Quantum Secure Direct Communication Protocol Based on Cluster Entangled State

We present a new quantum secure direct communication protocol with three-particle entangled state. The communication parties utilize decoy photons to check eavesdropping. The sender encodes the secret message with unitary transformation, we can directly transmit secret message with Bell-basis measurement and Z-basis measurement. The protocol is efficient in that all entangled states are used to transmit the secret message and two bits message can be transmitted one time, the preparation of three-particle entangled state is realized technique, the protocol is feasible to operate. The protocol is also verified to be secure for a noise quantum channel.