Programmable atom-photon quantum interface
  We present the implementation of a programmable atom-photon quantum interface, employing a single trapped $^{40}$Ca$^+$ ion and single photons. Depending on its mode of operation, the interface serves as a bi-directional atom-photon quantum-state converter, as a source of entangled atom-photon states, or as a quantum frequency converter of single photons. The interface lends itself particularly to interfacing ions with single or entangled photons in hybrid quantum networks. 
Christoph Kurz, Pascal Eich, Michael Schug, Philipp M\"uller, J\"urgen   Eschner
quant-ph