Towards quantum control of light: Shaping quantum pulses of light via coherent atomic memory

We describe a technique for generating pulses of light with controllable, well-defined photon numbers, propagation direction, timing, and pulse shapes. The technique is based on preparation of an atomic ensemble in a state with a desired number of atomic spin excitations, which is later converted into a photon pulse. Spatio-temporal control over the pulses is obtained by exploiting long-lived coherent memory for photon states and electromagnetically induced transparency in an optically dense atomic medium. Using photon counting experiments we observe collective behavior of atomic spins in a room-temperature ensemble, enabling controlled generation and shaping of few-photon sub-Poissonian light pulses. We discuss the prospects for controlled generation of n-photon Fock states.