Quantum Entanglement And Quantum Entanglement Concentration

Quantum entanglement is important for information processing and quantum computation. Quantum entanglement states, as a fundamental physical resource, are extensivelyused in quantum computation and quantum communication, quantum teleportation, andquantum dense coding, etc. In the quantum information processing the quantum channelusually must be maximally entangled. But in fact, in the real processing, storage, andtransmission of quantum states, there are inevitably all sorts of noisy channels, so themaximally entangled states usually collapse into non-maximally entangled one or evenmixed states, and the quality of entanglement is greatly degraded. Therefore, obtaining abetter entangled state from a less entangled one becomes more interesting. In this thesis,entanglement concentration of unknown non-maximally entangled states via cavity decayis studied.The thesis consists of four chapters. In chapter one we briefly review the history andresearching actuality of quantum entanglement and quantum entanglement purification,entanglement concentration.In chapter two, we introduce the basic theory of quantum entanglement. We brieflygive the simple definition of quantum entanglement. Meanwhile, we introduce servalmainly purpose of entangled states, entanglement operation, serval kinds of entangledstates and preparation of entangled states.In chapter three, we firstly introduce the scheme for concentration of entangled statesvia cavity decay. First, the methods of concentrating non-maximally entangled statesare introduced. In succession, the scheme for concentration unknown GHZ entangledstates cavity decay is proposed. Our scheme does not require a direct carrier of quantuminformation between distant atoms in which photonic states is used as a flying qubit. Jointdetection of photons leaking out of distinct cavities enables the completion of quantumconcentration.In chapter four, a summary of the work and a outlook of this aspect are given.