Report from TCTF/TCL JWG on Optical Frequency Metrology - Masami Yasuda Time Standards Group, National Metrology Institute of Japan (NMIJ), APMP
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Report from TCTF/TCL JWG on Optical Frequency Metrology Masami Yasuda Time Standards Group, National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST) TCTF/TCL Meeting Online 13 Nov. 2020
APMP TCTF/TCL JWG on OFM from 2007 • Main subjects of the WG: • Optical frequency comb research activities • Optical clock research activities • Microwave and optical frequency dissemination • Optical frequency combs and CCL-K11 2
Predicting when the redefinition happens • After the following 5 milestones are attained 1. At least three different optical clocks have validated uncertainties two orders of magnitude better than the best Cs atomic clocks (few 10-18). 2. Three or more optical clocks with the same atomic species were compared in different institutes (e.g. Δν/ν < 5 x 10-18)(either by transportable clocks, fiber links, or frequency ration closure). 3. There are three independent measuremens of the optical frequency standards listed in item 1 limited essentially by the uncertainty fo the best Cs fountain clocks (e.g. < 3 x 10-16). 4. Optical clocks (SRS) contribute regularly to TAI. 5. Optical frequency ratios between a few (at least 5) other optical frequency standards have been performed; each ratio measured at least twice by independent labs and agreement (with e.g. < 5 x 10-18). The new definition of the second should take place as early as possible as late as necessary. 3
Predicting when the redefinition happens Road map 3 clocks 1. ∆ / ~10−18 2 orders of magnitude smaller uncertainty with Cs 3 comparisons Clock comparisons 2. ∆ / < 5 × 10−18 3 clocks Continuity of the second 3. ∆ / < 3 × 10−16 4. Regular contribution to TAI At least ten days operation 2 comp. b/w 5 clocks 5. Optical frequency ratios ∆ / / / < 5 × 10−18 Validation and decision for optical standard CCTF CGPM CCTF CGPM CGPM CGPM 2017 2018 2020~2021 2022 2025 2026 2030 CCTF Strategy Document, Annex 1 (Towards a new definition of the second in the SI, F. Riehle) 4
Secondary Representation of the Second (2017) Frequency / Hz Fractional uncertainty Transition Status 6 834 682 610.904 312 6 6 x 10-16 87Rb Revised 2017 Ground state hfs 310 7 x 10-16 2015 value 429 228 004 229 873.0 4 x 10-16 87Sr neutral atom, Revised 2017 5s2 1S0-5s5p 3P0 873.2 5 x 10-16 2015 value 444 779 044 095 486.5 1.5 x 10-15 88Sr+ion, Revised 2017 5s 2S1/2-4d 2D5/2 486.6 1.6 x 10-15 2015 value 518 295 836 590 863.6 5 x 10-16 171Yb neutral atom, Revised 2017 6s2 1S0-6s6p 3P0 864.0 2 x 10-15 2015 value 642 121 496 772 645.0 6 x 10-16 171Yb+ ion, Not revised 6s 2S -5d 2F 1/2 7/2 688 358 979 309 308.3 6 x 10-16 171Yb+ ion, Not revised 6s 2S -5d 2D 1/2 3/2 1 064 721 609 899 145.3 1.9 x 10-15 199Hg+ion, Not revised 5d106s 2S1/2-5d96s2 2D5/2 1 121 015 393 207 857.3 1.9 x 10-15 27Al+ ion, Not revised 3s2 1S0-3s3p 3P0 1 128 575 290 808 154.4 5 x 10-16 199Hg neutral atom, New 2017 5 6s2 1S0-6s6p 3P0
h 13-15 UTC Task Force on the Roadmap for the redefinition of second Subgroup A: Needs of user communities, NMIs, and Liaisons Subgroup C: T&F Dissemination and time scales Subgroup B : Atomic frequency standards and possible redefinition approaches • Draft presentation for CCTF (presented on Oct. 28 for the CCTF online session) Document by S. Bize (OP) Aug. 24, 2020
Subgroup B members Chairs: Sébastien Bize, Chris Oates, Ekkehard Peik Executive secretary: Gérard Petit Members: Tetsuya Ido, Pierre Dubé, Stefan Weyers, Davide Calonico, Helen Margolis, Masami Yasuda, Dai- Hyuk Yu, Sergey Sluysarev, Fang Fang External contributors: Jérôme Lodewyck: on definition using several transitions on an even basis David Newell: on impact on the work and the outputs of CODATA Jean-Philippe Uzan: on impact of astronomy and astrophysics sector Review: Bill Phillips Document by S. Bize (OP) 7 Aug. 24, 2020
Status and capabilities of optical frequency standards • Status of optical frequency standards • Progress of optical frequency standards up to now • Accuracy, stability • 1 or 2 example, few other main references. • Comparisons of identical standards and ratios • 1 or 2 example, main other main references. • Comparisons with Cs • 1 or 2 example, main other main references. • Noting that a more comprehensive table of peer-reviewed references will be annexed to the document • Work toward transportable, commercial and space clocks • Noting that these are not required for redefinition, desirable on the long term • 1 or 2 examples, few other references Document by S. Bize (OP) 8 Aug. 24, 2020
