Time gating of heralded single photons for atomic memories

We demonstrate a method for time gating the standard heralded continuous- wave (cw) spontaneous parametric down-converted (SPDC) single photon source by using pulsed pumping of the optical parametric oscillator (OPO) below threshold. The narrow bandwidth, high purity, high spectral brightness and the pseudo-deterministic character make the source highly suitable for light-atom interfaces with atomic memories.