Study Of Quantum Communication And Quantum Cryptography

Quantum information is a crossed subject from quantum physics and information science. Because of the superior advantage and the bright future, quantum information has attracted more and more attention and developed a lot.Quantum information is combined of quantum communication and quantum computation. What quantum computation concern are quantum computer and quantum algorithm suitable for quantum computer. The main parts of quantum communication are quantum cryptography, quantum teleportation, long-distance quantum communication and so on. Quantum information is derived from quantum physics, while it also develops quantum physics. The content of the thesis is about the research of two kinds of quantum cryptography and a necessary technique for quantum repeater. Also the thesis shows the result of our experiment about the contradiction between quantum physics and local reality theory.In order to solve the attenuation and decoherence problem of long-distance quantum communication, the technique of quantum repeater appeared. To realize a quantum repeater, synchronization of independent entangled photon sources is needed. To split a single pump laser pulse in N beams and distribute them to each segment will cause the number of the synchronized entangled photon pairs exponentially decrease with the number of segments. We synchronized entangled photon source pumped by two independent Ti:sapphire lasers using passive synchronization technique. At the same time, we measured the CHSH inequality and proved strictly that quantum...