Experimental observation of spatial antibunching of photons
  We report an interference experiment that shows transverse spatial antibunching of photons. Using collinear parametric down-conversion in a Young-type fourth-order interference setup we show interference patterns that violate the classical Schwarz inequality and should not exist at all in a classical description. 
W. A. T. Nogueira, S. P. Walborn, S. Padua and C. H. Monken