Generation Of Entangled Coherent States Based On Cavity QED

Born as a new cross subject of information science and quantum mechanics, quantum information is undoubtedly a fruitful production of quantum mechanics. Meanwhile, it widely enriches the research field of quantum mechanics and greatly promotes the development of quantum theory. Due to the differences between quantum mechanics and classical mechanics, quantum information takes a new look and shows some distinguished advantages compared with classical information. Quantum entangled states, as a fundamental physical resource for quantum information processing, are extensively used in quantum computation and quantum communication, quantum teleportation, quantum dense coding, and so on. In recent years, the preparation of continuous variable entanglement and its application in quantum optics and quantum information are acting on a frontier field. As continuous variable entanglement, entangled coherent states attract more and more attentions of people. This paper introduced and summarized the progress in entangled coherent states, and also proposed a scheme to generate entangled coherent states based on cavity QED system.This dissertation consists of three chapters. In the first chapter, some basic theories of quantum information and cavity QED are introduced, including quantum qubit and quantum decoherence, where, the quantum theory about the interaction between atoms and field is emphasized in detail. In the second chapter, we show the definition of entangled states, several mainly measurements of entangled degree and several kinds of entangled states. On this basis, we discuss the definition of the entangled coherent states and its measurements. In the last chapter, which is our main work, we first present two schemes to generate entangled coherent states by considering a two-mode cavity field interacting with a two-level atom and a three-level atom, respectively. Then a new method is proposed to prepare two modes of cavity in an entangled coherent state based on the nonresonant interaction of a three-level A -type atom with two cavity modes and two classical fields. The influence of the cavity loses is also discussed.