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We study the system of a single qubit couples to a single mode thermal field according to a multi-photon Jaynes?Cummings-type interaction with phase decoherence. Both the time evolving entanglement and the stationary state entanglement are calculated by adopting the log-negativity as a measure. It is found that the multi-photon process can enhance the stationary state entanglement of this system and can enlarge the range of the parameter ?/g and the mean photon number of initial thermal field in which the stationary state is distillable.

We adopt a dynamical algebraic approach to study the system of a two-level atom moving in a quantized travelling light field and a gravitational field with a multiphoton interaction. The exact solution of the system is obtained and used to discuss the influence of the gravitational field on the collapses and revivals of atomic population, sub-Poissonian statistics.

We investigate the system, which consists of two two-level atoms confined in a linear trap which has been surrounded by an optical cavity, with the Milburn model of intrinsic decoherence, and find an explicit analytical solution of the Milburn equation. The entanglement between the two atoms is then calculated by making use of concurrence. The influence of intrinsic decoherence on the entanglement is also discussed.

The modified Jaynes-Cummings model of a single two-level atom placed in the common domain of two cavities or interacting with two quantized modes is studied by a dynamical algebraic method. With the help of an SU(2) algebraic structure, we then obtain the eigenvalues, eigenstates, time evolution operator and atomic inversion operator for the system. We managed to investigate the modified Jaynes-Cummings model governed by the Milburn equation and present the exact solution of the Milburn equation. PACS: 42. 50. -p, 32. 80. -t, 02. 20. -a, 03. 65. Fd

As a non-adiabatic generalization of a recent work of Gerry, the manifestation of the Aharonov-Anandan phase in the degenerate parametric amplifier of quantum optics is discussed by making use of the Lewis-Riesenfeld quantum theory. We find the Lewis invariant for the system and study its evolution. The Aharonov-Anandan phase is then calculated and the connection between the Aharonov-Anandan phase difference and the average photon-number of the output field is obtained. Finally, the observable effect of the phase difference is investigated.

Some examples of a new kind of the Aharonov-Anandan phase which is of mechanical origin are studied. It is the non-adiabatic generalization of the mechanical Berry phase. We first study the periodic motion and then the interference effect. Finally we discuss the relation between Aharonov-Anandan phase and Berry phase.

We investigate the quantum discord dynamics in a cavity quantum electrodynamics system, which consists of two noninteracting two-level atoms driven by independent optical fields and classical fields, and find that the quantum discord vanishes only asymptotically although entanglement disappears suddenly during the time evolution in the absence of classical fields. It is shown that the amount of quantum discord can be increased by adjusting the classical driving fields because the increasing degree of the amount of quantum mutual information is greater than classical correlation by applying the classical driving fields. Finally, the influence of the classical driving field on the fidelity of the system is also examined.

We investigate the quantum discord dynamics of two effective two-level atoms independently interacting with two quantized field modes through a Raman interaction in the presence of phase decoherence. The influence of the phase decoherence and detuning on the evolution of the quantum discord and entanglement between two atoms is discussed. It is found that the quantum discord is more robust than the entanglement under the phase decoherence, and the amount of discord and entanglement between two atoms can be increased by adjusting the detuning.

We investigate the entanglement swapping of continuous variable using the pair coherent state as the input state and the two-mode squeezed vacuum which is exposed in a phase decoherence environment as the quantum channel. By adopting the log-negativity as the measure of entanglement, we analyze how entanglement of the two initial states and the phase decoherence environment affect the entanglement swapping quality.

On the basis of the generalized invariant formulation,the invariant related unitary transformation method is used to study the evolution of the quantum Dirac field in a time dependent spatially homogeneous electric field.We solve the functional Schrdinger equation for the Dirac field and obtain the exact solutions and corresponding total phase.The total phase includes both the dynamical phase and geometric phase (Aharonov Anandan phase).

The invariant-related unitary transformation method is used to study the transference of a kind of nonclassical properties between two interacting modes of light.With the aid of numerical computation,it is interesting to find that the mutual conversion of the Fock states (being nonclassical) and the coherent states is attained when the interaction is chosen appropriately.