Deterministic quantum secure direct communication and authentication protocol based on W-class state

A Quantum secure direct communication (QSDC) and authentication protocol based on the W-class state is presented to enhance the efficiency of eavesdropping detection. In this protocol, the W-class state is used to transmission the checking sequence and detect eavesdroppers. In the security analysis, the method of entropy theory is introduced, and two detection strategies are compared quantitatively by using the constraint between the information that eavesdroppers can obtain and a normalized difference parameter is introduced. To obtain the same amount of information, the eavesdropper must face a higher detection probability in the proposed protocol than in the comparison. The security of the proposed protocol is also discussed. The analysis results indicate that the proposed protocol is more secure, but it must send more particles.