Optimal quantum storage of broadband single photons

Summary form only given. The authors present a theoretical analysis of a quantum memory which shows how to efficiently transfer an ultrashort single photon wavepacket to a long-lived collective excitation of an ensemble of absorbers with the well-known three level Lambda-structure, by application of an ancillary control field. We describe a general prescription for optimizing the efficiency of the storage process for arbitrary detunings, and then we show how the dynamics simplify in the off-resonant limit. In this case spontaneous emission losses are eliminated and the interaction becomes unitary; being characterized by a universal mode decomposition.