Study On Quantum Properties In The System Of Atom Interacting With Light Field Via Intensity-dependent Coupling

It is one of the important contents for the quantumn optics to study of the dynamics and non-classical properties of the atom interacting with the field. Theory of quantum entropy is the theoretical foundation and it is a powerful tool in understanding and studing the hot issues of quantum computing, quantum communication, quantum entanglement etc. In this paper, the quantum properties of entanglement, atomic compression and fidelity etc. in a model of field interacting with an atom via intensity-dependent coupling are studied by using quantum entropy theory, and a series of significant results are obtained.1. In the process of a two-mode coherent state field interacting with an atom via intensity-dependent coupling, the evolution of entanglement between the atom and field is investigated by using quantum reduced entropy. The results show that the EPR state and the separable state between the field and atom can be prepared periodically in the high field conditions(the average photon number of the field is very large), by choosing the system parameters of the initial state, or controlling the action time between the atom and fielsd.2. In the process of a two-mode coherent state field interacting with an atom via intensity-dependent coupling, the evolution of entanglement the two-mode field is investigated by using relative entropy respectively. It is shown that it can be regulated by choosing the initial state parameters of the atom and field. The entanglement of the two-mode field will increase or decrease, but it's impossible to disentangle completely. The results show that the system of a two-mode coherent state field interacting with an atom is a good entanglement resource, when it is counted intensity-dependent coupling.3. From a quantum information point of vie preparation and control of the atomic optimal entropy squeezing state(AOEST) are researched for the system of a moving two-level atom entanglement with the field under the intensity-dependent coupling; its results with those of atomic squeezing based on the Heisenberg uncertainty relation is compared; sufficient and necessary conditions of preparation of the AOEST is analyzed and numerical verification of the AOEST is done. The influences of the field-mode structure parameter on the AOEST is examined. It is shown that information entropy squeezing is a remarkable precision measure for the atomic squeezing. The AOEST can be prepared by controlling the time of the atom interaction with the field cutting the entanglement bewteen the atom and field choosing coherence of the atom and modulating relative phase the systems. A lasting AOEST can be obtained by controlling the field-mode structure parameter.4. Fidelity of quantum information in the system of a moving two-level atom entanglement with the field under the intensity-dependent coupling is researched, by using quantum entropy theory. And the evolution of quantum state fidelity of the system is discussed, which in different atomic initial state, in different field mode structure parameter, and in different average photon number of conditions. Meanwhile, the relationship between the fidelity and the entanglement of atom and field is studied . It is shown that the fidelity of quantum states is affected in the conditions of different atomic initial state, different field mode structure parameter, or different average photon number. Field mode structure parameter value leads to the disentanglement between atom and the field, and more, it leads to a significant increase in fidelity of quantum state. In the whole process, the fidelity of atom is significantly higher than the fidelity of the system or optical field, atom fidelity performance is reflected better in quantum information transmission process.