DESCRIPTION OF THE INFLUENCE OF A RESERVOIR VIA COARSE-GRAINING IN PHASE-SPACE

We show that the Q-function of a single-mode field which is attenuated or amplified by a phase-sensitive environment can be expressed throug h a coarse-grained Q-function with time-dependent coarse-graining para meters. This fact can be utilized for simulation of the decay of quant um systems into various environments. In particular, we have derived a n analytical expression describing the time-evolution of the Q-functio n of the initial Fock state which decays into a phase-sensitive reserv oir.