Report from TCTF/TCL JWGon Optical Frequency Metrology

Masami Yasuda1 and Tetsuya Ido2

1Time Standards Group, National Metrology Institute of Japan (NMIJ),National Institute of Advanced Industrial Science and Technology (AIST)2Space-Time Standards Laboratory,National Institute of Information and Communcations Technology （NICT)

TCTF MeetingDelhi, India27 Nov. 2017

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

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Report on CCTF (CCL‐CCTF WGFS & WGPSFS)• Period: 6 June 2017• Place： BIPM (Sevres) • Participants: (CCL‐CCTF WGFS)

• Dr. John Bernard, NRC (Ottawa)• Dr. Davide Calonico, INRIM (Turin)• Dr. Zhanjun Fang, NIM (Beijing)• Prof. Feng‐Lei Hong, NMIJ/AIST (Tsukuba)• Mr. Sang‐Wook Hwang, KRISS (Daejeon)• Dr. Nikolai Koshelyaevsky, VNIIFTRI (Moscow)• Dr. Helen Margolis, NPL (Teddington)• Mr. Andrey Naumov, VNIIFTRI (Moscow)• Dr. Chris Oates, NIST (Gaithersburg)• Dr. Ekkehard Peik, PTB (Braunschweig)• Dr. Anders Wallin, MIKES (Espoo)• Dr. Masami Yasuda, NMIJ/AIST (Tsukuba)• Dr. Dai‐Hyuk Yu, KRISS (Daejeon)

• Participants: (CCTF WGPSFS)• Mr. Laurent‐Guy, METAS (Bern‐Wabern)• Dr. Tetsuya Ido, NICT (Tokyo)• Dr. Tomonari Suzuyama, NMIJ/AIST (Tsukuba)

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“The CIPM List of Recommended Frequency Standard Values:Guidelines and Procedures”,by F. Riehle, P. Gill, F. Arias, L. Robertsson,soon be on Metrologia.

Some photos

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CCL‐CCTF WGFS• The objectives of the CCL‐CCTF WGFS are:

• To make recommendations to the CCL for radiations to be used for the realization of the definition of the metre and to make recommendations to the CCTF for radiations to be used as secondary representations of the second;

• To maintain, together with the BIPM, the list of recommended frequency standard values and wavelength  values for applications including the practical realization of the definition of the metre and secondary representations of the second;

• To take responsibility for key comparisons of standard frequencies such as CCL‐K11;

• To respond to future needs of both the CCL and CCTF concerning standard frequencies relevant to the respective communities.

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frequencies for the realizations of the meterfrequencies for secondary representation of the second

Evolution in L and TF

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Length Time and Frequency

Evolution of the fractional uncertainty to realize the metre according to the miseen pratique together with two practical limitations i.e. the fractional uncertainty when measuring the length of a gauge block (dashed line) and the fractional uncertainty introduced by the diffraction correction in an interferometric length measurement (dashed – dotted line).

Evolution of the fractional uncertainty to realize the unperturbed line centre of primary atomic caesium clocks (squares) and of optical frequency standards (dots).Red dots show the fractional uncertainties of optical frequency standards  directlyrelated to the caesium atomic clock, green dots refer to published estimated standard uncertaines to realize the unperturbed line centre.

Commonly used wavelengths for the realization of the metre in dimensional metrology by interferometry

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Frequency / THz Fractional uncertainty Wavelength / nm Laser / absorber

473.612 7 1.5 x 10‐6 632.990 8 HeNeunstabilized

473.612 353 604 2.1 x 10‐11 632.991 212 58 HeNe / I2

551.580 162 400 4.5 x 10‐11 543.515 663 608 HeNe / I2

563.260 223 513 8.9 x 10‐12 532.245 036 104 2f (Nd:YAG) / I2

Secondary Representation of the Second (2017)

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Frequency / Hz Fractional uncertainty Transition Status

6 834 682 610.904 312 6 6 x 10‐16 87RbGround state hfs

Revised 2017

310 7 x 10‐16 2015 value

429 228 004 229 873.0 4 x 10‐16 87Sr neutral atom,5s2 1S0‐5s5p 3P0

Revised 2017

873.2 5 x 10‐16 2015 value

444 779 044 095 486.5 1.5 x 10‐15 88Sr+ ion,5s 2S1/2‐4d 2D5/2

Revised 2017

486.6 1.6 x 10‐15 2015 value

518 295 836 590 863.6 5 x 10‐16 171Yb neutral atom,6s2 1S0‐6s6p 3P0

Revised 2017

864.0 2 x 10‐15 2015 value

642 121 496 772 645.0 6 x 10‐16 171Yb+ ion,6s 2S1/2‐5d 2F7/2

Not revised

688 358 979 309 308.3 6 x 10‐16 171Yb+ ion,6s 2S1/2‐5d 2D3/2

Not revised

1 064 721 609 899 145.3 1.9 x 10‐15 199Hg+ ion,5d106s 2S1/2‐5d96s2 2D5/2

Not revised

1 121 015 393 207 857.3 1.9 x 10‐15 27Al+ ion,3s2 1S0‐3s3p 3P0

Not revised

1 128 575 290 808 154.4 5 x 10‐16 199Hg neutral atom,6s2 1S0‐6s6p 3P0

New 2017

• Optical frequency ratio measurement

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Present status as of 2017

Together with the direct absolute frequency measurement w.r.t.the Cs clocks, these frequency ratio measurements form an overdetermined set of data.

