Coherent control

Optical mechanisms can be destroyed by non-radiative processes such as vibrational redistribution, which lead to decoherence and rapid population loss. Recent studies have shown that such effects can be reduced by coherent control, in which quantum interference between multiple excitation pathways is used to cancel coupling to the unwanted, non-radiative channels. To achieve this, the chirps used for stimulated scattering must be replaced by more generally tailored fields derived, for example, by adaptive spectral filtering of femtosecond laser emission. Current examples of coherent control range from electromagnetically-induced transparency and VSCPT (velocity-selective coherent population trapping) to the selection of product channels in chemical reactions.