Entanglement in a system of a three-level atom interacting with a single-mode field in the presence of arbitrary forms of the nonlinearity and of the atomic initial state

The interaction of a three-level atom in the V-configuration with a single-mode field under the mechanism of a multi-photon transition is studied. Influences of different possible choices of the atomic initial state, the mean photon number, the nonlinearity of the Kerr-like medium and the detuning parameters within various forms of the intensity-dependent atom–field couplings on the von Neumann entropy are analyzed. Simple analytical expressions of the unitary time evolution and density operators in the context of the framework of the dressed states are derived. General conclusions reached are illustrated by numerical results. (paper)