REVIEW 3 major objections 4 minor 63 references
Coordinated international comparisons between optical clocks connected via fiber and satellite links
T0 review · 3 major / 4 minor · reviewed 2026-08-15 · deepseek-v4-flash
Pith's one-line read This paper reports the largest coordinated comparison of optical clocks to date, simultaneously comparing ten clocks in six countries over fiber and satellite links and presenting 38 frequency ratios, including four measured directly for…
desk verdict Largest multi-lab optical clock comparison to date, with a genuinely useful dataset and correlation analysis, but the satellite-link uncertainty budget is partly self-calibrated and needs scrutiny before the numbers feed the least-squares adjustment. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The central object is the optical frequency ratio between two clock transitions, with a total fractional uncertainty made of clock systematic uncertainties ($u_B$), relativistic redshift uncertainty ($u_{RRS}$), link statistics, and maser extrapolation. The comparison machinery is a star-shaped phase-stabilized fiber network, whose links contribute under $10^{-18}$ after 1000 s, plus satellite links using Integer Precise Point Positioning (IPPP), with hydrogen masers acting as flywheels so that clock data gaps can be bridged. The load-bearing model is the IPPP frequency transfer uncertainty $FTU = 1\times10^{-15}/(T/\mathrm{d})$, and the new analytical tool is the covariance calculation: the Fourier-transform method for extrapolation uncertainty is generalized to compute the covariance between two ratios that share a common maser, yielding correlation coefficients up to 0.94 for fiber ratios and 0.80 for GNSS ratios.
What would settle it
A direct comparison of the same two clocks over both a satellite link and a fiber link for at least 30 days would settle whether the transfer-uncertainty model holds: if the satellite-versus-fiber disagreement exceeds the combined uncertainties consistently, the model is optimistic. For the specific $4\times10^{-16}$ offset seen with the Italian Yb clock, feeding the same clock signal to two independent receivers through separate distribution chains during a GNSS-versus-fiber comparison would confirm whether the offset originates in the signal distribution.
Extended reading notes
Core claim
On its own terms, the paper establishes that a coordinated multi-clock, multi-link campaign can produce a dense, redundant set of optical frequency ratios whose cross-checks verify uncertainty budgets and expose inconsistencies. The 38 ratios include several GNSS links with total uncertainties below $1.8\times10^{-16}$, improving on the best previous satellite comparison, and the first direct measurements of Yb+(E3)/Yb, In+/Yb, Sr+/Sr, and Sr+/Yb. The redundancy revealed that all satellite-based ratios involving the Italian Yb clock are offset by about $4\times10^{-16}$ from fiber-based results, likely due to an unidentified problem in its signal distribution; the French Sr clock shows excess scatter and offsets near $1\times10^{-16}$; and the German Sr clock may have been a few $10^{-17}$ low. Because several discrepancies are ambiguous—a clock may be wrong, or the reference value derived from previous data may be wrong—the paper presents the results with a full $38\times38$ correlation matrix so future adjustments can use them correctly.
Load-bearing premise
The satellite-based results rest on the assumption that the noise added by the satellite link and by the auxiliary hydrogen clocks used to fill gaps in the optical-clock data is no larger than the model used to compute the uncertainties; if the real noise is larger, the reported uncertainties on the thirty satellite-based ratios are too small and the comparisons built on them shift.
Editorial extensions
If this is right
- The first direct measurements of the Yb+(E3)/Yb, In+/Yb, Sr+/Sr, and Sr+/Yb ratios will feed into the next least-squares adjustment of recommended optical frequencies, with the fiber-based Yb+(E3)/Yb value (about $5\times10^{-17}$ uncertainty) expected to pull the optimized value significantly.
- Several satellite-based ratios with total uncertainties below $1.8\times10^{-16}$ show that IPPP with maser flywheels can audit optical clocks across continents at a level previously reached only by fiber or local comparisons.
- The full correlation matrix, with 242 non-zero coefficients, allows all 38 ratios to be combined in future multivariate adjustments without double-counting shared clocks, links, and masers.
- The campaign's identified inconsistencies—the Italian Yb satellite offset, the French Sr scatter, and the possible German Sr offset—demonstrate that redundant multi-clock, multi-link measurements can uncover problems that pairwise comparisons would leave hidden.
Reading between the lines
- If the FTU model continues to hold, the same satellite-plus-maser procedure could make routine intercontinental comparisons of optical clocks at the $10^{-16}$ level, and the covariance formalism could be extended to networks that mix fiber and future free-space optical links.
