Welcome 
 Research 
     dipole forces 
     stim. scattering 
     coherent control 
 Literature 
 People 
 Join us! 
 Contacts 
 Teaching 
 Useful links 

Quantum Control - undergraduate dissertations

THE STATE OF QUANTUM MECHANICS AT CHRISTMAS 1926

Dr Tim Freegarde   email: tim.freegarde@soton.ac.uk   Room: 5071
The theory of quantum mechanics developed at an astonishing rate in the 1920's, as recorded in a torrent of papers from some of the most famous names in physics. Some papers were truly seminal and took the subject forwards in a single bound, yet all were also based upon an already established body of physics and mathematics.
By 1926, many of the key elements of modern quantum mechanics had been established. Heisenberg had already introduced his matrix representation, and Schrödinger was about to present the wave equation that now bears his name; yet key elements, including the uncertainty principle, remained to follow. Understanding and resolving quantum mechanics was the most important challenge of the time, and the Solvay conference the following year attracted an astonishing attendance: Planck, Einstein, Dirac, de Broglie, Born, Bohr, Ehrenfest, Schrödinger, Pauli and Heisenberg were all present.
This dissertation will seek to establish the state of quantum mechanics at the end of 1926, including its experimental and mathematical origins and the specific developments achieved in that year itself.

THE MOMENTUM OF LIGHT IN MEDIA: THE ABRAHAM-MINKOWSKI CONTROVERSY

Dr Tim Freegarde   email: tim.freegarde@soton.ac.uk   Room: 5071
Two classic calculations of the momentum carried by an electromagnetic field disagree as to whether the momentum is increased or decreased by the presence of a refractive medium. This dissertation will explore the various interpretations and attempts to rationalize the two approaches, as well as recent suggestions that subtle consequences of the two theories might be experimentally observable. The project will touch upon the orbital angular momentum of light, and further manifestations of wave-particle duality.

CAVITY-MEDIATED OPTICAL COOLING AND TRAPPING OF ATOMS AND MOLECULES

Dr Tim Freegarde   email: tim.freegarde@soton.ac.uk   Room: 5071
Optical cooling and trapping techniques which exploit the force of laser light can cool atoms to within a nanoKelvin of absolute zero. These techniques, and the remarkable quantum phenomena which govern such cold systems, won the Nobel prizes in 1997 and 2001. Similar mechanisms can be used to trap and manipulate macroscopic particles, such as biological cells, using 'optical tweezers', while on a still larger scale, optical forces are responsible for the dust tails of comets and, if an impending space mission proves successful, they may soon be used to propel spacecraft using 'solar sails'.
Although molecules have so far eluded the techniques of laser cooling, several potential mechanisms have been proposed. Amongst the more promising is the use of resonant optical cavities to provide both field enhancement and the crucial dissipative mechanism that is fundamental to the cooling process. A review of the various cavity-mediated cooling and trapping schemes to have been proposed and, occasionally, investigated will make a fascinating and topical dissertation.

THEORY AND APPLICATIONS OF ACOUSTIC LEVITATION FORCES

Dr Tim Freegarde   email: tim.freegarde@soton.ac.uk   Room: 5071
The optical dipole force - the mechanism behind 'optical tweezers' - may be regarded as deriving from the recoil imparted when the photons of a beam of light are deflected by optical refraction. A similar force accompanies the refraction of any other momentum-carrying wave, and sound waves in air have been shown capable of levitating tungsten ball bearings. This dissertation will explore the principles underlying the acoustic levitation force, and possible applications of tailored acoustic fields from remote assembly to particle sorting.