Universal Approach to Optimal Photon Storage in Atomic Media
  We present a universal physical picture for describing storage and retrieval of photon wave packets in a Lambda-type atomic medium. This physical picture encompasses a variety of different approaches to pulse storage ranging from adiabatic reduction of the photon group velocity and pulse-propagation control via off-resonant Raman fields to photon-echo based techniques. Furthermore, we derive an optimal control strategy for storage and retrieval of a photon wave packet of any given shape. All these approaches, when optimized, yield identical maximum efficiencies, which only depend on the optical depth of the medium. 
Alexey V. Gorshkov, Axel Andre, Michael Fleischhauer, Anders S.   Sorensen, Mikhail D. Lukin