Deterministic and Storable Single-Photon Source Based on a Quantum Memory

A single-photon source is realized with a cold atomic ensemble (${}^{87}\mathrm{Rb}$ atoms). A single excitation, written in an atomic quantum memory by Raman scattering of a laser pulse, is retrieved deterministically as a single photon at a predetermined time. It is shown that the production rate of single photons can be enhanced considerably by a feedback circuit while the single-photon quality is conserved. Such a single-photon source is well suited for future large-scale realization of quantum communication and linear optical quantum computation.