Two independent approaches to confirm the methods1: Least squares method to determine the “best” estimates of the frequency values by Margolis and Gill.2: Examination of closed loops in a graph theory framework by Robertsson.

115In+ transition 5s2 1S0 – 5s5p 3P0

q1 nu1 1267402452899920.0 690.0 [vonZanthier2000]

q2 nu1 1267402452901265.0 256.0 [Wang2007a]q3 nu1 1267402452900967.0 63.0

(removed because of inconsistency)[Wang2007b]

q4 nu1 1267402452901049.9 20.7 [Ohtsubo2017 accept.]

The four values available are inconsistent as Wang2007a and Wang7b have very different uncertainties but result from the same data set and there is not a clear explanation for this difference. It was decided to keep the measurement with the larger uncertainty [Wang2007a]. From the least square procedure it turned out that the uncertainty of [vonZanthier2000] is not compatible with the other data. Thus the uncertainty given in the original publication [vonZanthier2000] was increased to 690 Hz to make it statistically more consistent. [Ohtsubo2017] has an uncertainty that is more than ten times smaller than the other ones and this uncertainty was enlarged by a factor of 3 to 20.7 Hz in the calculation.

The adopted value of f(115In) is 1267402452901050 Hz uc/y = 1.6 x 10-14

CIPM 2003:

Recalculation:1267402452899920 Hz + ‐ 3.6 x 10‐13

1267402452901050.2866 Hz + ‐ 20.62 Hz

WGFSCCL-CCTF

171Yb transition 6s2 1S0 – 6s5p 3P0; latt. clock

CIPM LoF:Recalculation:

f(171Yb) = 518 295 836 590 864.0 + - 2×10-15

f(171Yb) = 518 295 836 590 863.6440 Hz +- 0.0609 Hz

The adopted value of f(171Yb) 518 295 836 590 863.6 Hz uc/y = 5 x 10-16

has been calculated by the methods presented in * with the data from the source table attached below. The estimated standard uncertainty of 5 x 10-16 takes into account the uncertainty of the 87Sr value of 4 x 10-16 governing the evaluation procedure and also takes into account the smaller database.* [Margolis, Gill 2015, Robertsson 2015, Oates 2017, Riehle et al 2017]

q24 nu8 518295836590864.0 28.0 [Kohno2009]q25 nu8 518295836590863.1 2.0 [Yasuda2012]q26 nu8 518295836590865.2 0.7 [Lemke2009]q27 nu8 518295836590863.5 8.1 [Park2013]q28 nu8 518295836590863.59 0.31 [Pizzocaro2017]q29 nu8 518295836590863.38 0.57 [Kim2017]

171Yb /87Srq70 nu8_over_nu12 1.2075070393433412 1.7e-15 [Akamatsu2014aErrata]q71 nu8_over_nu12 1.20750703934333776 2.9e-16 [Takamoto2015]q72 nu8_over_nu12 1.207507039343337749 5.5e-17 [Nemitz2016]

WGFSCCL-CCTF

WGFSCCL-CCTF

87Sr transition 5s2 1S0 – 5s5p 3P0 latt. clockq40q41q42q43q44q45q46q47q48q49q50q51q52q53q54q55

nu12nu12nu12nu12nu12nu12nu12nu12nu12nu12nu12nu12nu12nu12nu12nu12

429228004229874.0429228004229873.65429228004229873.6429228004229874.1429228004229872.9429228004229873.9429228004229872.0429228004229873.56429228004229873.7429228004229873.13429228004229873.10429228004229872.92429228004229872.97429228004229873.04429228004229872.97429228004229872.99

1.10.371.12.40.51.41.60.491.40.170.130.120.160.110.400.18

[Boyd2007] [Campbell2008] [Baillard2008] [Hong2009] [Falke2011] [Yamaguchi2012] [Akamatsu2014b] [Tanabe2015] [Lin2015][Falke2014][LeTargat2013] [Lodewyck2016] [Grebing2016(Oct14)] [Grebing2016(Jun15)] [Hachisu2017] [Hachisu2017b]

87Sr/40Ca+

q75 nu12_over_nu13 1.0442433345296416 2.5e-15 [Matsubara2012]

87Sr/87Rbq76 nu12_over_nu14 62801.453800512435 2.1e-11 [Lodewyck2016]

CIPM LoF:

Recalculation:

429228004229873.2 Hz + ‐ 5 x 10‐16

429228004229873.0356 Hz +‐ 0.047 Hz

has been calculated by the methods presented in * with the data from the source table attached below. The recommended uncertainty is the same as that of the most accurate comparison between the Cs PFS at LNE-SYRTE and PTB via an optical fibre link [Guena2017] i.e. 4 x 10-16.

