Quantum Secure Direct Communication Based on Partially Entangled States

A new three-party quantum secure direct communication protocol with authentication is proposed. The advantage of the scheme is that through authentication one can confirm the sender´s legitimate identity, partially entangled states used as information carrier are easy to prepare and store, there is no need to transmit quantum states with secret message in quantum channel and two users can simultaneously communicate with the third party. In ideal channel, the protocol is secure against incoherent attack.