Entropy and entanglement of an effective two-level atom interacting with two quantized field modes in squeezed displaced fock states

We have studied the influences of ac-Stark shifts on the field quantum entr opy, with "squeezed displaced Fock states" (SDFSs) basis. By a unitary tran sformation we derive a Raman-coupled Hamiltonian perturbatively in coupling constants. The exact results are employed to perform a careful investigati on of the temporal evolution of entropy. A factorization of the initial den sity operator is assumed, with the privileged field mode being in the SDFS. We invoke the mathematical notion of maximum variation of a function to co nstruct a measure for entropy fluctuations. The results show that the effec t of the SDFS changes the quasiperiod of the field entropy evolution and en tanglement between the atom and the field. The Rabi oscillation frequency, the collapse and revival times of the atomic coherence are found to have st rikingly different photon-intensity dependent than those found previously. The general conclusions reached are illustrated by numerical results. (C) 2 001 Elsevier Science Ltd. All rights reserved.