The Investigation Of Quantum Entanglement Sharing

Quantum information is a discipline formed by many subjects like quantummechanics, information science and cryptography and so on. It opens up a new way tothe development of communication technology and computer science. Quantum stateworks as information carrier of quantum information, which researching thetransmission and processing of information, in order to achieve safer communicationand more efficient computation. Among all the fields of quantum informationprocessing, quantum entanglement is undoubtedly one of the most important researchobject. Quantum entanglement is a unique phenomenon in the quantum world, withoutcounterpart in the classical world. At the same time it is the core resource of quantuminformation processing, which has been widely used in quantum communication andquantum computation.Among all the candidate systems of quantum communication, photon is consideredas the most promising one. Thanks to such characteristics as high-speed of transmission,facility of transport, and simplicity of manipulation, photon is considered to be an idealentity of quantum communication. In most quantum communication schemes based onquantum entanglement, participators need to share a pair of maximally entangledphoton, with photon polarization degree of freedom as the information carrier. However,the polarization degree of freedom of photon is easily influenced by the environmentnoise.The entangled photon pairs will inevitably interact with the environment duringthe transmission and then decoherence will affect the purity and the entanglement,which subsequently affect the efficiency and security of quantum communicationscheme. Many solutions were proposed to solve this problem, such as quantum errorcorrecting codes, quantum error avoiding transmission, purification of entanglement,entanglement concentration etc. In this thesis, we also investigated the subject of remoteentanglement sharing under noise conditions, and put forward the correspondingsolutions. Firstly, we proposed a hyperconcentration scheme based on projectionmeasurement. Hyperentanglement is a new resource for quantum informationprocessing, which entangled in more than one degree of freedom simultaneously. Itcan carry more information and has good application prospect in quantum informationprocessing. The scheme we proposed considering both the polarization and spatialfreedom hyperentanglement has a very important significance on remote entangled state sharing. In addition, we also proposed a noise channel multi-particle polarizationentanglement distribution scheme. In most existent quantum communication schemespeople discussed the sharing of Bell state and GHZ state. There were a few schemesabout the W state. The W state is also an important quantum resource, which has veryimportant application in quantum communication. Therefore, in this paper, we putforward a W states entanglement distribution scheme,in which the parties involved inthe communication can share the W state deterministically with100%fidelity.Compared with the existing schemes against channel noise, our two schemes considerednew entangled states and the most commonly used two degrees of freedom of photon,which have great theoretical significance and application prospect.