<p>A quantum memory scheme with a frequency conversion interface has been proposed, where the processes of storage/retrieval of photons in a resonant polyatomic ensemble and single-photon frequency conversion in a nonlinear medium are combined in a single cavity. Compared to independent quantum memory and frequency converter, the proposed approach allows one to avoid unnecessary losses during radiation input/output and to completely overcome the need to match the operating wavelengths and bands of two devices. A solution of the Heisenberg–Langevin equations that describes the cycle of storage followed by retrieval of a single-photon wave packet has been obtained and used to formulate the conditions for achieving a high quantum memory efficiency, in particular, modified impedance matching conditions.</p>