- A testable extension would be to operate the Italian Yb clock with two independent radio-frequency distribution paths during a simultaneous fiber-and-GNSS comparison; if the $4\times10^{-16}$ offset reproduces only on the satellite side, the problem is in the distribution chain rather than the clock itself.
- The correlation machinery for common-maser extrapolation could be reused for optical time scales, where a single flywheel oscillator bridges gaps in real time; the same covariance formulas would quantify how much of the time-scale noise is shared between successive clock comparisons.
Signed reviews
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. This manuscript reports a 45-day coordinated campaign in 2022 in which ten optical clocks at six institutes were compared simultaneously, using a mix of local, international optical-fiber, and GNSS IPPP links. The paper presents 38 optical frequency ratios, of which four are claimed as first direct measurements (Yb+(E3)/Yb, In+/Yb, Sr+/Sr, Sr+/Yb), and it provides a 38x38 correlation analysis. The authors identify several anomalies, most notably an unexplained ~4e-16 offset in all GNSS comparisons involving the INRIM Yb clock, a possible uncontrolled shift in the SYRTE Sr clock, and a possible few-1e-17 offset in the PTB Sr clock. The abstract and conclusions use these results to argue that coordinated multi-lab optical clock networks are feasible and that the data will support the redefinition of the second.
Significance. If the uncertainty estimates are accepted, this is a landmark dataset: it is the densest simultaneous cross-checked comparison of optical clocks to date, it demonstrates the operation of a multi-link network with two independent transfer techniques, and it adds genuinely new direct frequency ratios that will feed into the next CIPM adjustment. The paper's strengths are its internal cross-checks (fiber versus GNSS, same-transition ratios, double GNSS receivers), the explicit correlation analysis, and the unusually candid reporting of anomalies. The main risk is that the uncertainty budget for the satellite-based ratios is not fully independent of the measured data, and the paper itself warns that some quoted uncertainties may be too small. Because the reliability of the quoted error bars is load-bearing for the '38 ratios', the 'lowest satellite comparison uncertainty' claim, and the offsets interpreted in Section 5, the manuscript needs revision before the results can be used with confidence.
major comments (3)
- [Section 4 and Supplementary Material Sec. 3.4] The uncertainties of the 26 GNSS-based ratios rest on noise models that are calibrated, at least in part, with the campaign's own data. The hydrogen-maser noise models in Table S2 are stated to be 'estimated using optical clock vs HM data from the campaign and/or prior information' (Section 4), and the IPPP phase-noise model in Eq. (5) has its amplitude k^-1 adjusted 'to make the FTU agree with the conservative estimate' and its low cutoff f_l = 1/(30 d) chosen to reproduce the autocorrelation from the same IPPP-fiber comparison (Supplementary Sec. 3.4). This makes the uncertainty budget not fully independent of the measured ratios, so an unmodeled common excess noise during this particular campaign would be invisible and would propagate into all GNSS ratios. Please add a sensitivity analysis (e.g., doubling the maser noise coefficients and the IPPP amplitude, or using independent long-term maser characterizations) and report how the claimed uncertainties and the 'lowest satellite comparison uncertainty' statement change.
- [Section 5.1 and Table 2] The paper declares 'we consider the results of all the frequency ratios via GNSS to INRIM to be unreliable' but still lists these seven ratios (rows 14, 16, 24, 25, 27, 28 and 29) in Table 2 with quantitative uncertainties and includes them in Fig. 2 and in the '38 frequency ratios' claims of the abstract and Section 7. This ambiguity is load-bearing because a reader combining these ratios with future data or with the CIPM adjustment could use uncertainties that the authors themselves state are wrong by about 4e-16. Please either mark these rows explicitly as unreliable (and exclude them from the headline count of usable ratios), or add a systematic uncertainty term that accounts for the observed offset.
- [Section 5.2 and the Birge-ratio treatment in Section 3] The paper reports a fractional frequency difference of 1.46(21)e-16 between PTB Sr and SYRTE Sr on the fiber link and states that SYRTE Sr had an uncontrolled shift at the 1e-16 level and PTB Sr possibly a few 1e-17, with Birge ratios of 3.3-5.3 for ratios involving SYRTE Sr (Supplementary Fig. S1). Nevertheless, Table 2 does not add any correlated systematic uncertainty for these clocks, so the 'agreement within 1-2 sigma' statements for the Sr/Sr and Yb+(E3)/Sr comparisons are likely understated. The Birge-ratio inflation acts on each ratio independently and cannot capture a common-mode clock shift that affects all ratios sharing a clock. Please either assign an additional, explicitly correlated uncertainty to the suspect clocks or clearly reclassify the affected ratios as consistency checks rather than precision results.
minor comments (4)
- [Table 2 caption] The caveat that 'some of the frequency ratios have significantly larger uncertainties than the estimates shown here' should be made actionable: list the affected row numbers and state explicitly whether users should treat those ratios as upper limits, as invalid, or as needing an extra uncertainty.
