QUANTUM COHERENCE IN A DISSIPATIVE-DRIVEN SYSTEM AND THE OPTICAL STERN-GERLACH EXPERIMENT

The quantum coherence of a single mode electromagnetic field in a cavi ty is analysed when a linear pumping is considered together with the d amping mechanism of the cavity, An expression for the decoherence time of the field is estimated and it turns out to be independent of the p umping process, An interesting situation occurs in the long time limit when the action of the pumping is shown to induce a finite degree of quantum coherence in the stationary state of the field. For specific v alues of the parameters involved in the problem this state is very clo se to a coherent state and is considered in the realization of the opt ical Stem-Gerlach experiment. Other particular cases are also investig ated.