“…If it is positive, as for instance in the case of propagation of radiation through random media, the uncertainty of the photon statistics is greater than that of the Poisson statistics corresponding to the coherent state [17,18] . If it is negative the anticorrelation (antibunching) of photons may occur as in optical parametric processes [10,11,19] and in Raman and hyper-Raman scattering [20][21][22][23] . Note that, in the latter case, the average over the initial gaussian statistics of the field leads to a deviation of the actual statistics from the shifted gaussian statistics .…”