- [Fig. 2] The ratio ID numbers and the 'inv' markers are difficult to read at publication size; please enlarge the labels or split the figure so that the GNSS and fiber/local panels are legible.
- [Data Availability Statement] For a paper whose central contribution is a dataset, 'Data underlying the results ... may be obtained from the authors upon reasonable request' limits reproducibility; please consider releasing at least the daily-binned ratios and the correlation/covariance matrix.
- [Section 7, first paragraph] The sentence 'We have demonstrated agreement between GNSS and optical fiber links over a continental scale' should be qualified, since Section 5.1 removes the INRIM GNSS data from that conclusion.
Circularity Check
No formal circularity: the 38 ratios are direct measurements cross-validated against independent link techniques and external reference values.
full rationale
The paper's central deliverable is a set of measured optical frequency ratios obtained from simultaneous clock operation, fiber links, and GNSS/IPPP comparison. The values are not derived from a fitted model or from a self-citation. Cross-checks include fiber-vs-GNSS agreement, same-transition ratios expected to equal 1, and comparisons against the CIPM 2021 least-squares reference values, which are external to this campaign. The Birge-ratio inflation, maser-noise models estimated partly from campaign data, and the IPPP autocorrelation model are uncertainty-estimation procedures; they affect the quoted error bars but do not enter the frequency-ratio values, so they are self-calibration limitations rather than circular derivations. The Table 2 caveat that some GNSS ratios may have significantly larger uncertainties is an honesty flag about the uncertainty model, not a circular reduction. The single use of the authors' prior work to interpret the PTB Sr offset ([29]) relies on further measurements and does not support the measured ratios, so it is not load-bearing. Consequently, no step satisfies the 'reduces by construction' test; score 0.
Assumptions & free parameters
free parameters (6)
- IPPP frequency transfer uncertainty coefficient =
1e-15/(T/d), and 1.3e-15/(T/d) for the NM0D receiver
- IPPP phase PSD model amplitude =
k^-1 = 4.6e-22 s^2/Hz
- IPPP phase PSD low cut-off frequency =
1/(30 d)
- Maser noise model coefficients =
Six sets of h2, h0, h-1, h-2 and optional Lorentzian peak parameters, see Table S2
- Birge ratio inflation factors =
1 to 2.1 for most fiber and local ratios; 3.3 to 5.3 for ratios involving SYRTE Sr
- Hydrogen maser drift rates =
Per institute, from linear fits to clock-vs-maser data
assumptions (6)
- domain assumption The empirical IPPP frequency transfer uncertainty FTU = 1e-15/(T/d), and 1.3e-15/(T/d) for the NM0D receiver, bounds GNSS link noise over analysis intervals up to about 100 days.
- domain assumption Hydrogen maser frequency noise is stationary and can be described as power-law noise (white phase, white frequency, flicker, random walk) plus optional Lorentzian bumps, with parameters from Table S2.
- domain assumption Excess daily scatter in fiber ratios is fully captured by inflating statistical uncertainties by the Birge ratio computed from those same daily bins.
- domain assumption The 2021 CIPM least-squares reference frequency ratios provide valid expected values for different-transition ratios, except where the paper argues the reference is suspect, for Sr+ and In+.
- domain assumption The relativistic redshift correction relative to the conventional potential W0 = 62,636,856.00 m^2/s^2 is accurate to the u_RRS uncertainties in Table 1.
- ad hoc to paper The unidentified 4e-16 offset observed in GNSS ratios involving INRIM affected all and only those GNSS ratios during the campaign, so excluding all such ratios is valid.
