Months-long real-time generation of a time scale based on an optical clock

Abstract

Time scales consistently provide precise time stamps and time intervals by combining atomic frequency standards with a reliable local oscillator. Optical frequency standards, however, have not been applied to the generation of time scales, although they provide superb accuracy and stability these days. Here, by steering an oscillator frequency based on the intermittent operation of a 87Sr optical lattice clock, we realized an “optically steered” time scale TA(Sr) that was continuously generated for half a year. The resultant time scale was as stable as International Atomic Time (TAI) with its accuracy at the 10−16 level. We also compared the time scale with TT(BIPM16). TT(BIPM) is computed in deferred time each January based on a weighted average of the evaluations of the frequency of TAI using primary and secondary frequency standards. The variation of the time difference TA(Sr) – TT(BIPM16) was 0.79 ns after 5 months, suggesting the compatibility of using optical clocks for time scale generation. The steady signal also demonstrated the capability to evaluate one-month mean scale intervals of TAI over all six months with comparable uncertainties to those of primary frequency standards (PFSs).

Towards the optical second: verifying optical clocks at the SI limit

“…Following convention, here we treat the type B uncertainties of the PSFS ensemble's constituent standards as uncorrelated between standards, enabling a PSFS type B uncertainty of 1.3 × 10 −16 , lower than the uncertainty of any individual fountain. We measure a value of ν Yb = 518 295 836 590 863.71 (11) Hz, which represents a fractional frequency difference of (2.1 ± 2.1) × 10 −16 from the 2017 BIPM recommended value of the Yb frequency [16]. The reduced-chi-squared statistic, χ 2 red , is 0.98, indicating that the scatter in the eight monthly values is consistent with the stated uncertainties.…”

New bounds on dark matter coupling from a global network of optical atomic clocks

“…Our network is composed of optical lattice atomic clocks located at the National Institute of Standards and Technology (NIST), Boulder, CO, USA ( 23 , 24 ), at LNE-SYRTE (Laboratoire National de Métrologie et d’Essais, Systèmes de Références Temps-Espace), Paris, France ( 25 , 26 ), at KL FAMO (Krajowe Laboratorium Fizyki Atomowej, Molekularnej i Optycznej), Torun, Poland ( 27 , 28 ), and at the National Institute of Information and Communications Technology (NICT), Tokyo, Japan (see Fig. 1 ) ( 29 , 30 ). Each clock uses an optical cavity–stabilized laser that is frequency tuned to resonantly interrogate the atomic clock transition of cold atoms trapped in an optical lattice.…”

Multi-node optical frequency dissemination with post automatic phase correction

“…The proposed technique considerably simplifies future efforts to make coherent optical frequency signals available to many users, enabling the above mentioned applications, and paving a path towards a redefinition of the unit of time, the SI second through regular and practical international comparisons of optical clocks [34], [37], [38], [39], [40].…”