Optimal Storage and Retrieval of Single-Photon Waveforms
  We report an experimental demonstration of optimal storage and retrieval of heralded single-photon wave packets using electromagnetically induced transparency (EIT) in cold atoms at a high optical depth. We obtain an optimal storage efficiency of (49+/-3)% for single-photon waveforms with a temporal likeness of 96%. Our result brings the EIT quantum light-matter interface close to practical quantum information applications. 
Shuyu Zhou, Shanchao Zhang, Chang Liu, J. F. Chen, Jianming Wen, M. M.   T. Loy, G. K. L. Wong, and Shengwang Du
quant-ph