Purification of single-photon entanglement with linear optics
  We show that single-photon entangled states of the form |0>|1>+|1>|0> can be purified with a simple linear-optics based protocol, which is eminently feasible with current technology. Besides its conceptual interest, this result is relevant for attractive quantum repeater protocols. 
Nicolas Sangouard, Christoph Simon, Thomas Coudreau, and Nicolas Gisin