Absolute frequency measurement of a Yb optical clock at the limit of the Cs fountain

We present the new absolute frequency measurement of ytterbium (171Yb) obtained at INRiM with the optical lattice clock IT-Yb1 against the cryogenic caesium (133Cs) fountain IT-CsF2, evaluated through a measurement campaign that lasted 14 months. Measurements are performed by either using a hydrogen maser as a transfer oscillator or by synthesizing a low-noise microwave for Cs interrogation using an optical frequency comb. The frequency of the 171Yb unperturbed clock transition ${^1}$S$_0\rightarrow {^3}$P0 results to be 518 295 836 590 863.44(14) Hz, with a total fractional uncertainty of $2.7 \times 10^{-16}$ that is limited by the uncertainty of IT-CsF2. Our measurement is in agreement with the Yb frequency recommended by the Consultative Committee for Time and Frequency. This result confirms the reliability of Yb as a secondary representation of the second and is relevant to the process of redefining the second in the International System of Units on an optical transition

Improving the resolution of comb-based frequency measurements using a track and hold amplifier

The advent of optical frequency standards with ultimate uncertainties in the low 1x10$^{-18}$ requires femtosecond frequency combs to support a similar level of resolution in the spectral transfer and the computation of optical frequency ratios. The related experimental challenges grow together with the number of optical frequencies to be measured simultaneously, as in many cases the comb's optical power does not allow reliable beatnote counting or tracking in all the spectral regions of interest. Here we describe the use of a track-and-hold amplifier to implement the gated detection, a previously proposed technique for improving the signal-to-noise ratio of the beatnote between a low-power tooth of the frequency comb and a continuous wave laser. We demonstrate a 12dB improvement in the signal-to-noise ratio of beatnotes involving a broadband-spanning optical comb as compared to traditional detection schemes. Our approach enables reliable and cycle-slip-free spectral purity transfer and reduces the system sensitivity to power drops in the comb spectrum. Being based on a single chip, it is robust, versatile and easily embedded in more complex experimental schemes. Keywords: frequency comb, spectral purity transfer, gated detection, track and hold amplifier

Dataset for the absolute frequency measurement of IT-Yb1 relative to IT-CsF2

Dataset of the comparison of the atomic clocks at INRIM between June 2021 and September 2022. Results discussed in Goti et al., Absolute frequency measurement of a Yb optical clock at the limit of the Cs fountain, Metrologia, 60, 035002 (2023). The involved atomic clocks are the Cs fountains IT-CsF2 and the Yb optical lattice clock IT-Yb1. Data is organized in folders. The data in the folder named 'INRIM_ITYb1-INRIM_ITCsF2-USO' is obtained making use of an optical-to-microwave chain. The data in the folder 'INRIM_ITYb1-INRIM_ITCsF2' is collected using an hydrogen maser as transfer oscillator. In the folders data is separated is one file per day. Data is reported as fractional frequency ratios in bins of 864 s. Timetags are reported in modified Julian date (MJD). A validity flag is given where 0 = invalid, valid otherwise. Each folder includes a yaml file with metadata required for generalized data processing as in [Lodewyck et al., 2020]. The Python package used for data processing can be found on github.This work is supported by: the European Metrology Program for Innovation and Research (EMPIR) Projects 18SIB05 ROCIT and 20FUN08 Nextlasers, which have received funding from the EMPIR programme co-financed by the Participating States and from the European Union's Horizon 2020 research and innovation programme

Atomic clock dataset for 'Coherent Optical-Fiber Link Across Italy and France'

Dataset of the comparison of the atomic clocks at LNE-SYRTE and INRIM via optical fibre link between October 2021 and February 2022. Results discussed in Clivati et al., Coherent Optical-Fiber Link Across Italy and France, Phys. Rev. Applied, American Physical Society, 18, 054009, 2022. The involved atomic clocks are the Cs fountains SYRTE-F02Cs, IT-CsF2, the Rb fountain SYRTE-F02Rb and the Yb optical lattice clock IT-Yb1. Data is organized in folders, one for each comparison. In the folders data is separated is one file per day. Data is reported as fractional frequency ratios in bins of 864 s. Timetags are reported in modified Julian date (MJD). A validity flag is given where 0 = invalid, valid otherwise. Each folder includes a yaml file with metadata required for generalized data processing as in [Lodewyck et al., 2020]. The Python package used for data processing can be found on github.This work was supported by: the European Metrology Program for Innovation and Research (EMPIR) Projects 18SIB05 ROCIT, 18SIB06 TIFOON, 20FUN08 NextLasers, which 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 European Union's Horizon 2020 research and innovation programme under Grant Agreement No. 951886 (CLONETS-DS); Program "Investissements d'Avenir" launched by the French Government and implemented by Agence Nationale de la Recherche with references ANR-10-LABX-48-01 (Labex First-TF), ANR-21-ESRE-0029 (ESR/Equipex T-REFIMEVE), ANR-11-EQPX-0039 (Equipex REFIMEVE+), ANR-10-IDEX-0001-002 (Idex PSL); Conseil Régional Bourgogne-Franche-Comté; Domaine d'Intérêt Majeur Science et Ingénierie en Région Île-de-France pour les Technologies Quantiques (DIM SIRTEQ)

A Coherent Optical Fibre Link Between France and Italy

International audienceWe report on the results obtained with the recently developed fiber link between LNE-SYRTE in France and INRIM in Italy. The link enables comparisons of different species of clocks, including Cs and Rb fountains, Sr and Yb optical lattice clocks, providing data to the roadmap for the redefinition of the second in the International System of Units

A Coherent Optical Fibre Link Between France and Italy

International audienceWe report on the results obtained with the recently developed fiber link between LNE-SYRTE in France and INRIM in Italy. The link enables comparisons of different species of clocks, including Cs and Rb fountains, Sr and Yb optical lattice clocks, providing data to the roadmap for the redefinition of the second in the International System of Units