In 1998, we succeeded in reducing the light speed to 17 m/s by creating a laser induced quantum interference in a Bose-Einstein condensate (BEC). The low light speeds are obtained in an optical medium created from entangled states between Bose condensed atoms and a laser field. The intensity of this light field controls the optical properties for another, pulsed laser beam sent through the medium. The reported reduction of the pulse propagation speed by a factor of 20 million is associated with a spatial compression of the laser pulses in the condensate by the same factor. Furthermore, the established quantum interference allows for lossless, shape preserving transmission of light pulses through atomic media that would otherwise be totally opaque.

For more, see our ultra-slow light paper here.

Soon after, we succeeded in stopping a light pulse completely in an atomic cloud cooled to a temperature just above the transition temperature for BEC. At the time when the light pulse is slowed, compressed, and contained within the atomic sample, we turn off the control laser field abruptly and then turn it back on at a later time. When the control laser is turned back on, the light pulse is regenerated: we can stop and controllably regenerate the light pulse. During the storage time, thermal motion and associated smearing of the optical information imprinted in the atoms are minimized with the use of ultracold atoms.

For more, see our stopped light paper here.

We have used slow and stopped light in Bose-Einstein condensates for generation of quantum shock waves in superfluids, for optical processing, and for creation of a pulsed atom laser.