Theory of noise suppression in {\Lambda}-type quantum memories by means   of a cavity
  Quantum memories, capable of storing single photons or other quantum states of light, to be retrieved on-demand, offer a route to large-scale quantum information processing with light. A promising class of memories is based on far-off-resonant Raman absorption in ensembles of $\Lambda$-type atoms. However at room temperature these systems exhibit unwanted four-wave mixing, which is prohibitive for applications at the single-photon level. Here we show how this noise can be suppressed by placing the storage medium inside a moderate-finesse optical cavity, thereby removing the main roadblock hindering this approach to quantum memory. 
J. Nunn, S. Thomas, J.H.D. Munns, K.T. Kaczmarek, C. Qiu, A. Feizpour,   E. Poem, B. Brecht, D.J. Saunders, P.M. Ledingham, ...
quant-ph