Atomic time-keeping from 1955 to the present

Guinot, B.; Arias, E. F.

doi:10.1088/0026-1394/42/3/s04

Cited by 53 publications

(44 citation statements)

References 24 publications

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“…Finally, we conclude by considering atomic clocks which operate at the very highest optical frequencies and beyond. (Guinot and Arias, 2005). They are the result of worldwide cooperation of about 70 national metrology laboratories and astronomical observatories that operate atomic clocks of different kinds.…”

Section: Applications and Future Prospectsmentioning

confidence: 99%

Optical atomic clocks

et al. 2015

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Optical atomic clocks represent the state of the art in the frontier of modern measurement science. In this article a detailed review on the development of optical atomic clocks that are based on trapped single ions and many neutral atoms is provided. Important technical ingredients for optical clocks are discussed and measurement precision and systematic uncertainty associated with some of the best clocks to date are presented. An outlook on the exciting prospect for clock applications is given in conclusion.

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Section: Applications and Future Prospectsmentioning

confidence: 99%

Optical atomic clocks

et al. 2015

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“…The development of atomic timekeeping is nicely described in the SI Brochure Appendix 2 (Practical realization of the definition of the unit of time; http://www.bipm.org/ en/publications/mises-en-pratique/; BIPM-Bureau International des Poids et Mesures) as well as in the review papers from Guinot (2011), Arias (2005, and Guinot and Arias (2005). The unit of time is the SI second, which is based on the value of the caesium ground-state hyperfine transition frequency, as adopted by the 13th Conférence Générale de Poids et Mesures (CGPM) in 1967 (Terrien 1968).…”

Section: Terrestrial Time and The Realization Of International Timescmentioning

confidence: 99%

“…The computation of the relativistic redshift is regularly re-evaluated to account for progress in the knowledge of the gravity potential and in the standards, see, for example, Weiss (2003, 2017) for such work on frequency standards at NIST (National Institute of Standards and Technology), Boulder, Colorado, USA (United States of America), or Calonico et al (2007) for similar activities for the Italian metrology institute INRIM (Istituto Nazionale di Ricerca Metrologica), Torino. More information on time metrology, the general relativity framework, and international timescales (especially TAI) is given in the review papers by Guinot (2011), Guinot and Arias (2005), Arias (2005), and Petit et al (2014).…”

Section: Introductionmentioning

confidence: 99%

Geodetic methods to determine the relativistic redshift at the level of 10 $$^{-18}$$ - 18 in the context of international timescales: a review and practical results

Denker

Timmen

Voigt

et al. 2017

J Geod

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The frequency stability and uncertainty of the latest generation of optical atomic clocks is now approaching the one part in 10 18 level. Comparisons between earthbound clocks at rest must account for the relativistic redshift of the clock frequencies, which is proportional to the corresponding gravity (gravitational plus centrifugal) potential difference. For contributions to international timescales, the relativistic redshift correction must be computed with respect to a conventional zero potential value in order to be consistent with the definition of Terrestrial Time. To benefit fully from the uncertainty of the optical clocks, the gravity potential must be determined with an accuracy of about 0.1 m 2 s −2 , equivalent to about 0.01 m in height. This contribution focuses on the static part of the gravity field, assuming that temporal variations are accounted for separately by appropriate reductions. Two geodetic approaches are investigated for the derivation of gravity potential values: geometric levelling and the Global Navigation Satellite Systems (GNSS)/geoid approach. Geometric levelling gives potential differences with millimetre uncertainty over shorter distances (several kilometres), but is susceptible to systematic errors at the decimetre level over large distances. The GNSS/geoid approach gives absolute gravity potential values, but with an uncertainty corresponding to about 2 cm in height. For large distances, the GNSS/geoid approach should therefore be better than geometric levelling. This is demonstrated by the results from practical investigations related to three clock sites in Germany and one in France. The estimated uncertainty for the relativistic redshift correction at each site is about 2 × 10 −18 .

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“…Since 1992 various fabricants provided successively the model 5071A, operated in almost all the time and frequency metrology laboratories for its good stability, better than 1 × 10 −14 at intervals [18] of five days or more, and accuracy of about five parts in 10 13 . The first commercial cesium clocks were constructed in Switzerland (Ebauches), and the United States (Hewlett-Packard).…”

Section: The Atomic Standardsmentioning

confidence: 99%

The Hyperfine Transition for the Definition of the Second

Arias

Petit

2019

Annalen der Physik

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The unit of time of the International System of Units (SI), the "atomic second" was defined through a constant of physics in 1967. It is derived from the frequency of the hyperfine transition of the atom of cesium 133. From the astronomical definition of the second until today, the accuracy of the realization of the second has improved by eight orders of magnitude, with a rate that has increased since the development of the cesium frequency standards, to reach parts in 10 16 for the best clocks today. In 2018, when the new SI was adopted, the time metrology community proved that a new generation of frequency standards operating in optical wavelengths has uncertainties at the level of 10 -18 , and challenge the implementation of high accurate frequency and time comparison techniques to decide on a revision of the definition of the second. Herein, the progress in the definition and realization of the second from astronomy until today is reviewed, an inventory of the present resources is assembled and a brief view for the future given.

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Atomic time-keeping from 1955 to the present

Cited by 53 publications

References 24 publications

Optical atomic clocks

Optical atomic clocks

Geodetic methods to determine the relativistic redshift at the level of 10 $$^{-18}$$ - 18 in the context of international timescales: a review and practical results

The Hyperfine Transition for the Definition of the Second

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