Influence of the Stark shift and Kerr-like medium on the evolution of field entropy and entanglement in two-photon processes

We have investigated the evolution of the field quantum entropy and the ent anglement of the atom-field in the two-photon process, taking into account the level shifts produced by Stark effect with an additional Kerr-like medi um for one mode. The exact results are employed to perform a careful invest igation of the temporal evolution of the entropy. A factorization of the in itial density operator is assumed, with the privileged field mode being in a coherent state. We invoke the mathematical notion of maximum variation of a function to construct a measure for entropy fluctuations. The effect of both the Stark shift and the presence of a Kerr-like medium on the entropy is analyzed. It is shown that the addition of the Kerr medium and the Stark shift has an important effect on the properties of the entropy and entangl ement. The results show that, the effect of the Kerr medium and the Stack s hift changes the quasiperiod of the field entropy evolution and entanglemen t between the atom and the field. The general conclusions reached are illus trated by numerical results.