The Theory Of Entanglement Concentration And Nondemolition Analysis For Multi-bit Quantum Entanglement States

Quantum information is a new subject,which is consists of Quantum Mechanics and Quantum Information.Until now,there have been a great development in the quantum information both in theory and experiment.Quantum entanglement plays an important role in quantum information progress,especially the completely distinguished quantum states and the maximally entanglement states.As we all known,the quantum entanglement would be affected by the noises caused by the environment during the transmission.As a result,it makes the maximally entanglement into a pure less-entangled state even a mixed state.Hence the efficiency of quantum communication decrease sharply.There are several methods which have been proposed for distilling the less-entangled state into the maximally entangled state such as entanglement distillation,entanglement concentration,entanglement purification and so on.With the development of the quantum information,the research work focus on the entangled state analysis and entanglement concentration.The thesis is organized as follow:In Chapter 1,the concept of entangled states and hyperentangled states are first introduced.Next,some operation for entangled states are briefly introduced,which consists of nondemoleted analysis,entanglement concentration and entanglement purification.Finally,several common optical elements and cross-Kerr nonlinearity are introduced.In Chapter 2,the scheme of hyperentanglement-assisted multi-photon Greenberger-Horne-Zeilinger(GHZ)states analysis with cross-Kerr nonlinearity is proposed.It is showed that the scheme not only can nondemoleted distinguish the two-photon Bell states and three-photon GHZ states,but also can distinguish N-photon GHZ state,completely.In Chapter 3,the scheme of efficient distillating a maximally hyperentanglement W states from arbitrary less-hyperenanglement multi-photon W states with linear optics is proposed.The scheme is first completed the hyperentanglement concentration for W states.As well as we showed that the scheme is also distilling a maximally N-photon hyperentangled W states from a less one.In Chapter 4,the scheme of single-photon-assisted entanglement concentration for an arbitrary entangled photon pair with the diamond nitrogen-vacancy center insides cavity is proposed.With the special properties of the nitrogen vacancy center(NV-center),it can be repeated the process of entanglement concentration at a higher success probability.Meanwhile,the protocol is more suitable for multiphoton system concentration.At last,we discuss the NV-center and demonstrate that it can be realized by the current technology.Finally,the conclusion and the outlook are given in the end of paper.