Cite this review
Pith. "Pith review of Coordinated international comparisons between optical clocks connected via fiber and satellite links." pith.science (2026). https://pith.science/paper/RQEFMTNY
@misc{pith2026250506763,
author = {Pith},
title = {Pith review of: Coordinated international comparisons between optical clocks connected via fiber and satellite links},
year = {2026},
howpublished = {\url{https://pith.science/paper/RQEFMTNY}},
note = {Machine review of arXiv:2505.06763}
}
read the original abstract
Optical clocks provide ultra-precise frequency references that are vital for international metrology as well as for tests of fundamental physics. To investigate the level of agreement between different clocks, we simultaneously measured the frequency ratios between ten optical clocks in six different countries, using fiber and satellite links. This is the largest coordinated comparison to date, from which we present a subset of 38 optical frequency ratios and an evaluation of the correlations between them. Four ratios were measured directly for the first time, while others had significantly lower uncertainties than previously achieved, supporting the advance towards a redefinition of the second and the use of optical standards for international time scales.
Figures
Reference graph
Works this paper leans on
- [1]
- [2]
- [3]
-
[4]
N. Sherrill, A. O. Parsons, C. F. A. Baynham, et al., Analysis of atomic-clock data to constrain variations of fundamental constants, New Journal of Physics 25, 093012 (2023)
work page 2023
-
[5]
B. M. Roberts, P. Delva, A. Al-Masoudi, et al., Search for transient variations of the fine structure constant and dark matter using fiber-linked optical atomic clocks, New Journal of Physics 22, 093010 (2020)
work page 2020
- [6]
-
[7]
T. Kobayashi, A. Takamizawa, D. Akamatsu, et al., Search for ultralight dark matter from long-term frequency comparisons of optical and microwave atomic clocks, Phys. Rev. Lett. 129, 241301 (2022)
work page 2022
-
[8]
M. Filzinger, S. D\"orscher, R. Lange, et al., Improved limits on the coupling of ultralight bosonic dark matter to photons from optical atomic clock comparisons, Phys. Rev. Lett. 130, 253001 (2023)
work page 2023
Show all 63 references
-
[9]
C. W. Chou, D. B. Hume, T. Rosenband, and D. J. Wineland, Optical clocks and relativity, Science 329, 1630--1633 (2010)
2010
-
[10]
Grotti, S
J. Grotti, S. Koller, S. Vogt, et al., Geodesy and metrology with a transportable optical clock, Nature Physics 14, 437--441 (2018)
2018
-
[11]
Takamoto, I
M. Takamoto, I. Ushijima, N. Ohmae, et al., Test of general relativity by a pair of transportable optical lattice clocks, Nature Photonics 14, 411--415 (2020)
2020
-
[12]
Dimarcq, M
N. Dimarcq, M. Gertsvolf, G. Mileti, et al., Roadmap towards the redefinition of the second, Metrologia 61, 012001 (2024)
2024
-
[13]
Grebing, A
C. Grebing, A. Al-Masoudi, S. D\" o rscher, et al., Realization of a timescale with an accurate optical lattice clock, Optica 3, 563--569 (2016)
2016
-
[14]
Hachisu, F
H. Hachisu, F. Nakagawa, Y. Hanado, and T. Ido, M onths-long real-time generation of a time scale based on an optical clock, Sci. Rep. 8, 4243 (2018)
2018
-
[15]
J. Yao, J. A. Sherman, T. Fortier, et al., Optical-clock-based time scale, Phys. Rev. Appl. 12, 044069 (2019)
2019
-
[16]
Formichella, G
V. Formichella, G. Signorile, T. Thai, et al., Year-long optical time scale with sub-nanosecond capabilities, Optica 11 (2024)
2024
-
[17]
Takamoto, I
M. Takamoto, I. Ushijima, M. Das, et al., Frequency ratios of Sr, Yb, and Hg based optical lattice clocks and their applications, Comptes Rendus. Physique 16, 489--498 (2015)
2015
-
[18]
Riedel, A
F. Riedel, A. Al-Masoudi, E. Benkler, et al., Direct comparisons of E uropean primary and secondary frequency standards via satellite techniques, Metrologia 57, 045005 (2020)
2020
-
[19]
