"Light at bicycle speed…and slower yet !"
Light pulses have been slowed in a Bose-Einstein condensate to only 17 m/s, more than seven orders of magnitude lower than the light speed in vacuum. Associated with the dramatic reduction factor for the light speed is a spatial compression of the pulses by the same large factor. A light pulse, which is 1-2 miles long in vacuum, is compressed to a size of ~50 µm, and at that point it is completely contained within the atom cloud. This further allows the light pulse to be completely stopped and stored in the atomic medium for up to several milliseconds, and subsequently regenerated with no loss.
With the most recent extension of the method, the light
roadblock, light pulses have been compressed from 2 miles to only 1-2 µm.
This system has been used to generate the superfluid analogue of shock
waves, Quantum Shock Waves, in Bose-Einstein condensates. These dramatic
excitations result in the formation of solitons that in turn decay into
quantized vortices - created far out of equilibrium, in pairs of opposite
circulation - revealing directly the process of superfluid breakdown in
Bose-Einstein condensates.