Dynamical description of the creation and monitoring of a superposition state in a dissipative environment: the Paris experiment

Effects of dissipation during the interaction of two-level atoms with a single mode of the electromagnetic field are considered in the context of the dispersive Jaynes–Cummings model to which a damping mechanism is added. The results are applied to the analysis of the so-called Paris experiment (Brune M et al 1996 Phys. Rev. Lett. 77 4887). We obtain analytical expressions for the conditional probabilities measured in this experiment considering the dissipation during the atom–field interaction in both preparing and monitoring stages of the 'Schrodinger cat' state. We show that during the formation of the superposition state decoherence results from a competition between the atom–field (unitary) and field–cavity (dissipative) interactions. Moreover, it is quantitatively comparable to the purity loss expected for the field evolving freely during a time interval equal the interaction time. These effects are dominant at short time scales. For later times, the measured conditional probabilities reflect decoherence effects arising from field–cavity interactions.