  Robust and reliable method for reconstructing quasi-distributions of
integrated intensities of twin beams generated in spontaneous parametric
down-conversion and entangled in photon numbers is suggested. It utilizes the
first and second photocount moments and minimizes the declination from
experimental photocount histograms. Qualitatively different forms of
quasi-distributions for quantum and classical states are suggested in the
method. The transition from quantum to classical states caused by an increased
detection noise is discussed. Momentum criterion for non-classicality of twin
beams is suggested.

Quantum Physics