Deterministic Secure Four-qubit GHZ States Three-step Protocol for Quantum Communication

A deterministic secret quantum communication (DSQC) protocol is proposed with four-qubit GHZ states. It has some outstanding advantages. Firstly, it has a high communication capacity as each four-qubit GHZ state can carry three bits of secret messages. Secondly, as all of the quantum resource is useful, the intrinsic efficiency of the communication approaches the maximum value 100 % . Besides, its total efficiency of the present protocol is 60 % , more higher than most of the current existing DSQC protocols. The decoy photon detection technique guarantees that Eve’s any eavesdropping behavior can be detected on site, and the three-step transmitting strategy ensures no information will be leaked in the communication process. Moreover, the present protocol is feasible with the present day technique.