Nonclassical measure of cavity held interacting with thermal reservoir

The time variation of the nonclassical measure of the cavity field interact ing with a thermal reservoir is examined. From the knowledge of the quasi-p robability distribution function of the cavity field as a function of time, the nonclassical measure of the state is explicitly calculated in terms of the initial nonclassical measure, the decay constant, and the average numb er of photons in the reservoir. The nonclassical measure of the sub-Poisson ian character is also considered and it is confirmed that the sub-Poissonia n character, for an initial Fock state, disappears in half the time require d for the cavity field to become classical. (C) 2001 Published by Elsevier Science B.V.