A Bidirectional Quantum Secure Direct Communication Protocol Based on Five-Particle Cluster State

To transmit a message safely, five-particle cluster state particles are used to construct a bidirectional quantum secure direct communication protocol. Five-particle cluster state particles are used for both detecting eavesdroppers and transmitting secret messages. All of the five-particle cluster states' photons for detection are mixed to the sending sequence to detect eavesdroppers. The detection rate approaches 88% per qubit. The five-particle cluster states needed are only one fifth of the photons in the sending sequence. In this protocol, there is no photon carrying secret information transmitting in quantum channel, and the classical XOR operation which serves as a one-time-pad is used to ensure the security of the protocol. Compared with three photons of each five-particle cluster state as detection photons, the five photons in this study will decrease the five-particle cluster states needed for detection greatly.