International timescales with optical clocks (ITOC)

Margolis, H. S.; Godun, R. M.; Gill, P.; Johnson, L. A. M.; Shemar, S. L.; Whibberley, Peter; Calonico, Davide; Levi, Filippo; Lorini, L.; Pizzocaro, Marco; Delva, Pacôme; Bize, S.; Achkar, Joseph; Denker, Heiner; Timmen, Ludger; Voigt, Christian; Falke, Stephan; Piester, D.; Lisdat, Christian; Sterr, U.; Vogt, S.; Weyers, S.; Geršl, Jan; Lindvall, Thomas; Merimaa, Mikko

doi:10.1109/eftf-ifc.2013.6702183

Cited by 16 publications

(29 citation statements)

References 21 publications

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“…The gravitational potential relative to the geoid at INRIM's laboratories was measured in 2013 in the con text of the European project 'International timescales with optical clocks' (ITOC) [44,45]. The measurement was performed both by a levelling approach and by a Global Navigation Satellite System/geoid (GNSS/geoid) approach [46] ( ) = − [48,49].…”

Section: Gravitational Redshiftmentioning

confidence: 99%

Absolute frequency measurement of the ${{}^{1}}{{\text{S}}_{0}}$ – ${{}^{3}}{{\text{P}}_{0}}$ transition of¹⁷¹Yb

et al. 2017

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We report the absolute frequency measurement of the unperturbed transition S 1 0 -P 3 0 at 578 nm in 171 Yb realized in an optical lattice frequency standard relative to a cryogenic caesium fountain. The measurement result is 518 295 836 590 863.59(31) Hz with a relative standard uncertainty of 5.9 10 16 × − . This value is in agreement with the ytterbium frequency recommended as a secondary representation of the second in the International System of Units.

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Section: Gravitational Redshiftmentioning

confidence: 99%

Absolute frequency measurement of the ${{}^{1}}{{\text{S}}_{0}}$ – ${{}^{3}}{{\text{P}}_{0}}$ transition of¹⁷¹Yb

et al. 2017

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“…The major differences between EGG2015 and the previous EGG2008 model (Denker 2013) are the inclusion of additional gravity measurements carried out recently around all major European optical clock sites within the ITOC project (Margolis et al 2013;Margolis 2014; see also http://projects. npl.co.uk/itoc/) and the use of a newer geopotential model based on the GOCE satellite mission instead of EGM2008.…”

Section: The European Gravimetric Quasigeoid Model Egg2015mentioning

confidence: 99%

“…This requires a coordinated programme of clock comparisons to gain confidence in the new generation of optical clocks within the international metrology community and beyond, to validate the corresponding uncertainty budgets, and to anchor their frequencies to the present definition of the second. Such a comparison programme has, for example, been carried out within the collaborative European project "International Timescales with Optical Clocks" (ITOC; Margolis et al 2013).…”

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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“…Pourtant, même les meilleures d'entre elles ne permettent pas de comparer des horloges avec une résolution meilleure que quelques 10 −16 après plusieurs semaines [31], et donc a fortiori de tirer parti de la stabilité offerte par les horloges à réseau optique. L'horloge Sr2 a été impliquée dans deux campagnes de comparaisons d'horloges par satellite, dans le cadre du projet européen ITOC [32]. L'une a duré 7 jours en octobre 2014 et l'autre 21 jours en juin 2015.…”

Section: Comparaisons Intracontinentalesunclassified

Horloges à réseau optique au strontium

Lodewyck¹,

Targat²,

Bilicki³

et al. 2016

R. franç. métrol.

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RésuméDans les horloges à réseau optique, des atomes froids confinés dans un piège dipolaire en forme de réseau sont interrogés par un laser ultrastable. Elles sont devenues les meilleurs étalons de fréquence car elles allient à la fois une résonance étroite dans le domaine optique, et donc grand facteur de qualité, et un grand nombre d'atomes interrogés simultanément. Dans cet article, nous présentons les derniers développements de ces horloges en termes de stabilité de fréquence et d'exactitude, en décrivant les résultats obtenus avec deux horloges à réseau optique au strontium développées au LNE-SYRTE. MOTS CLÉS : MÉTROLOGIE DU TEMPS ET DES FRÉQUENCES, HORLOGES À RÉSEAU OPTIQUE, ATOMES FROIDS, LASERS ULTRASTABLES. AbstractIn optical lattice clocks, an ensemble of cold neutral atoms confined in a lattice-shaped dipole trap are probed by an ultrastable laser. They have recently become the best frequency references, because they combine a narrow atomic resonance in the optical domain -hence a large quality factor -and a large number of simultaneously probed atoms. In this paper, we present the latest developments of these clocks, both in terms of frequency stability and accuracy, by focusing on two strontium optical lattice clocks under operation at LNE-SYRTE.

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International timescales with optical clocks (ITOC)

Cited by 16 publications

References 21 publications

Absolute frequency measurement of the ${{}^{1}}{{\text{S}}_{0}}$ – ${{}^{3}}{{\text{P}}_{0}}$ transition of¹⁷¹Yb

Absolute frequency measurement of the ${{}^{1}}{{\text{S}}_{0}}$ – ${{}^{3}}{{\text{P}}_{0}}$ transition of¹⁷¹Yb

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

Horloges à réseau optique au strontium

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International timescales with optical clocks (ITOC)

Cited by 16 publications

References 21 publications

Absolute frequency measurement of the ${{}^{1}}{{\text{S}}_{0}}$ – ${{}^{3}}{{\text{P}}_{0}}$ transition of171Yb

Absolute frequency measurement of the ${{}^{1}}{{\text{S}}_{0}}$ – ${{}^{3}}{{\text{P}}_{0}}$ transition of171Yb

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

Horloges à réseau optique au strontium

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Absolute frequency measurement of the ${{}^{1}}{{\text{S}}_{0}}$ – ${{}^{3}}{{\text{P}}_{0}}$ transition of¹⁷¹Yb

Absolute frequency measurement of the ${{}^{1}}{{\text{S}}_{0}}$ – ${{}^{3}}{{\text{P}}_{0}}$ transition of¹⁷¹Yb