Figure 1: QPQ Protocol (IMAGE) Science China Press Caption The interference wiring diagram of the newly proposed QPQ protocol, where the database generates a single-photon signal with N optical pulses and shifts the phase of each pulse randomly by 0 or π, then the user extracts the phase differential of two pulses of them by the circuits on the right side and a random number r. Credit ©science china press Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.