Fast quantum dialogue

Quantum dialogue (QD) is a term of quantum cryptography, which can fulfill the secure exchange of two parties’ private information in an open environment. Up to now, there have been a lot of QD protocols. Many have several common components and activities, such as encoding photons coming forth with auxiliary photons and back, one party or both performing unitary operations on encoding photons, two times of security check, and both parties’ private data being decoded chronologically from encoding photons. This work proposes a brand-new QD model, whose quantum transmission is unidirectional with only one security check and decoding of both parties’ secrets are simultaneous. Equally important is neither unitary operations nor auxiliary photons being used. Consequently, such a QD can substantially reduce costs and increase efficiency, thus entitled fast quantum dialogue (FQD). The presented FQD protocol is analysed with safety and without information leakage. Moreover, its information-theoretical efficiency is 88.89%, much higher than the current maximum 66.67%. So, it offers us a better alternative for QD.