Preparation And Manipulation Of Multi-particle Entanglement

Preparation and manipulation of quantum entangled states lies at the heart of the quantum information. First, entangled states are important resources for quantum communication and quantum computation such as quantum teleportation, quantum one-way computation and so on. The process of performing quantum information tasks even can be regarded as the process of manipulation of entangled states. Second, they play a crucial role in testing the foundmental principles of quantum mechanics. This thesis is mainly about preparation of the multiparticle entangled states and test of the conflict between quantum mechanics and local realism. In this thesis we propose schemes for generation of multiparticle entangled states and report the experimental realization of six-photon entangled states and the experimental test of the nonlocality of quantum mechanics based on the four-photon mixed state.The thesis is structured as follows:Chapter No. 1 is the exordium. We simply introduce the main content of quantum information theory and elaborate notion, separability and measure of entanglement.In chapter No.2, we firstly introduce some basic technique of quantum optics, including spontaneous parametric down conversion and some optical elements, then, we propose schemes for preparation of five-photon graph states, lastly, we report the experimental realization of six-photon entangled states.In chapter No. 3, we introduce resonant and nonresonant interactions beween the atoms and cavities in cavity electrodynamics and propose schemes for generating five-atom graph states via cavity electrodynamics.In chapter No.4, we firstly introduce Bell's theory, CHSH inequality and GHZ contradiction, and then, we report the experimental test of all-verus-nothing violation of local realism based on the four-photon mixed state.Chapter No.5 is conclusion and future outlook.