Report from TCTF/TCL JWG on Optical Frequency Metrology

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Report from TCTF/TCL JWG on Optical Frequency Metrology Masami Yasuda 1 and Tetsuya Ido 2 1 Time Standards Group, National Metrology Institute of Japan (NMIJ), National Institute of

1 Report from TCTF/TCL JWG on Optical Frequency Metrology Masami Yasuda 1 and Tetsuya Ido 2 1 Time Standards Group, National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST) 2 Space-Time Standards Laboratory, National Institute of Information and Communcations Technology (NICT) TCTF Meeting Delhi, India 27 Nov. 2017

2 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

3 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) The CIPM List of Recommended Frequency Standard Values: Guidelines and Procedures, by F. Riehle, P. Gill, F. Arias, L. Robertsson, soon be on Metrologia. 3

4 Some photos 4

5 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. frequencies for the realizations of the meter frequencies for secondary representation of the second 5

6 Evolution in L and TF Length Time and Frequency Evolution of the fractional uncertainty to realize the metre according to the mise en 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 directly related to the caesium atomic clock, green dots refer to published estimated standard uncertaines to realize the unperturbed line centre. 6

7 Commonly used wavelengths for the realization of the metre in dimensional metrology by interferometry Frequency / THz Fractional uncertainty Wavelength / nm Laser / absorber x HeNe unstabilized x HeNe / I x HeNe / I x f (Nd:YAG) / I 2 7

8 Secondary Representation of the Second (2017) Frequency / Hz Fractional uncertainty Transition Status x Rb Revised x Ground state hfs 2015 value x Sr neutral atom, Revised x s 21 S 0 5s5p 3 P value x Sr + ion, Revised x s 2 S 1/2 4d 2 D 5/ value x Yb neutral atom, Revised x s 21 S 0 6s6p 3 P value x Yb + ion, 6s 2 S 1/2 5d 2 F 7/2 Not revised x Yb + ion, Not revised 6s 2 S 1/2 5d 2 D 3/ x Hg + ion, Not revised 5d 10 6s 2 S 1/2 5d 9 6s 22 D 5/ x Al + ion, Not revised 3s 21 S 0 3s3p 3 P x Hg neutral atom, 6s 21 S 0 6s6p 3 P 0 New

9 Present status as of 2017 Optical frequency ratio measurement 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 methods 1: 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. 9

10 115In + transition 5s 2 1 S 0 5s5p 3 P 0 q1 nu [vonzanthier2000] q2 nu [Wang2007a] q3 nu [Wang2007b] (removed because of inconsistency) q4 nu [Ohtsubo2017 accept.] CIPM 2003: Hz x Recalculation: Hz Hz WGFS CCL-CCTF 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( 115 In) is Hz u c /y = 1.6 x 10-14

11 171Yb transition 6s 2 1 S 0 6s5p 3 P 0 ; latt. clock WGFS CCL-CCTF q24 nu [Kohno2009] q25 nu [Yasuda2012] q26 nu [Lemke2009] q27 nu [Park2013] q28 nu [Pizzocaro2017] q29 nu [Kim2017] 171 Yb / 87 Sr q70 nu8_over_ e-15 [Akamatsu2014aErrata] q71 nu8_over_ e-16 [Takamoto2015] q72 nu8_over_ e-17 [Nemitz2016] CIPM LoF: Recalculation: f( 171 Yb) = f( 171 Yb) = Hz Hz The adopted value of f( 171 Yb) Hz u c /y = 5 x has been calculated by the methods presented in * with the data from the source table attached below. The estimated standard uncertainty of 5 x takes into account the uncertainty of the 87 Sr value of 4 x governing the evaluation procedure and also takes into account the smaller database. * [Margolis, Gill 2015, Robertsson 2015, Oates 2017, Riehle et al 2017]

12 87Sr transition 5s 2 1 S 0 5s5p 3 P 0 latt. clock q40 q41 q42 q43 q44 q45 q46 q47 q48 q49 q50 q51 q52 q53 q54 q55 87 Sr/ 40 Ca [Boyd2007] [Campbell2008] [Baillard2008] [Hong2009] [Falke2011] [Yamaguchi2012] [Akamatsu2014b] [Tanabe2015] [Lin2015] [Falke2014] [LeTargat2013] [Lodewyck2016] [Grebing2016(Oct14)] [Grebing2016(Jun15)] [Hachisu2017] [Hachisu2017b] q75 _over_nu e-15 [Matsubara2012] 87 Sr/ 87 Rb q76 _over_nu e-11 [Lodewyck2016] WGFS CCL-CCTF

13 87Sr transition 5s 2 1 S 0 5s5p 3 P 0 (update) CIPM LoF: Hz + 5 x WGFS CCL-CCTF Recalculation: Hz Hz The adopted value of f( 171 Yb) Hz u c /y = 4 x 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 * [Margolis, Gill 2015, Robertsson 2015, Oates 2017, Riehle et al 2017]

14 40Ca + transition 4s 2 S 1/2 3d 2 D 5/2 (update) q56 nu [Chwalla2009] q57 nu [Matsubara2012] q58 nu [Huang2015,2012value] q59 nu [Huang2015,2014/15value] WGFS CCL-CCTF CIPM LoF: Recalculation: f( 40 Ca + ) = Hz x f( 40 Ca + ) = Hz ± Hz. The adopted value of f( 40 Ca + ) = Hz u c /y = 2.4 x 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 40 Ca + uncertainty was enlarged by a factor of 2. * [Margolis, Gill 2015, Robertsson 2015, Oates 2017, Riehle et al 2017]

15 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 ), 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. A new definition should therefore take place as early as possible and as late as necessary. 15

16 Prediction of the timeline for redefinition of the second 3 clocks / ~10 3 comparisons / clocks / 3 10 Regular contribution to TAI Uncertainties ~ two order of magnitude better than Cs Independent measurements of the same optical clock in different institute Continuity with present definition: independent measurements w.r.t. three independent Cs primary clocks Measurement reports covering at least ten days 2 comp. b/w 5 clocks / / / 5 10 Frequency ratios Validation and decision for optical standard CCTF CGPM CCTF CGPM CGPM CCTF Strategy Document, Annex 1 (Towards a new definition of the second in the SI, F. Riehle)

17 Present status as of 2017 Absolute frequency measurement Continuity with present definition: independent measurements w.r.t. three independent Cs primary clocks Convergence of the absolute frequency value of the Sr clock transition after 10 years of measurements! 17

18 CCL-CCTF WGFS procedure for updating the CIPM List of Frequencies CCL-CCTF WGFS For information of frequency standards CIPM For information of practical realisations of the metre CCTF Proposals for approval of frequency standards Copy for information CCL-CCTF WGFS CCL Proposals for approval of practical realisations of the metre Submission of frequencies for SRS and other T/F applications Submission of frequencies for practical realisations of the metre

19 Towards the next CCTF Next CCTF will be held in 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 ) 19

20 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 Meeting Delhi, India XX Nov. 2017

Optical clocks as secondary frequency standards and re-definition of the second

Optical clocks as secondary frequency standards and re-definition of the second Gérard Petit BIPM Time Department ISSI Workshop Spacetime metrology, clocks and relativistic geodesy 19-23 March 2018 ISSI