International Clock and Oscillator Networking (ICON) Collaboration , International comparison of optical frequencies with transportable optical lattice clocks, https://arxiv.org/abs/2410.22973 (2024)
2024 arXiv
-
[20]
H. S. Margolis, G. Panfilo, G. Petit, et al., The CIPM list ‘ R ecommended values of standard frequencies’: 2021 update, Metrologia 61, 035005 (2024)
2024
-
[21]
H. S. Margolis, R. M. Godun, N. Huntemann, et al., Robust optical clocks for international timescales ( ROCIT ), Journal of Physics: Conference Series 2889, 012022 (2024)
2024
-
[22]
Lisdat, G
C. Lisdat, G. Grosche, N. Quintin, et al., A clock network for geodesy and fundamental science, Nature Communications 7, 12443 (2016)
2016
-
[23]
S. Koke, A. Kuhl, T. Waterholter, et al., Combining fiber brillouin amplification with a repeater laser station for fiber-based optical frequency dissemination over 1400 km, New Journal of Physics 21, 123017 (2019)
2019
-
[24]
Cantin, M
E. Cantin, M. Tønnes, R. Le Targat, et al., An accurate and robust metrological network for coherent optical frequency dissemination, New Journal of Physics 23, 053027 (2021)
2021
-
[25]
Clivati, M
C. Clivati, M. Pizzocaro, E. K. Bertacco, et al., Coherent optical-fiber link across I taly and F rance, Phys. Rev. Appl. 18, 054009 (2022)
2022
-
[26]
Petit, A
G. Petit, A. Kanj, S. Loyer, et al., 1 10^ -16 frequency transfer by GPS PPP with integer ambiguity resolution, Metrologia 52, 301 (2015)
2015
-
[27]
I. Goti, S. Condio, C. Clivati, et al., Absolute frequency measurement of a Yb optical clock at the limit of the Cs fountain, Metrologia 60, 035002 (2023)
2023
-
[28]
Lodewyck, S
J. Lodewyck, S. Bilicki, E. Bookjans, et al., Optical to microwave clock frequency ratios with a nearly continuous strontium optical lattice clock, Metrologia 53, 1123--1130 (2016)
2016
-
[29]
H. N. Hausser, J. Keller, T. Nordmann, et al., ^ 115 In ^+ - ^ 172 Yb ^+ C oulomb crystal clock with 2.5 10^ -18 systematic uncertainty, Physical Review Letters 134, 023201 (2025)
2025
-
[30]
Kobayashi, D
T. Kobayashi, D. Akamatsu, K. Hosaka, et al., Demonstration of the nearly continuous operation of an 171yb optical lattice clock for half a year, Metrologia 57, 065021 (2020)
2020
-
[31]
Hobson, W
R. Hobson, W. Bowden, A. Vianello, et al., A strontium optical lattice clock with 1 10^ -17 uncertainty and measurement of its absolute frequency, Metrologia 57, 065026 (2020)
2020
-
[32]
Tofful, C
A. Tofful, C. F. A. Baynham, E. A. Curtis, et al., ^ 171 Yb ^+ optical clock with 2.2 10^ -18 systematic uncertainty and absolute frequency measurements, Metrologia 61, 045001 (2024)
2024
-
[33]
Schwarz, A cryogenic strontium lattice clock, Ph.D
R. Schwarz, A cryogenic strontium lattice clock, Ph.D. thesis, Gottfried Wilhelm Leibniz Universität Hannover (2022)
2022
-
[34]
Lindvall, K
T. Lindvall, K. J. Hanhij\"arvi, T. Fordell, and A. E. Wallin, High-accuracy determination of P aul-trap stability parameters for electric-quadrupole-shift prediction, J. Appl. Phys. 132, 124401 (2022)
2022
-
[35]
Denker, L
H. Denker, L. Timmen, C. Voigt, et al., Geodetic methods to determine the relativistic redshift at the level of 10^ -18 in the context of international timescales: a review and practical results, J. Geod. 92, 487--516 (2018)
2018
-
[36]
Schioppo, J
M. Schioppo, J. Kronjäger, A. Silva, et al., Comparing ultrastable lasers at 7 10^ -17 fractional frequency instability through a 2220 km optical fibre network, Nature Communications 13, 212 (2022)
2022
-
[37]
https://refimeve.fr/
-
[38]
Clivati, R
C. Clivati, R. Aiello, G. Bianco, et al., Common-clock very long baseline interferometry using a coherent optical fiber link, Optica 7, 1031--1037 (2020)
2020
-
[39]
Guillou-Camargo, V
F. Guillou-Camargo, V. Ménoret, E. Cantin, et al., First industrial-grade coherent fiber link for optical frequency standard dissemination, Appl. Opt. 57, 7203--7210 (2018)
2018
-
[40]
Lodewyck, R
J. Lodewyck, R. Le Targat, P.-E. Pottie, et al., Universal formalism for data sharing and processing in clock comparison networks, Phys. Rev. Research 2, 043269 (2020)
