Preparation and Decoherence of Two-Atom Entangled States in a Dissipative Cavity

We present a scheme for generating four pairs of two-atom Einstein--Podolsky--Rosen (EPR) states using the simultaneous interaction of the two atoms with a single-mode cavity field under a large detuning condition. The influence of cavity dissipation on the prepared EPR states is investigated by means of the superoperator method and the state fidelity. It is shown that some kinds of the prepared EPR states are robust against cavity dissipation and the intensity of the field, and maintain their entanglement invariance, and the others are fragile and completely destroyed by the action of cavity dissipation and the intensity of the field in the long-time limit. Decoherence time of the fragile entangled states is extremely small for a typical cavity-QED experimental data.