Nonadiabatic approach to quantum optical information storage - art. no. 043809

We show that there is no need for adiabatic passage in the storage and retr ieval of information in the optically thick vapor of Lambda-type atoms. Thi s information can be mapped into and retrieved out of long-lived atomic coh erence with nearly perfect efficiency by strong writing and reading pulses with steep rising and falling edges. We elucidate similarities and differen ces between the "adiabatic" and "instant" light storage techniques, and con clude that for any switching time, an almost perfect information storage is possible if the group velocity of the signal pulse is much less than the s peed of light in the vacuum c and the bandwidth of the signal pulse is much less then the width of the two-photon resonance. The maximum loss of the i nformation appears in the case of instantaneous switching of the writing an d reading fields compared with adiabatic switching, and is determined by th e ratio of the initial group velocity of the signal pulse in the medium and speed of light in the vacuum c, which can be very small. Quantum restricti ons to the storage efficiency are also discussed.