Analysis Of Problems Related To Controlled Quantum Teleportation

Entanglement is an important resource in quantum information processing,which plays an important role in areas like quantum secret sharing,quantum dense coding,quantum key distribution,quantum secure direct communication,and quantum computing.In quantum teleportation,the acquisition of entanglement is particularly challenging and meaningful because entanglement allows two parties far apart,namely the sender Alice and the receiver Bob,to transmit unknown quantum states by sharing the maximally entangled state without actually transmitting the physical system.Quantum teleportation methods are used in large-scale quantum networks and distributed quantum computing.Quantum controlled teleportation was proposed by Karlsson and Bourennane in 1998.Unlike conventional quantum teleportation,quantum controlled teleportation transmits arbitrary unknown quantum states from the sender to the receiver only with the permission of the controller.Controller’s privileges are realized by limiting access to measurement information of controller.In this paper,we mainly study quantum controlled teleportation,present some controlled teleportation schemes and analyze them.In the first chapter,we first review some basic quantum theories,including the theorem that the unknown quantum states cannot be cloned,the basic assumptions of quantum mechanics,quantum bit,quantum logic gates,and quantum entangled states.Then we introduce the traditional quantum teleportation scheme,including the basic knowledge,background and operation process of the scheme.In chapter 2,we propose a new quantum controlled teleportation protocol for any number of users.First,the initial entangled state of the system consisting of n+2 qubits is allocated between the sender,the controller,and n users.During each transmission,the sender decides which user is the recipient of the state transmitted.The recipient can recover the state transmitted with the cooperation of other users.It is extended to the case of transporting multiparticle quantum states.Then,we propose a quantum controlled teleportation scheme using multiple maximally-entangled Bell states as quantum channels to transmit N particle entangled states.We compare and analyze this two schemes from the aspects of operation strength and difficulty,the consumption of quantum and classical resources.The protocols have many applications such as quantum networks,cloud computing and quantum cryptography.In chapter 3,we propose a bidirectional controlled teleportation scheme.Firstly,a manyto-one quantum controlled teleportation scheme is presented.In this scheme,N transmitters transmit the unknown quantum states in their hands to the receiver Bob under the control of Charlie,the controller.Then we present an improved bidirectional quantum controlled teleportation protocol.More specifically,under the control of Charlie,Alice transmits the entangled state in her hand to Bob,while Bob also transmits another quantum state to Alice.That is,Alice and Bob are both sender and receiver.To achieve this goal,a specific quantum entangled state is required to be shared as a quantum channel between Alice,Bob and Charlie.We then extend this to the case where Alice and Bob transmit multiple quantum states simultaneously under the control of a controller.The multiple quantum states transmitted can be single-particle quantum states or multi-particle quantum states.In chapter 4,the idea of bidirectional controlled teleportation is extended,and a general framework for the study of ring controlled teleportation is proposed.Under Charlie’s control,each party transfers her qubit state to a nearby qubit through shared entanglement,local unitary operations,and classical communication.We take three transporters as an example to concretely describe this process and prove that the framework is feasible.Then the proposed scheme is compared and analyzed with the existing schemes,and the superiority of the proposed scheme is pointed out.In chapter 5,we propose a multi-objective shared high-dimensional quantum controlled teleportation scheme using high-dimensional entangled states as the quantum channels.The scheme proposed in chapter 2 is further extended to three-dimensional,four-dimensional and ddimensional cases.A high-dimensional bidirectional quantum controlled teleportation scheme is presented using the high-dimensional maximally entangled state as a quantum channel.Alice,Bob and Charlie must share the entangled states which are used to construct quantum channels.According to the distribution mode of entangled particles and the different selection of measurement basis,the communication parties Alice and Bob can respectively transmit their own high-dimensional quantum states to each other with a certain probability under the supervision of the controller.Based on this basis,we present a high-dimensional loop controlled quantum teleportation scheme.All the schemes proposed by us only use Bell base measurement and single particle measurement,which are physically easy to implement.In chapter 6,based on the definition of controlling force in quantum controlled teleportation,we evaluate the performance of the controlled teleportation protocols we presented in this paper.