Direct, Loss-Tolerant Characterization of Nonclassical Photon Statistics
  We experimentally investigate a method of directly characterizing the photon number distribution of nonclassical light beams that is tolerant to losses and makes use only of standard binary detectors. This is achieved in a single measurement by calibrating the detector using some small amount of prior information about the source. We demonstrate the technique on a freely propagating heralded two-photon number state created by conditional detection of a two-mode squeezed state generated by a parametric downconverter. 
Daryl Achilles, Christine Silberhorn, and Ian A. Walmsley