The Theory Of Entanglement Concentration For Multi-bit Entanglement States And Hyperentanglement States

In recent years,quantum information science gained a number of achievements in theory and achieved a major breakthrough in experiment.Quantum information science is an interdisciplinary of quantum mechanics and modern information,and the entanglement is the foundation of quantum information science.Entanglement is an important resource in quantum information communication,most protocols in quantum information require the different parties to share entanglement.In practical transmission or the process for storing an entangled states,the entangled states is unable to avoid interacting with their environment.This decoherence has led to a decrease in entanglement of the entangtled photon pairs,the initial states of entangtled photon pairs are become non-maximally entangled states.Most of quantum information protocols can be realized with maximally entangled states,the decrease of entanglement will make quantum cnmmunication protocols insecure or decrease the fidelity of teleportation.A theoretical issue in the science of quantum information is how to distill the non-maximally entangled states which influenced by channel noises and imperfect sources,and restore the non-maximally entangled states back to maximally entanglement.The entanglement concentration as a way to distill the non-maximally entangled states,therefore,we propose three entanglement concentration protocols.This paper mainly study how to entanglement concentrate the multi-bit entanglement and hyperentanglement of the entangtled photon pairs.This article arranged as follows way:In Chapter 1,the concept of the entanglement,the method of entanglement concentration and entanglement purification,optical devices and the optical property of the quantum-dot spins inside one-side optical microcavities are introduced.The major research subjects and the organization of the dissertation are given at the end of this chapter.In Chapter 2,inspired of the weak cross-Kerr nonlinearity,the entanglement concentration protocol for partially entangled cluster states is proposed with two-step operations.By iteracting the entanglement concentration process,we can improve the success probability of the obtained maximally entangled cluster states based on the results of the numerical simulation.Now that the new proposed protocol extends to concentrate multiparticle non-maximally entangled states.In Chapter 3,the entanglement concentration protocol of concentrating the arbitary non-maximally hyperentangled Greenberger-Home-Zeilinger(GHZ)states is proposed with the cross-Kerr nonlinearity used in Chapter 2.Likewise,by iteracting the the entanglement concentration process,we can improve the success probability of the obtained maximally entangled GHZ states.Numerical simulation shows that the success probability of the entanglement concentration protocol not only about the number of iteration but it is about parameters of initial state.In Chapter 4,we show how to use the optical property of the quantum-dot spins inside one-side optical microcavities to build two quantum-nondemolition detectors(QND).The entanglement concentration protocol of concentrating the arbitary non-maximally hyperentangled W states is proposed based on the QNDs.Moreover,the present protocol is also suitable for the partially entangled multi-photon W states concentration.Finally,the conclusion has made the summary and research forecast.