We demonstrate a point-to-point clock synchronization protocol based on bidirectionally exchanging photons produced in spontaneous parametric down conversion (SPDC). The technique exploits tight timing correlations between photon pairs to achieve a precision of 51ps in 100s with count rates of order 200s−1. The protocol is distance independent, secure against symmetric delay attacks and provides a natural complement to techniques based on Global Navigation Satellite Systems (GNSS). The protocol works with mobile parties and can be augmented to provide authentication of the timing signal via a Bell inequality check.
@article{arxiv.1812.08450,
title = {Symmetrical clock synchronization with time-correlated photon pairs},
author = {Jianwei Lee and Lijiong Shen and Alessandro Cerè and James Troupe and Antia Lamas-Linares and Christian Kurtsiefer},
journal= {arXiv preprint arXiv:1812.08450},
year = {2019}
}