  A single photon source is realized with a cold atomic ensemble ($^{87}$Rb
atoms). In the experiment, single photons, which is initially stored in an
atomic quantum memory generated by Raman scattering of a laser pulse, can be
emitted deterministically at a time-delay in control. It is shown that
production rate of single photons can be enhanced by a feedback circuit
considerably while the single-photon quality is conserved. Thus our present
single-photon source is well suitable for future large-scale realization of
quantum communication and linear optical quantum computation.
