An investigation of entanglement and quasiprobability distribution in a generalized Jaynes-Cummings model

In this paper, we consider a unified approach to study the degree of entanglement of two-level systems interacting with a quantized electromagnetic field. We investigate a range of parameters in a generalized Jaynes-Cummings model (JC-model) with intensity-dependent, field nonlinearity and nonresonant coupling. In terms of the density matrix and without the diagonal approximation we derive an explicit expression for the entanglement degree using a function analogous to mutual entropy. This notion is inspired by the fact that the quantum state may be interpreted as a measure of information. With the aid of the quasiprobability distribution function, the statistical properties of the field are analyzed. It is shown that when the atom is initially in its upper-level and the one-photon at resonance, the Q-function splits into two peaks and counter rotate in phase space. © 2003 American Institute of Physics.