• * [Margolis, Gill 2015, Robertsson 2015, Oates 2017, Riehle et al 2017]

87Sr transition 5s2 1S0 – 5s5p 3P0(update) WGFSCCL-CCTF

The adopted value of

f(171Yb) 429 228 004 229 873.0 Hz uc/y = 4 x 10-16

WGFSCCL-CCTF

40Ca+ transition 4s 2S1/2 – 3d 2D5/2 (update)

CIPM LoF:Recalculation:

f(40Ca+) = 411 042 129 776 398.4 Hz + - 1.2 x 10-14

f(40Ca+) = 411 042 129 776 399.7963 Hz ± 0.5458 Hz.

The adopted value of f(40Ca+) = 411 042 129 776 399.8 Hz uc/y = 2.4 x 10-15

has been calculated by the methods presented in * with the data from the source table attached below. Since [Chwalla2009] is not compatible with the other data, the uncertainty given in the original publication was increased to 3 Hz to make it statistically more consistent. This value has very little effect, and so the recommended frequency value comes essentially only from measurements made by two labs. Thus the final 40Ca+ uncertainty was enlarged by a factor of 2.* [Margolis, Gill 2015, Robertsson 2015, Oates 2017, Riehle et al 2017]

q56 nu13 411042129776393.2 3.0 [Chwalla2009]q57 nu13 411042129776398.4 1.2 [Matsubara2012]q58 nu13 411042129776400.5 1.2 [Huang2015,2012value]q59 nu13 411042129776401.7 1.1 [Huang2015,2014/15value]

Prediction of the timeline for redefinition of the second• On the frequency standards

• At least three different optical clocks having demonstrated validated uncertainties of about two orders of magnitude better than the Cs (few 10‐18),

• At least three independent measurements of the same optical clock in different institutes are compared,

• At least five ratios between optical frequency standards, each measured at least twice by independent laboratories and agreeing. 

• On the continuity with the present definition• At least three independent measurements of optical frequency standards w.r.t. three independent Cs primary clocks (Cs fountain uncertainties are the limitation).

• On the intervals of operation of optical clocks• Regular measurement reports over at least ten days submitted for TAI.

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A new definition should therefore take placeas early as possible and as late as necessary.

Prediction of the timeline for redefinition of the second

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3 clocks∆ / ~10 Uncertainties ~ two order of magnitude better than Cs

3 comparisons∆ / 5 10

Independent measurements of the same optical clock in different institute

3 clocks∆ / 3 10

Continuity with present definition: independent measurementsw.r.t. three independent Cs primary clocks

Regular contribution to TAI Measurement reports covering at least ten days

2 comp. b/w 5 clocks∆ / / / 5 10 Frequency ratios

Validation and decision for optical standard

CCTF Strategy Document, Annex 1 (Towards a new definition of the second in the SI, F. Riehle)

2017 2020 2022 2025 2026 20302018

CGPMCCTF CCTF CGPM CGPM

Present status as of 2017• Absolute frequency measurement

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Convergence of the absolute frequency value of the Sr clock transition after 10 years of measurements!

Continuity with present definition: independent measurementsw.r.t. three independent Cs primary clocks

CCL-CCTFWGFS

CCL-CCTF WGFS procedurefor updating the CIPM List of Frequencies

CIPM

CCTF CCL

CCL-CCTFWGFS

Copy for information

Proposals for approval of frequency standards

For information of frequency standards

For informationof practical realisations

of the metre

Submission of frequenciesfor SRS and other T/F

applications

Submission of frequenciesfor practical realisations

of the metre

Proposals for approval of practical realisations

of the metre

Towards the next CCTF• Next CCTF will be held in 2020.• Details not yet clear.• More frequency ratio data needed.• Long term operation of optical clocks needed for TAI.• More Cs fountain contribution needed. 

• (# of working Cs fountain clocks decreasing…)

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Report from TCTF/TCL JWGon Optical Frequency Metrology

Masami YasudaTime Standards Group

National Metrology Institute of Japan (NMIJ),National Institute of Advanced Industrial Science and Technology (AIST)

TCTF MeetingDelhi, IndiaXX Nov. 2017