Quantum dialogue protocol with high information density

The invention creates a quantum dialogue protocol for encoding two classical bits by using one quantum bit, compared with a protocol for encoding one classical bit by using one quantum bit in the prior art, the quantum dialogue protocol has higher quantum communication efficiency, and the protocol consists of a quantum communication participant A and a quantum communication participant B; the two parties use two-degree-of-freedom photons, namely photons with polarization degree of freedom and empty mode degree of freedom, as information carriers, a bait photon technology is used for providing security guarantee for quantum dialogue, the purpose of secret information exchange of the two parties is finally achieved, analysis shows that the risk of information leakage does not exist in the quantum dialogue, and the safety of the quantum dialogue is improved. The theoretical information efficiency of the quantum dialogue protocol is 83.33%, and compared with an existing quantum dialogue protocol of the same type,