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First Demonstration of nonlocal two-way quantum clock synchronization on fiber link

Hou Feiyan, Dong Ruifang, Runai Quan, Xiao Xiang, Tao Liu, Shougang Zhang

Published Jan 1, 2018• 1 citation
Publisher

Abstract

We have demonstrated a two-way quantum clock synchronization by using frequency entangled pulses. For two clocks separated by 20km fiber, a timing stability of 0.85ps was achieved at averaging time of 5120s with a synchronization accuracy of 10ps.
DOI
10.1364/cleopr.2018.th4j.3

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Based on the second-order quantum interference between frequency entangled photons that are generated by parametric down conversion, a quantum strategic algorithm for synchronizing two spatially separated clocks has been recently presented. In the reference frame of a Hong-Ou-Mandel (HOM) interferometer, photon correlations are used to define simultaneous events. Once the HOM interferometer is balanced by use of an adjustable optical delay in one arm, arrival times of simulta- neously generated photons are recorded by each clock. The clock offset is determined by correlation measurement of the recorded arrival times. Utilizing this algorithm, we demonstrate a proof-of-principle experiment for synchronizing two clocks separated by 4 km fiber link. A minimum timing stability of 0.44 ps at averaging time of 16000 s is achieved with an absolute time accuracy of 73.2 ps. The timing stability is verified to be limited by the correlation measurement device and ideally can be better than 10 fs. Such results shine a light to the application of quantum clock synchronization in the real high-accuracy timing system.