The Quantum Communication In Collective Noise Channel

Quantum information science is developing rapidly in the last20years, and hasbeen a history of several decades of years. Its two branches, quantum communicationand quantum computing, make use of the basic principles of quantum mechanics toensure the communication security and improve the computing ability. In the initialstage of development, only ideal models are discussed in theory. But with thedevelopment of the experimental research, the influence of noise on quantum systemsattracted more and more attention. The work to establish a reasonable noise model andselect an appropriate subspace which is not affected by noise to resist the negativeimpact of noise is one of the hot topics in the research of quantum communication. Inthis thesis, we introduce several methods against noises and give some quantumcommunication protocols under the collective noises.At first, using three-photon entangled state, we discussed deterministic securequantum communication (DSQC) protocol under the collective-rotation noise channel.For against the collective-rotation noise, the sender needs to prepare a series of threephoton entangled state. But the two communicators only need single-photonmeasurements. This advantage can make the protocol more convenient in practicalapplications.Second, using three-photon polarization-entangled state, we discussed controlledquantum key distribution protocol in collective-dephasing noise channel, which adoptsthe method of entanglement distribution in noise channel and measurement to obtain therandom key. But due to the existence of the controller, two security-check processes arenecessary in this protocol to ensure the safety of the communication.Then，a protocol for transmitting an unknown non-maximally entangled Bell stateare presented by using the three-photon state via collective rotation noise channel. Alice(sender) prepares a three-particle entangled state and sends two particles to Bob (thereceiver) to share an entangled quantum channel. Then performs the GHZ basismeasurement and tells Bob her measurement outcome through the classical channel.Bob needs to perform appropriate unitary transformation to realize the arbitrary unknown state transmission.Finally we discussed the error-tolerance entanglement distribution protocol byusing linear optical elements in arbitrary collective noise channel. Using the entangledrelationship of two particles, the protocol only needs the simple optical elements such aspolarization beam splitters and half wave plates rather than an auxiliary particle andCNOT gates to realize entanglement distribution without error in noise channel. Thismethod has less resource consumption, is easy to implement, and has a good prospect inthe actual quantum communication.