2020
-
[41]
Petit and P
G. Petit and P. Wolf, Relativistic theory for time comparisons: a review, Metrologia 42, S138 (2005)
2005
-
[42]
S. T. Dawkins, J. J. McFerran, and A. N. Luiten, C onsiderations on the measurement of the stability of oscillators with frequency counters, IEEE Trans. Ultrason., Ferroelectr., Freq. Control 54, 918--925 (2007)
2007
-
[43]
Leute, G
J. Leute, G. Petit, P. Exertier, et al., High accuracy continuous time transfer with GPS IPPP and T2L2 , in 2018 European Frequency and Time Forum ( EFTF ), ( IEEE , 2018), pp. 249--252
2018
-
[44]
Petit, Sub- 10^ -16 accuracy GNSS frequency transfer with IPPP , GPS Solut
G. Petit, Sub- 10^ -16 accuracy GNSS frequency transfer with IPPP , GPS Solut. 25, 22 (2021)
2021
-
[45]
Petit, F
G. Petit, F. Meynadier, A. Harmegnies, and C. Parra, Continuous IPPP links for UTC , Metrologia 59, 045007 (2022)
2022
-
[46]
H. S. Margolis, G. Panfilo, G. Petit, et al., Data associated with the 2021 adjustment of standard frequencies, https://www.bipm.org/en/doi/10.59161/stdfreq202301
2021 doi
-
[47]
Tiesinga, P
E. Tiesinga, P. J. Mohr, D. B. Newell, and B. N. Taylor, CODATA recommended values of the fundamental physical constants: 2018, J. Phys. Chem. Ref. Data 50, 033105 (2021)
2021
-
[48]
H. S. Margolis and P. Gill, Least-squares analysis of clock frequency comparison data to deduce optimized frequency and frequency ratio values, Metrologia 52, 628--634 (2015)
2015
-
[49]
Grotti, I
J. Grotti, I. Nosske, S. B. Koller, et al., Long-distance chronometric leveling with a portable optical clock, Phys. Rev. Applied 21, L061001 (2024)
2024
-
[50]
D \"o rscher, N
S. D \"o rscher, N. Huntemann, R. Schwarz, et al., Optical frequency ratio of a ^ 171 Yb^ + single-ion clock and a ^ 87 Sr lattice clock, Metrologia 58, 015005 (2021)
2021
-
[51]
Steinel, H
M. Steinel, H. Shao, M. Filzinger, et al., Evaluation of a ^ 88 Sr ^+ optical clock with a direct measurement of the blackbody radiation shift and determination of the clock frequency, Phys. Rev. Lett. 131, 083002 (2023)
2023
-
[52]
B. Jian, J. Bernard, M. Gertsvolf, and P. Dub \' e , Improved absolute frequency measurement of the strontium ion clock using a GPS link to the SI second, Metrologia 60, 015007 (2023)
2023
-
[53]
G. P. Barwood, G. Huang, H. A. Klein, et al., A greement between two ^ 88 Sr^+ optical clocks to 4 parts in 10 ^ 17 , Phys. Rev. A 89, 050501 (2014)
2014
-
[54]
BIPM, IEC, IFCC, et al., Evaluation of measurement data - G uide to the expression of uncertainty in measurement, Joint Committee for Guides in Metrology, JCGM 100 (2008)
2008
-
[55]
BIPM, IEC, IFCC, et al., Evaluation of measurement data – S upplement 2 to the `` G uide to the expression of uncertainty in measurement'' – E xtension to any number of output quantities, Joint Committee for Guides in Metrology, JCGM 102 (2011)
2011
-
[56]
H. S. Margolis and M. Pizzocaro, Guidelines on the evaluation and reporting of correlation coefficients between frequency ratio measurements, https://empir.npl.co.uk/rocit/wp-content/uploads/sites/52/2021/02/ROCIT_guidelines_on_correlations.pdf (2020)
2020
-
[57]
Optical link data format, https://github.com/INRIM/optical-link-data-format
-
[58]
Ohmae, F
N. Ohmae, F. Bregolin, N. Nemitz, and H. Katori, Direct measurement of the frequency ratio for Hg and Yb optical lattice clocks and closure of the Hg/Yb/Sr loop, Opt. Express 28, 15112--15121 (2020)
2020
-
[59]
Ushijima, M
I. Ushijima, M. Takamoto, M. Das, et al., Cryogenic optical lattice clocks, Nature Photonics 9, 185--189 (2015)
2015
-
[60]
Baillard, M
X. Baillard, M. Fouché, R. Le Targat, et al., An optical lattice clock with spin-polarized ^ 87 S r atoms, European Physical Journal D 48, 11--17 (2008)
2008
-
[61]
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[63]
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Reviewed August 15, 2026 · model on record in the stance chip above.
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