Theoretical Study Of Quantum Secure Direct Communication Based On Cluster State

The quantum secure direct communication(QSDC)is a novel method of quantum communication,whose major feature is the direct transmission of secret information in the quantum channel.It has high security and high capacity.Since the concept of QSDC was put forward in 2000,QSDC has been developed rapidly.Quantum entanglement plays an important role in quantum communication.According to the correlation of quantum entanglement and nocloning theorem,Based on different entangled states and different ways for quantum communication,many QSDC schemes that use are proposed.The cluster state has high connectivity and continuous entanglement.Clusters state is superior to other entangled states.It can ensure the effectiveness and correctness of quantum communication and computation.A QSDC protocol based on four-particle cluster state is proposed.It can realize 4 bit information transmission.In the protocol,a novel method is put forward to recover secret information,which converts the measurement for four-particle cluster states to two pairs of two-particle joined measurement.It can effectively reject intercept-resend attack,interception-measurement attack,entanglement-measurement attack,and so on.In the ideal case,qubit efficiency can be near 100% if the particles for detecting eavesdropping are not counted.At the same time,entanglement swaps or other complicated operations are not needed.The initial states needn't keep secrecy.Therefore,complexity of transmission process is reduced.Another QSDC protocol based on five-particle cluster state is proposed.It can realize 5 bit information transmission.A novel method is put forward to recover secret information,which convert the measurement for fiver-particle cluster states to a Bell measurement for two particles and three-particle joined measurement.At the same time,the protocol can also provide sufficient security.At last,using the correlation of four-particle cluster state,an efficient controlled QSDC protocol is proposed.In the protocol,the quantum information carrier is transmitted in blocks.All particles are used to transmit information except for particles for detecting eavesdropping.The four-particle cluster state can realize 4 bit information transmission.The protocol can also provide sufficient security.