Comptes Rendus
Towards a redefinition of the second based on optical atomic clocks
Comptes Rendus. Physique, Volume 16 (2015) no. 5, pp. 506-515.

The rapid increase in accuracy and stability of optical atomic clocks compared to the caesium atomic clock as the primary standard of time and frequency asks for a future redefinition of the second in the International System of Units (SI). The status of the optical clocks based on either single ions in radio-frequency traps or on neutral atoms stored in an optical lattice is described, with special emphasis on the current work at the Physikalisch-Technische Bundesanstalt (PTB, Braunschweig, Germany). Besides the development and operation of different optical clocks with estimated fractional uncertainties in the 1018 range, the supporting work on ultra-stable lasers as core elements and the means to compare remote optical clocks with transportable standards, optical fibres, or frequency ratios is reported. Finally, the conditions, methods and next steps are discussed, which are the prerequisites for a future redefinition of the second.

L'amélioration rapide en termes de précision et de stabilité des horloges atomiques optiques par rapport à l'horloge atomique au césium, qui constitue la référence primaire pour le temps et la fréquence, appelle une future redéfinition de la seconde dans le système international d'unités (SI). L'état d'avancement des horloges optiques basées sur des ions uniques dans des pièges radiofréquence ou sur des atomes neutres confinés dans le réseau optique est décrit, en insistant particulièrement sur le travail en cours à la Physikalisch-Technische Bundesanstalt (PTB, Brunswick, Allemagne). À côté du développement et de la mise en œuvre de différentes horloges optiques avec des incertitudes fractionnelles estimées d'un ordre de grandeur de 1018, les travaux sous-jacents sur les lasers ultra-stables comme éléments centraux ainsi que les moyens de comparer les horloges optiques lointaines avec des étalons transportables, des fibres optiques ou des rapports de fréquence sont exposés. Finalement, les conditions, les méthodes et les prochaines étapes sont discutées, qui sont des prérequis à une redéfinition de la seconde.

Published online:
DOI: 10.1016/j.crhy.2015.03.012
Keywords: Optical atomic clocks, Frequency standards, Future redefinition of the second, Frequency and time dissemination
Mot clés : Horloges optiques atomiques, Étalons de fréquence, Redéfinition future de la seconde, Diffusion des fréquences et des signaux horaires

Fritz Riehle 1

1 Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig, Germany
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Fritz Riehle. Towards a redefinition of the second based on optical atomic clocks. Comptes Rendus. Physique, Volume 16 (2015) no. 5, pp. 506-515. doi : 10.1016/j.crhy.2015.03.012. https://comptes-rendus.academie-sciences.fr/physique/articles/10.1016/j.crhy.2015.03.012/

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