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Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE

Optical direct comparison of87Sr optical lattice clocks using a >50 km telecommunication fiber link

Hidekazu Hachisu, Atsushi Yamaguchi, Miho Fujieda, Motohiro Kumagai, Shigeo Nagano, Ying Li, T. Ido, T. Takano, Masao Takamoto, Hidetoshi Katori

Published Sep 8, 2011• 1 citation
Publisher

Abstract

An 87Sr-based-optical lattice clock in NICT is compared to that of The University of Tokyo using a >50 km fiber link. In this work, we have demonstrated for the first time that two distant Sr lattice clocks generate the same frequency with systematic uncertainty of 0.31 Hz (7.3 × 10-16 fractionally) for the 429 THz clock frequency.
DOI
10.1117/12.893357

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Direct Comparison of Distant Optical Lattice Clocks at the 10−1610^{-16}10−16 Uncertainty
Fiber-based remote comparison of 87 Sr lattice clocks in 24 km distant laboratories is demonstrated. The instability of the comparison reaches 5 × 10 -16 over an averaging time of 1000 s, which is two orders of magnitude shorter than that of conventional satellite links and is limited by the instabilities of the optical clocks. By correcting the systematic shifts that are predominated by the differential gravitational redshift, the residual fractional difference is found to be (1.0±7.3) × 10 -16 , confirming the coincidence between the two clocks. The accurate and speedy comparison of distant optical clocks paves the way for a future optical redefinition of the second.