Clock synchronization by remote detection of correlated photon pairs

In this study, we present an algorithm to detect the time and frequency differences of independent clocks based on observation of time-correlated photon pairs. This enables remote coincidence identification in entanglement-based quantum key distribution schemes without dedicated coincidence hardware, pulsed sources with a timing structure or very stable reference clocks. We discuss the method for typical operating conditions and show that the requirement for reference clock accuracy can be relaxed by about five orders of magnitude in comparison with previous schemes.