Quantum Information Investigation For Atom Interacting With Field

Content: 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, this paper introduces the entropy theory, the entanglement theory, and the fidelity theory of the quantum information theory to the system of atom interacting with field, taking advantage of computation, data processing, demonstration, and comparison etc.First, the computation of entropy in the system of atom interacting with field is investigated. If the state in the system of atom interacting with field is pure, the Von Neumann entropy of the field based on the trait values of the field's density matrix quantifies the field's quantum information truly.Second, the field entropy property in the system of the cascade three-level atom interacting with the exited coherent state is discussed. The field entropy is oscillatory and more than zero at any times except for the start moment. Parameters α and m have effects on the field entropy. With the increasing of α or m, the regular pattern of the field entropy evolution is more obvious, and the field entropy curve is regulated by the "carrier wave" whose period turns to be longer with the increasing of α or m . The field entropy is more susceptible to changes in α than in m .Third, the entanglement in the system of the two-level atom interacting with the finite dimension mixed-field is studied. The entanglement of formation and the Peres condition have good correspondence, and if the mixed-state deviates the similar pure state slightly, its maximum entanglement drops suddenly. The conclusion of the entanglement of the infinite dimension mixed-state in J-C model never losing is demonstrated besides finding the necessary condition of disentanglement of the finite dimension mixed-state in J-C model.Fourth, the fidelity of quantum information for the cascade three-level atom interacting with the excited coherent state is discussed. Field parameters and detuning parameters have negligible effects on the average values of the quantum information fidelity, and the system fidelity not only is minimum but also presents its comprehension to the fidelity of field and atom. The coherent fidelity of field is regulative in the whole system while average photo numbers, excited times and detuning parameters have obvious effects on the frequency of fidelity evolution.