Progress on optical-clock-based time scale at NIST: Simulations and preliminary real-data analysis

Yao, Jian; Sherman, Jeffrey A.; Fortier, Tara M.; Leopardi, Holly; Parker, T.E.; Levine, Judah; Savory, J.; Römisch, Stefania; McGrew, William F.; Zhang, Xiaogang; Nicolodi, Daniele; Fasano, R.; Schäffer, Stefan A.; Beloy, K.; Ludlow, Andrew D.

doi:10.1002/navi.248

Cited by 8 publications

(7 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A Kalman filter is used to estimate the frequency and frequency drift of the free-running time scale AT1 with respect to the Yb clock, and AT1 is steered based on this estimate [19,43]. Here, we summarize the algorithm employed.…”

Section: Appendix B: Kalman-filter Steering Algorithm For Optical-clomentioning

confidence: 99%

Optical-Clock-Based Time Scale

et al. 2019

Self Cite

View full text Add to dashboard Cite

A time scale is a procedure for accurately and continuously marking the passage of time. It is exemplified by Coordinated Universal Time (UTC), and provides the backbone for critical navigation tools such as the Global Positioning System (GPS). Present time scales employ microwave atomic clocks, whose attributes can be combined and averaged in a manner such that the composite is more stable, accurate, and reliable than the output of any individual clock. Over the past decade, clocks operating at optical frequencies have been introduced which are orders of magnitude more stable than any microwave clock. However, in spite of their great potential, these optical clocks cannot be operated continuously, which makes their use in a time scale problematic. In this paper, we report the development of a hybrid microwave-optical time scale, which only requires the optical clock to run intermittently while relying upon the ensemble of microwave clocks to serve as the flywheel oscillator. The benefit of using clock ensemble as the flywheel oscillator, instead of a single clock, can be understood by the Dick-effect limit. This time scale demonstrates for the first time sub-nanosecond accuracy for a few months, attaining a fractional frequency stability of 1.45×10 −16 at 30 days and reaching the 10 −17 decade at 50 days, with respect to UTC. This time scale significantly improves the accuracy in timekeeping and could change the existing time-scale architectures.

show abstract

Section: Appendix B: Kalman-filter Steering Algorithm For Optical-clomentioning

confidence: 99%

Optical-Clock-Based Time Scale

et al. 2019

Self Cite

View full text Add to dashboard Cite

show abstract

“…For example, a recent demonstration of two ytterbium optical lattice clocks at NIST found instability, systematic uncertainty, and reproducibility at the 1 × 10 −18 level or better, thus outperforming the current realization of the second by a factor of >100 [7]. The superior performance of optical clocks motivates current exploratory work aimed at incorporating optical frequency standards into existing time scales [8][9][10][11][12][13]. Furthermore, for the first time, the gravitational sensitivity of these clocks surpasses state-of-the-art geodetic techniques and promises to find application in the nascent field of chronometric leveling [14].…”

Section: Introductionmentioning

confidence: 99%

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

McGrew

Zhang

Leopardi

et al. 2019

Optica

119

110

View full text Add to dashboard Cite

The pursuit of ever more precise measures of time and frequency is likely to lead to the eventual redefinition of the second in terms of an optical atomic transition. To ensure continuity with the current definition, based on a microwave transition between hyperfine levels in ground-state 133 Cs, it is necessary to measure the absolute frequency of candidate standards, which is done by comparing against a primary cesium reference. A key verification of this process can be achieved by performing a loop closure-comparing frequency ratios derived from absolute frequency measurements against ratios determined from direct optical comparisons. We measure the 1 S 0 → 3 P 0 transition of 171 Yb by comparing the clock frequency to an international frequency standard with the aid of a maser ensemble serving as a flywheel oscillator. Our measurements consist of 79 separate runs spanning eight months, and we determine the absolute frequency to be 518 295 836 590 863.71(11) Hz, the uncertainty of which is equivalent to a fractional frequency of 2.1 × 10 −16 .This absolute frequency measurement, the most accurate reported for any transition, allows us to close the Cs-Yb-Sr-Cs frequency measurement loop at an uncertainty of <3×10 −16 , limited by the current realization of the SI second. We use these measurements to tighten the constraints on variation of the electron-to-proton mass ratio, µ = m e /m p . Incorporating our measurements with the entire record of Yb and Sr absolute frequency measurements, we infer a coupling coefficient to gravitational potential of k µ = (−1.9 ± 9.4) × 10 −7 and a drift with respect to time oḟ µ µ = (5.3 ± 6.5) × 10 −17 /yr. arXiv:1811.05885v1 [physics.atom-ph]

show abstract

“…NIST proposed to steer an ensemble of clocks instead of a single maser to the Yb optical lattice clock and showed a time scale with sub-nanosecond accuracy compared to UTC over a few months, and a fractional frequency stability of 8.8 × 10 −17 at 50 days. They used the Kalman filter algorithm and steered frequency parameters after each optical lattice clock operation [10,18,19]. Furthermore, there has been a report of generating a time scale based entirely on optical technology [20].…”

Section: Introductionmentioning

confidence: 99%

Preliminary study of generating a local time scale with NIM ⁸⁷Sr optical lattice clock

Zhu¹,

Lin²,

Wang³

et al. 2022

Metrologia

View full text Add to dashboard Cite

A local time scale can be generated by steering flywheel clocks with state-of-the-art optical lattice clocks. This paper presents our simulations about the influence of the optical lattice clock’s operational strategies and the flywheel clock’s noise characteristics on the performance of the generated time scale. By post-processing the measured frequency difference between the optical lattice clock Sr1 and the hydrogen maser HM50 at the National Institute of Metrology (NIM), during the modified Julian dates (MJD) 59029-59059, a local time scale with 0.68 ns time variation referencing to the TT(BIPM20) is demonstrated.

show abstract

Progress on optical-clock-based time scale at NIST: Simulations and preliminary real-data analysis

Cited by 8 publications

References 11 publications

Optical-Clock-Based Time Scale

Optical-Clock-Based Time Scale

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

Preliminary study of generating a local time scale with NIM ⁸⁷Sr optical lattice clock

Contact Info

Product

Resources

About

Progress on optical-clock-based time scale at NIST: Simulations and preliminary real-data analysis

Cited by 8 publications

References 11 publications

Optical-Clock-Based Time Scale

Optical-Clock-Based Time Scale

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

Preliminary study of generating a local time scale with NIM 87Sr optical lattice clock

Contact Info

Product

Resources

About

Preliminary study of generating a local time scale with NIM ⁸⁷Sr optical lattice clock