The Quantum Properties In A System Interacting Schr(?)dinger Cat State Light Field With The Atom Under Intrinsic Decoherence Condition

Quantum information science as a new object resolved the problems related to information by means of quantum theory, regarding the quantum state as the carrier of information. Quantum system is couple to its external environment all the time, because of the coherence of quantum mechanics state. It is difficult to keep the coherence of quantum state, as the quantum system is correlated with its external environment. Milburn gave a simple model of intrinsic decoherence, and made a simple modification to the standard quantum mechanics. Based on this theory, we study the quantum characteristics for the system of Schr?dinger cat state light field coherence states and a two-level atom by solving the Milburn equation. The main contents of this thesis are as following:(1) The concepts of the intrinsic decoherence, Schr?dinger cat state light field and entropy are introduced.(2)The atomic population inversion in a system of Schr?dinger cat state light field interacting with a two-level atom was studied by solving Milburn equation. The effect of intrinsic decoherence, the strength of light field and the phase angle between the two coherence states on atomic population inversion was analyzed. The results show that the atomic population inversion decreases to zero with the evolvement of time under intrinsic decoherence. The atomic population inversion damped strongly with the reducing of the intrinsic decoherence as the strength of light field is at a fixed value, and the atomic population inversion in an odd coherent state decreases quickly and the atomic population inversion in an even coherent state reduces slowly. The value of atomic population inversion in a Yurke-Stoler coherent state is between them. When the intrinsic decoherence keeps at the fixed level, the collapse and revival phenomena will be appear with the increase of the strength of light field. Rabi oscillation damped to zero faster.(3)The field entropy evolution in a system of the Schr?dinger cat state light field interacting with a two-level atom was studied by solving Milburn equation. The influences of intrinsic decoherence, the strength of light field and the phase angle between the two coherence states on the field entropy evolution was discussed. The results show that the field entropy vibration will be weak gradually because of the intrinsic decoherence, and the degree of entanglement in the field-atom system approaches to a certain value with time evolution. Furthermore, the max degree of entanglement in the field-atom system only depends on the strength of light field and the phase angle between the two coherence states, and have nothing to do with intrinsic decoherence. When the strength of light field is relatively small, the degree of entanglement is maximum in a system of a two-level atom interacting with an odd coherence state light field, and it is minimum in a system of a two-level atom interacting with an even coherence state light field; it is intermediate for a system of a two-level atom interacting with Yurke-Stoler coherence state light field. When the intrinsic decoherence is fixed and the strength of light field is relatively large, the degree of entanglement in the field-atom system existing in the Yurke-stoler, the even coherence state and odd coherence state tend to the same.