We present an algorithm to detect the time and frequency difference 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 in reference clock accuracy can be relaxed by about 5 orders of magnitude in comparison with previous schemes.
@article{arxiv.0901.3203,
title = {Clock synchronization by remote detection of correlated photon pairs},
author = {Caleb Ho and Antia Lamas-Linares and Christian Kurtsiefer},
journal= {arXiv preprint arXiv:0901.3203},
year = {2009}
}