Engineering single atom and single photon sources from entangled atomic   ensembles
  We discuss the application of dipole blockade techniques for the preparation of single atom and single photon sources. A deterministic protocol is given for loading a single atom in an optical trap as well as ejecting a controlled number of atoms in a desired direction. A single photon source with an optically controlled beam-like emission pattern is described. 
M. Saffman and T. G. Walker