Entropy behaviors and statistical properties of the field interacting with a Ξ-type three-level atom

In this paper the entropy behaviors of the field interacting with a Ξ-type three-level atom, are studied and the formulas for calculating the field (atom) entropy are derived. With the help of the quasiprobability distribution function Q, the statistical properties of the field are analyzed. It is shown that the Q function splits into three peaks where two peaks counterrotate in phase space when the atom is initially in upper-level 3 and the one photon detunes Δ=0. The Schrödinger-cat state is produced at t=12TR (TR is the revival time in one-photon processes) as the atom initially in middle-level 2.