Heralding Single Photons from Pulsed Parametric Down-Conversion
  We describe an experiment in which photon pairs from a pulsed parametric down-conversion source were coupled into single-mode fibers. Detecting one of the photons heralded the presence of the other photon in its fiber with a probability of 83%. The heralded photons were then used in a simple multi-photon interference experiment to illustrate their potential for quantum information applications. 
T.B. Pittman, B.C Jacobs, and J.D. Franson