Absolute frequency measurement of the optical clock transition in with an uncertainty of using a frequency link to international atomic time

Abstract

The highly forbidden ${}^2{\mathrm{S}}_{1/2}\to {}^2{\mathrm{F}}_{7/2}$ electric octupole transition in ${}^{171}{\mathrm{Yb}}^{+}$ is a potential candidate for a redefinition of the SI second. We present a measurement of the absolute frequency of this optical transition, performed using a frequency link to International Atomic Time to provide traceability to the SI second. The ${}^{171}{\mathrm{Yb}}^{+}$ optical frequency standard was operated for 76% of a 25-day period, with the absolute frequency measured to be 642 121 496 772 645.14(26) Hz. The fractional uncertainty of $4.0\times {10}^{-16}$ is comparable to that of the best previously reported measurement, which was made by a direct comparison to local caesium primary frequency standards.

Keywords:

• Frequency metrology
• optical frequency standards
• international atomic time

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Publisher’s Note

Acknowledgements

We thank Peter Whibberley for helpful discussions and E. Anne Curtis for critical review of the manuscript prior to submission. We also note that our absolute frequency measurement derives its accuracy from the primary standards operated at other national measurement institutes around the world.

Notes

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was financially supported by the UK Department for Business, Energy and Industrial Strategy as part of the National Measurement System Programme; the European Metrology Research Programme (EMRP) project SIB55-ITOC; and the European Metrology Programme for Innovation and Research (EMPIR) project 15SIB03-OC18. This project has received funding from the EMPIR programme co-financed by the Participating States and from the European Union’s Horizon 2020 research and innovation programme. The EMRP is jointly funded by the EMRP participating countries within EURAMET and the European Union.