Secondary representation of the second • What they are • Mention CCL-CCTF WG FS, refer to Metrologia 55, 188 (2018) • How they are a mean to validate the consistency of between measurements and the status the field • List of SRS to date (2017), link to BIPM website • Number of inputs so far, number of new inputs (2020) • Current use of SRS in TAI • Highlight compatibility of optical frequency standards with existing architectures (thanks to combs) • Contributions to TAI so far (graphic) • Highlighting scarcity of contributions, importance to consider sustainability of TAI • Toward optical timescales • Noting the big potential (1E-15 at 1 s corresponds to 1 fs) • Few references. Challenges. Document by S. Bize (OP) 9 Aug. 24, 2020
Options for a redefinition of the second • Single atom • Pointing the role of SRS • To be redefined after major progress • Several transition on an even basis • Realization using frequency ratio matrix from CIPM • Need to define/adopt rules for updating the ensemble and weights • Fundamental • Fixing another fundamental constant. Briefly developing two possibilities: G and m_e • Give practical uncertainties of realization in these cases • one of the above options will be a mise en pratique Document by S. Bize (OP) 10 Aug. 24, 2020
Considering some impacts of a redefinition • What will happen at and after redefinition • Cs will become a SRS. Initially recommended value will be 9192631770 Hz with an uncertainty of 1 to 4E-16. May evolve (improve) if Cs standards continue to progress as well as their measurement in SI unit. • Commercial Cs standards will continue realizing the SI second, virtually with an unchanged uncertainty. • Cs fountains will continue realizing the SI second with a slightly degraded uncertainty, because the uncertainty of the Cs recommended value will have to be added. • Cs (and other SRS) can and will continue to calibrate TAI (probably for quite some time) • More and more optical frequency standards (are accepted to) contribute to TAI, gradually leading to improvement of the timescale • TAI continues to be disseminate the SI second to few 1E-16 or better • Impact on SI system, on other (base) units • Technically: none because of the gap in uncertainties • Positive: SI system following state-of-the-art, avoid de facto standards in some area (especially atomic physics) • Negative: potential lack of support for existing infrastructure (especially Cs fountains) too soon. Document by S. Bize (OP) 11 Aug. 24, 2020
Considering some impacts of a redefinition • Impact on CODATA • External contributor: D. Newell • With special mention of / attention to the atomic physics sector • Impact astrophysics and fundamental physics • External contributor: J.-P. Uzan • Impact on time and space reference systems (inc. TAI) • Gravitational potential / potential fluctuations are not a severe limit until ~3E-18 • time and space reference systems, realization of TT, can largely benefit better standards, already in their current paradigm/definition Document by S. Bize (OP) 12 Aug. 24, 2020
Comparing options • Some high-level requirements • New definition must last long • Continuity between old and new definition must but ensured • Effectiveness and sustainability of dissemination • In particular in the elaboration of TAI • Optical frequency standards must have validated uncertainties • At a level much better than Cs standards (e.g. 2 orders of magnitudes) • Comparative analysis Accuracy Connection Potential for (current and with Durability Readiness and Understanda industrial mid-term fundamental of Continuity sustainability ble by broad and space Option potential) physical laws definition with Cs Dissemination for TAI audience standards transition X transition Y transition Z Multiple transitions Fixing another constant Document by S. Bize (OP) 13 Aug. 24, 2020
Recommendations • Increase contribution to TAI • Demonstrate sustainability • More ratios and direct comparisons to
Contribution to TAI
CCL-K11 Key Comparison 2020 in APMP • NMIJ conduct a CCL-K11 key comparison as the node lab in APMP in 2020. Date: April 20 (Mon) ~ 24 (Fri), 2020. Place: NMIJ (Tsukuba, Japan) • Frequency measurement using a frequency comb. • Travel expenses: At each NMI’s expense • Participants(9): New Zealand, China, Singapore, Malaysia, Thailand, Korea, Taiwan, Hong Kong, Vietnam • Contact us immediately if you hope to participate in the K11 in a country other than the above. We welcome you all to Japan after ten years!
Integration for Innovation Thank you for your attention!
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