Generation and decoherence of mesoscopic superposition states in a strongly driven micromaser

We show that the decoherence of mesoscopic superposition states of a cavity field can be observed when an additional classical field strongly drives the atoms in a micromaser like device. Due to solvable system dynamics, analytical expressions provide phase space descriptions of all stages of atom pair correlation measurements at steady-state in the presence of pumping, driving, and dissipative effects. The detection of the first atom prepares a pure field state, which entangles with the second atom that acts as a meter. The decoherence rate, derived from conditional probabilities for atomic detection, depends on the square of the interaction time, that is the parameter that rules the separation in phase space between the pure state components. The quantum coherence is unaffected by the atomic pumping. Starting instead the correlation measurement from a vacuum state and without pumping the cavity we propose an alternative method to monitor the decoherence of Schrodinger cat states.