Three-Party Simultaneous Quantum Secure Communication Based on Closed Transmission Loops

A kind of novel three-party quantum secure direct communication protocol is proposed with the correlation of two-particle entangled state. In this scheme the qubit transmission forms a closed loop and every one of the three participants is both a receiver and a sender of particle sequences in the bidirectional quantum channels. Each party implements the corresponding unitary operations according to its secret bit value over the quantum channels and then extracts the other two parties’ unitary operations by performing Bell measurements on the encoded particles. Thus they can obtain the secret information simultaneously. Finally, the security analysis shows that the present three-party scheme is a secure protocol.