Direct measurement and reconstruction of nonclassical features of twin   beams generated in spontaneous parametric down-conversion
  Correlations in twin beams composed of many photon pairs are studied using an intensified CCD camera. Joint signal-idler photon-number distribution and quantum phase-space quasi-distributions determined from experimental data have nonclassical features. 
Ondrej Haderka, Jan Perina Jr, Martin Hamar, Jan Perina