Theoretical Research On The Entanglement Dynamics And The Quantum Teleportation Under The Influence Of Pauli And Depolarizing Noises

Quantum entanglement is a kind of important resource in the field of quantuminformation, this resource is extremely fragile. The real quantum system can’t beisolated from the surrounding environment, so the influence of quantum noise mustbe considered on the entanglement of the quantum system. Quantum noise willcause the decay of quantum entanglement and even sudden death, and will have aninfluence on quantum information processing. So it is necessary to study theevolution of entanglement of quantum system in different quantum noisyenvironments.Strong theoretical support will be provided for maintianing maximum exist inthe quantum information processing by controlling the evolution of theentanglement of a quantum system and understanding the quantum noise of quantumentanglement evolution of the system, which is an important part of the applicationof quantum information technology. At the same time, the entangled mixed stateswhich are generated by the factors such as quantum noise will play a leading role inthe process of actual quantum information processing. So the study on theentanglement evolution characteristics of entangled mixed states under the quantumnoise has an important practical significance in the application of quantuminformation technology.This dissertation is concerned with the research on the entanglement suddendeath phenomenon in the quantum information and gives a class of controlledentanglement evolution model of a two atomic quantum system. The points areemphasized that the entanglement evolution characteristics of two types of specialtwo particle entangled mixed states in quantum information under local independent(or local collective) Pauli and depolarizing noisy environments. The theory ofquantum teleportation is especially analyzed when the quantum channel is affectedby the quantum noisy environment.The main research content of this paper is as follows:The entanglement dynamics of two atoms within a cavity is studied. TheConcurrence and Negativity of two atoms are discussed when we choose the twodifferent three atomic W states which can not be transformed by local operation andclassical communication as the initial state of atoms and different particles numbersstates as the initial cavity field state. It is also analyzed about the reasons for theappearance of entanglement sudden death. The results showed that atomic initialstate and the initial cavity photon number had important effect on the appearance ofsudden death phenomenon. The next study is the entanglement dynamics of two types of special twoparticles entangled mixed states in local independent (or local collective) Pauli anddepolarizing quantum noisy environments. One type of two particle entanglement isthe mixed entangled state between the Bell state and the|00(or|11) state, and theother one is the extended Werner-like state. For each type of quantum systems, theanalytical expressions of the density matrix under different noisy environments aregiven by the quantum master equation method. And for every quantum noisyenvironment, the variation of Concurrence with various parameters under localindependent and local collective environments is given. The comparative analysis iscarried on the Concurrence of both cases, evaluating the effects the mixture ratio orthe purity of quantum systems on the entanglement evolution, and analyzing thereasons which result in entanglement sudden death and entanglement preserved. It isfound that there is a specific area where the entanglement degrees of quantumsystem could be maintained in the initial values under some local collective Paulinoisy environments.The theory of quantum teleportation is studied when the quantum channel isaffected by different Pauli and depolarizing quantum noisy environments. Combinedwith the quantum teleportation of quantum circuit model, the fidelity and theaverage fidelity of quantum teleportation are given when the quantum channel (withone of four different Bell states as quantum channel) is subjected local independent(or local collective) Pauli and depolarizing quantum noisy environments. For eachnoisy environment, a comparative analysis of the average fidelity is made underlocal independent and local collective environment. The results show that only oneof the four Bell states is suitable as the quantum channel when the quantum channelis affected by different Pauli and depolarizing noisy environments.This dissertation can benefit the further understanding about the reasons whichcaused entanglement sudden death and will provides certain theory reference inactual quantum communications in order to maintain the entanglement maximum. Itwill also offer some theoretical basis to obtain the quantum teleportation with ahigher average fidelity.