Theoretical Research On Quantum Information Remote Transmission Via Partially Entangled States

As a new cross-field discipline,quantum information science combines quantum mechanics and information science.Non-locality and quantum superposition theoretically guarantee the high security and efficiency in quantum information processing.Quantum information science has recently attracted world-wide emphasis and greatly developed for its advantages compared to classical information technology.Quantum state transmission is one of the most rapidly developing research subjects of quantum information science,and is absolutely necessary for remote quantum communications and quantum computation in future.Quantum state transmission has important significance in basic theory research and practical applications.In the study of quantum information transmission theory based on entanglement,to overcome the decoherence induced by surrounding environment and improve the efficiency of quantum state transmission is important.In addition,to meet the demands of wide-area quantum communications,high-security and high-success-probability quantum state transmission is of crucial importance in quantum relay network.Taking these problems into consideration,based on the non-maximally entanglement,wide-area quantum communication networks are discussed here,meanwhile,secure and efficient quantum teleportation network communication protocols and remote state preparation protocols are studied in this dissertation.The main results are as follows.1.A quantum communication network which contains two-layer database and satellite entanglement distribution is constructed.To solve the problems existing in some present quantum teleportation networks,such as security flaws,low success probability of quantum state transmission,a high-security and high-success-probability protocol is presented for the quantum teleportation network.An arbitrary quantum state can be transferred from one node to another in the wide-area quantum network.Entanglement swapping of Bell-like states is utilized to establish the end-to-end quantum channel,improving the security of quantum state transmission.Auxiliary qubit and specific unitary operations are introduced to recover the target quantum state,increasing the success probability.Performance analysis shows that the proposed protocol has advantages in security and efficiency of quantum states transmission.2.A resource-conserving protocol is proposed for the controlled teleportation of an arbitrary single-qubit.Aiming at the disadvantages of some present controlled teleportation schemes,such as loss of control power,high entanglement degree of the quantum channel,restricted target qubits,a quantum logic circuit is constructed to obtain a set of particular three-particle partially entangled states.Using these states as the quantum channel,a novel controlled teleportation protocol is proposed.It is made clear through the theoretical analysis that arbitrary single-qubit states can be teleported in the proposed protocol,unit teleportation fidelity and 100% success probability can be achieved.Meanwhile,as long as quantum channel's entanglement degree equals to or greater than 3/4,the controller's power can be guaranteed.Quantum entanglement resource is conserved therefore.3.Two deterministic controlled remote state prepararion(CRSP)schemes independent of the quantum channel's entanglement degree are proposed for single-and two-qubit states preparation.Novel four-particle partially entangled state is utilized to construct the preshared quantum channel,participants perform specific projective measurements and unitary operations instead of phase-shift operations,thus improving the success probability of state preparation.In the proposed CRSP protocol,phase-shift operation is not needed,the sender can always transmit quantum state information to the receiver with unit success probability,irrespective of the channel's entanglement degree.4.Two non-recursive and deterministic joint remote state preparation(JRSP)schemes are proposed for single-and two-qubit states preparation.A quantum logical circuit is constructed to obtain the ingenious four-particle partially entangled states,which are used as the pre-shared quantum channel.A set of complete orthogonal bases are proposed for the senders' projective measurements,with the cooperation of receiver's unitary operations,joint remote preparation of arbitrary single-and two-qubit states can be realized with 100%success probability,which is independent of the channel's entanglement degree.During the process of quantum states preparation,auxiliary qubits and recursive channel modulations are not needed,thus improving the efficiency of JRSP.