Preparation of single-photon states via cavity-assisted spontaneous parametric down-conversion for quantum memory based on Y7LiF4:Nd3+ crystal

We report on the realization of a tunable single-photon source compatible with quantum memories based on isotopically pure Y 7 LiF 4 crystals doped with Nd 3+ ions. The source is based on spontaneous parametric down-conversion in a PPLN crystal placed in a resonator. The latter is formed by two mirrors which are transparent for the pump (532 nm) and idler (1377 nm) fields but high reflective for the signal field (867 nm). The width of the second-order cross-correlation function between the signal and idler photons is determined to be 1.5 ns for the cavity length of 8 cm, which corresponds to a cavity bandwidth of 100 MHz.