Entanglement between atom interacting with a thermal field of a lossless cavity and a free atom

In the present paper we studied the entanglement of a quantum system consisting of two dipole-coupled two-level atoms, one of which interacts with one-mode thermal field in a lossless cavity, and another is outside a cavity. We obtained the analytical expression of the atom-atom negativity for separable initial atomic state and investigated the influence of a detuning between the atom and the field frequencies and direct dipole-dipole interaction on an atom-atom entanglement. We derived that detuning might cause high atom-atom entanglement in the presence of the dipole-dipole interaction. We also showed that the detuning and dipole-dipole interaction are an effective mechanisms for control and operation of the atomic entanglement.