentum is both a classical and a quantum observable. Most recently, we have observed an angular manifestation of Heisenberg's Uncertainty principle where the observed spread in angular momentum is set by the angular restriction within the light beam. This last effect gives a new approach to secure communication.
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| Novel Surface-Emitting Photonic Devices based upon III-V Semiconductors |
| Dr Martin Dawson |
University of Strathclyde |
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14:30, Friday 14 May 2004 | | Physics Seminar Room (Building 46/5081) |
Group III-V compound semiconductors form the basis of modern optoelectronics technology, enabling semiconductor lasers, light-emitting diodes, photodetectors and other specialised devices for applications in areas as diverse as optical data storage, telecommunications, and displays. So ubiquitous is this technology that the current worldwide market for compound semiconductors is currently $10 billion per annum, and showing double-digit per annum growth.
VECSELs are an exciting new category of semiconductor laser, analogous to diode-pumped doped-insulator crystal lasers but where the gain element is a VECSL-like semiconductor structure. These lasers offer wavelength flexibility from uv to near infra-red, Watt-level output in high-quality beams and external cavity operation suitable for single-frequency operation or mode-locking.
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| Gravitational Wave Detection - Opening a New Window on the Universe |
| Prof Ken Strain |
University of Glasgow |
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14:30, Friday 7 May 2004 | | Physics Seminar Room (Building 46/5081) |
Gravitational waves are ripples in space-time, predicted by Einstein in his General Theory of Relativity and produced by the acceleration of distant masses. The extreme weakness of the gravitational interaction means that even the most violent astrophysical events barely produce effects at the limits of detectability, and massive laser interferometric detectors must operate close to their fundamental quantum limits if any but the rarest events are to be observed.
This new window on the universe promises unique information about a variety of astrophysical systems - supernova explosions, pulsars and coalescing compact binary systems - in much the same way that radio and x-ray telescopes have revolutionized observational astronomy. Ken's talk will cover the GEO 600 prototype detector in Hanover, LIGO in the USA, and the projected space-borne gravitational wave experiment LISA.
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| The Micromaser: a proving ground for quantum physics |
| Dr Ben Varcoe |
University of Sussex |
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14:30, Friday 30 April 2004 | | Physics Seminar Room (Building 46/5081) |
Ben's research concerns the fundamental mechanism at the heart of the laser: how a single optical mode interacts with a lone two-level atom - the most basic system possible in quantum mechanics. The simplicity of this system has made it the most commonly studied theoretically, while experimental work in the guise of the Micromaser has allowed a series of remarkably elegant practical demonstrations of the beauty and mystery of quantum mechanics.
The Micromaser is based around highly reflecting microwave cavities which, by repeated reflection, can store light for up to a third of a second. The phenomena observed, which are purely quantum in origin, thus occur on macroscopic timescales, in which the dynamics can be observed in great detail.
Current research on the Micromaser is investigating methods of controllably "entangling" atoms to create a useable quantum resource, with potential applications from fundamental tests of quantum mechanics to quantum computing and quantum information. Future miniaturization will allow such technology to be incorporated in single atom chip devices.
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| Trapped Ion Optical Frequency Standards and Metrology |
| Dr Helen Margolis |
National Physical Laboratory |
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14:30, Friday 23 April 2004 | | Physics Seminar Room (Building 46/5081) |
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Helen's research concerns new and improved ways of measuring time. These are based upon frequency standards, derived from optical transitions in single atomic ions which, for the most precise measurements, must be isolated, trapped and cooled to within a fraction of a degree of absolute zero. A gloriously elegant device called a frequency comb (based around holey optical fibres) is then used to measure the optical frequency, or to provide the "clockwork" needed to turn the frequency standard into a truly optical clock. The remarkable precision achievable allows the most precise measurements of a range of fundamental constants, and even offers an investigation of their potential variation as the universe ages.
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