Effects Of Microwave Field On Squeezing And Entanglement Of The Probe Field In QED System

Abstract：Quantum optics is a subject to investigate the quantum characters of thelight field and the interaction between quantum field and atoms. Squeezing andentanglement are the most important quantum features of light field. The preparationand transmission of the squeezing and entanglement are needed in quantumcommunication and quantum computation. Cavity QED has been used in different fieldswidely, because it can suppresses the decoherence induced by the environment. Usually,the bad cavities are used to prepare the squeezed or entanglement field due to its simpleoutput. Here we shall focus on the preparation of two-mode entangled fields, and thesqueezing of the single-mode squeezed field transit from EIT medium. We organize thisthesis as follows:In chapter1, we have reviewed the development of the EIT phenomenon, quantumsqueezing and quantum entanglement.In chapter2, the theories that studying the interaction between the fields and theatoms have been introduced by using semi-classical and quantum means, respectively.In chapter3, we have reviewed the basic theory of cavity QED，which includes theJaynes-Cummings model and cavity input-output theory.In chapter4, we introduce the basic theory of entanglement and squeezing, such astheir definitions and classifications.In chapter5, the two-mode squeezing and entanglement of the output fields aregenerated by using an three-level closed-loop atom interacting with two mode of thecavity. From the squeezing spectrum, we find that the width of the squeezing(entanglement) spectrum is sensitive to the cavity decay rate, however we can changethe effective coupling constants and the microwave field to modulate it. The depth ofthe squeezing or entanglement spectrum is dependent on the microwave field. This can be useful in realizing the controllable quantum communication.In chapter6, we investigate the squeezing of a squeezed vacuum as a probe fieldafter propagating through a collection of-type atoms of which the ground states aredriven by a microwave. It is found that by adjusting the microwave field the degree ofthe squeezing can be enhanced, and their frequency regions become wider. In particular,the squeezing from a shot noise can be produced by adjusting the microwave field. Thiscan also be useful in the controllable quantum communication.