The Quantum Properties In A System Interacting Schr(?)dinger Cat State Light-field With Atomic Bose-Einstein Condensate

The problem concerned with the interaction between optical field and atoms in a system has been a very important subject in the field of quantum optics. For better disclosing the quantum properties in the system of atom interacting with field, strengthening the content of the traditional quantum optics, and better understanding and developing the quantum information theory itself .In this paper, by means of the complete quantum theory and begin with the Hamiltonian of the field interacting with the atom, the quantum properties are discussed in the system of the Bose-Einstein condensate atom interacting with the Schr(o|¨)dinger Cat states field. The main content of this thesis are as follows:In the first chapter, the Bose-Einstein condensate, the squeezing theory, and the entropy theory, and the fidelity theory and the theories on quantum entanglement and the method in quantum entanglement measurement are briefly introduced.In chapter two, the squeezing properties of the Schr(o|¨)dinger Cat states field interacting with Bose-Einstein condensate of two-level atom are studied by means of quantum theory. The results show that the optical field and the atomic laser of even coherent state and odd coherent state interacting with Bose-Einstein condensate appear no squeezing effects, whereas the optical fields and the atomic laser of Yurke-Stoler coherent state show squeezing effects. The intensity of the initial light field and values of the coupling constant have the influences on the squeezing properties of the field and atomic laser.In chapter three, the time evolution property of the atomic information entropy squeezing in Bose-Einstein condensate atom interacting with the Schr(o|¨)dinger cat-states are studied by means of quantum theory. The results indicate that when phase angleφis atπ/2between the two coherent states in the Schr(o|¨)dinger cat state, atomic information entropy squeezing will shows squeezing effects alternately with the variation of the intensity of optical field and coupling coefficients.In chapter four , the evolution characteristics of quantum state fidelity in an interacting system of S-cat state optical field and Bose-Einstein condensate have been studied by means of quantum fidelity and the influence of the light field intensity and interaction among atoms of Bose-Einstein condensate on the quantum state fidelity have been discussed. The results indicate that the optical field can modulate the fidelities of quantum states in the system of interaction, whereas the interaction constantsΩamong atoms influence mainly the oscillation frequency of the fidelity of quantum state of system.In chapter five, the characteristics of field entropy evolution in an interacting system of optical filed and atomic Bose-Einstein condensate have been studied by means of quantum theory. Under the condition of resonance, the entanglement of field-atom are investigated using the quantum reduced entropy .The influences of the initial intensity of filed and the interaction intensity between optical field and atoms and among BEC'S atoms on the evolution of the entanglement degree of filed-atom are discussed. Optical field intensity and parameters of system affect the entanglement degree and the periodicity of the evolution of field entropy. In case of weak the interaction among atoms ,when selecting proper the interaction intensity between light field and BECs? atoms and optical field intensity , entanglement between Schr(o|¨)dinger cat state and BEC,s atoms can be kept further extent.