International atomic time: Status and future challenges

Petit, Gérard; Arias, F.; Panfilo, G.

doi:10.1016/j.crhy.2015.03.002

Cited by 29 publications

(50 citation statements)

References 36 publications

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“…About ten of these devices are operating continuously and report their accuracy to BIPM for the realization of the International Atomic Time and UTC, the Universal Coordinate Time [34]. The fountain clock relative frequency stability is in the range 2-15·10 −14 τ −1/2 , where τ is the averaging time in seconds, reaching 1·10 −16 after a few days of integration [25].…”

Section: The Cold Atom Cesium Clock Pharaomentioning

confidence: 99%

The ACES/PHARAO space mission

Laurent

Massonnet

Cacciapuoti

et al. 2015

Comptes Rendus. Physique

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Section: The Cold Atom Cesium Clock Pharaomentioning

confidence: 99%

The ACES/PHARAO space mission

Laurent

Massonnet

Cacciapuoti

et al. 2015

Comptes Rendus. Physique

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“…We then use this ratio matrix to update the normalisation constant of the unit N according to equation (17). Equipped with the knowledge of the exact frequency ratios that our simulation provides us with, we then calculate the frequency of the unit and the accuracy of its realisation with clocks based on each transition using equations (11) and (12) respectively. Figure 4.…”

Section: Evolutionmentioning

confidence: 99%

“…With the new unit proposed in this paper, all contributing clocks would be steering as SRS are steering now. Namely, one would produce the frequency unit by scaling the frequency of a clock based on the atomic transition i by the factor 1/N i , as expressed by equation (12), and use it to calibrate the frequency of the local oscillator used as a pivot to connect to TAI. The relative uncertainty on N i would be used to fill the u Srep entry of the circular T. With the definition of the time unit proposed here, TAI would thus remain a truly atomic time, in the sense that all atomic transitions would contribute to TAI on an equal footing, with an added uncertainty δN i /N i expressing how well the transition is connected to the unit.…”

Section: From a Single Primary Frequency Standard To Multiple Clock Tmentioning

confidence: 99%

On a definition of the SI second with a set of optical clock transitions

Lodewyck

2019

Metrologia

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The current SI second based on the atomic hyperfine transition in the ground state of 133 Cs is expected to be replaced by a new definition based on optical frequency standards, whose estimated uncertainty has now been established two orders of magnitude lower than the accuracy of the best Cs primary standards. However, such a redefinition of the second is hindered by the fact that many atomic species are potential contenders to become the new primary frequency standard. In this paper, we propose to resolve this issue by defining a composite frequency unit based on the weighted geometric mean of the individual frequencies of different atomic transitions. This unit has the property to be realisable with any single clock whose transition composes the unit, provided that at least a few frequency ratios are available, with an accuracy that marginally differs from the nominal clock uncertainty. We show that the unit can be updated as the performances of the contributing transitions evolve, without incurring a drift on the unit itself.

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“…We remind that a meaningful definition and realization of a time scale valid globally in the vicinity of the Earth requires the framework of general relativity, in particular to properly account for Einstein's gravitational redshift which is about 10 −16 per meter of elevation at the surface of the Earth. A description of elaboration of TAI by the BIPM can be found for example in [46] and references therein. By means of satellite-based comparisons, data from about 450 continuously operated commercial clocks are used to compute the free atomic time scale (EAL).…”

Section: Elaboration Of Tai: Accuracy Of Atomic Fountains Delivered Tmentioning

confidence: 99%

The unit of time: Present and future directions

Bize

2019

Comptes Rendus. Physique

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Some 50 years ago, physicists, and after them the entire world, started to found their time reference on atomic properties instead of motions of the Earth that have been in use since the origin. Far from being an arrival point, this decision marked the beginning of an adventure characterized by a 6 orders of magnitude improvement in the uncertainty of realization of atomic frequency and time references. Ever progressing atomic frequency standards and time references derived from them are key resources for science and for society. We will describe how the unit of time is realized with a fractional accuracy approaching 10 −16 and how it is delivered to users via the elaboration of the international atomic time. We will describe the tremendous progress of optical frequency metrology over the last 20 years which led to a novel generation of optical frequency standards with fractional uncertainties of 10 −18 . We will describe work toward a possible redefinition of the SI second based on such standards. We will describe existing and emerging applications of atomic frequency standards in science.

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International atomic time: Status and future challenges

Cited by 29 publications

References 36 publications

The ACES/PHARAO space mission

The ACES/PHARAO space mission

On a definition of the SI second with a set of optical clock transitions

The unit of time: Present and future directions

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