Entanglement between two qubits one of which interacts with a thermal field

Abstract: In this paper, we have investigated the entanglement between two dipole coupled two-level atoms. The model, in which only one atom is trapped in an lossless cavity and interacts with single-mode thermal field, and the other one can be spatially moved freely outside the cavity has been carried out. We have considered the effect of the atomic coherence on the entanglement behavior. We have shown that a thermal field might cause high entanglement between the atoms both for coherent and incoherent initial atomic states only for small values of the cavity mean photon number. In the considered model the atoms would get entangled even when both atoms are initially in the excited state. We have also derived that the degree of entanglement is weakly dependent on the strength of dipole-dipole interaction for coherent initial states.