Sub-Poisson States Heralded at a Hong-Ou-Mandel Interference Peak
  A peak in coincidence events has been observed in a modified Hong-Ou-Mandel interferometer fed with weak coherent states inside the region of overlapping wave-packets. The inversion of the usual interference pattern represented by the HOM dip is equally observed when the wave packets are frequency displaced. The higher rate of coincidences indicates that photons are more likely to take on different output paths of the interferometer. This effect was harnessed so a detection on one of the arms could herald the presence of a photon in the other. The second order autocorrelation function at zero time was experimentally determined by means of the Hanburry-Brown and Twiss experiment and its value below 1 confirmed the sub-Poisson photon statistics of the heralded states. 
G. C. Amaral, F. Calliari, T. Ferreira da Silva, G. P. Tempor\~ao, and   J. P. von der Weid
quant-ph