Theoretical Study On Generation Of Continuous Variable Entanglement In Coupled Cavity QED

Quantum entanglement is one of the most striking features of quantum mechanics. It is a critical factor in marking the boundary between classical and quantum world, which has been recognized an important resource in quantum computation and information. The preparation of continuous variable (CV) entanglement is an advanced subject in the field of quantum information and quantum optics, since CV quantum communication has its potential advantages such as high bit transmission rates and big communication band. Cavity QED system has excellent anti-decoherence since the lifetime of atom and photon is larger than their interaction time in cavity, which has been proved to be an excellent quantum device to produce entanglement. Furthermore, the scale of generating entanglement state is from microcosmic to mesoscopic and even macroscopic progressively in cavity QED system.In this thesis, based on cavity QED, the generation of CV entanglement and quantum nondemolition measurement of entangled atomic ensembles in coupled cavity system are in-vestigated theoretically. Employing quantum master equations and the algebraic approach, we propose a theoretical scheme to generate CV entanglement by using the atomic nonlinear-ity in coupled cavity. The atom driven by classical laser induces the entanglement between the two cavity fields. The coupled cavity system containing atoms can not only produce entanglement, but also execute quantum nondemolition measurement of entangled atomic ensembles. We study coupled cavity system filled with atoms, and show that the entangle-ment evolution of both the atomic ensembles and cavity fields are of the same periods, so quantum nondemolition measurement of entangled atomic ensembles can be realized theo-retically. Furthermore, we also present schemes to generate entanglement in coupled cavity optomechanical systems including atoms or optical parametric amplifiers, and discuss the effect of nonlinearity of the atoms or optical parametric amplifiers on the generation of CV entanglement of coupled cavity optomechanical systems.The research in this thesis is helpful for understanding the quantum effects in coupled cavity, so it has some positive effect and certain reference value on the research of the nonlinear optical system for precision measurement by the coupled cavity column used in the research of quantum information.