Experimental superradiance and slow-light effects for quantum memories

The effects of high optical depth phenomena, such as superradiance, are investigated in potential quantum memory materials. The results may have relevance for several schemes, including controlled reversible inhomogeneous broadening, atomic frequency combs, and quantum memories based on electromagnetically induced transparency, which are based on using ensembles as storage media. It is shown that strong superradiant effects manifested as decay rates larger than 1/T*(2) are present even for moderate values of alpha L <= 5 and increases as a function of alpha L. For even higher alpha L, effects such as off-resonant slow light is demonstrated and discussed and, finally, the efficiency of time-reversed optimized input pulses is tested. A maximum retrieval efficiency of similar to 20% is reached and agreement with the theoretically expected result is discussed.