Frequency ratios of optical lattice clocks at the 17th decimal place

Transcription

1 LEAP 2016, 12th International Conference on Low Energy Antiproton Physics March 6-11, 2016, Kanazawa, Japan Frequency ratios of optical lattice clocks at the 17th decimal place Hidetoshi Katori ERATO Innovative Space-Time Project, JST Quantum Metrology Laboratory, RIKEN Department of Applied Physics, The University of Tokyo

2 LEAP 2016, 12th International Conference on Low Energy Antiproton Physics March 6-11, 2016, Kanazawa, Japan Do you really measure frequency right? Do Cs clocks tick regularly?

3 Measure vibration of atomic pendulum as precise as possible Δtt tt 10 s 1 yr. = 10 s s (A good wrist watch) Δtt = Δνν 1 s tt νν 0 30 million yrs (Cs clock, International Atomic Time) Δtt tt = Δνν νν 0 1 s billion yrs (Optical Clocks)

4 SI unit (s, Hz) is convenient, as long as the measurement precision is not very high. (νν XX νν Cs ) 9,192,631,770 Hz. Some clocks claim uncertainty N. Huntemann, et a., Phys. Rev. Lett. 116, (2016). T. L. Nicholson, et al. Nat Commun 6, 6896 (2015). I. Ushijima, et al., Nature Photon. 9, 185 (2015). C. W. Chou, et al., Phys. Rev. Lett. 104, (2010). Ratios, such as νν aa /νν bb, are the only means to express physical quantities independent of SI unit. Find and measure meaningful quantities beyond the SI uncertainty, atomic altimetry

5 Fractional uncertainty Δνν/νν 0 The definition of a SI second Physics/Engineering with new clocks Frequency measurements with uncertainty that can not be accessed by SI second. New definition of SI second But are accessible by SR (System Riken with Sr) Current SI second

6 Atomic Clock = Atomic oscillator+ counter Atoms, molecules, and ions Detector If we assume the constancy of fundamental constants, atomic clocks would provide universal one second hνν 0 Servo control Δνν νν 0 ν Hz Quartz oscillators Lasers T. Haensch/ J. Hall (1998-) Counter Optical frequency comb We focus on atomcontrolled oscillator. Our concern: What will be the most suitable atomic system? High QQ = νν 0 /Δνν reference: optical νν 0 preferable Minize atom-container(trap) interactions (Accuracy) Many atoms NN to reduce quantum noise as 1/ NN (Stability)

7 Our approach Andrews): Designing novel atom traps that simulate Paul trap Millions of neutral atoms in an optical lattice allows: No collision shifts No Doppler shifts Similar to Paul trap Long interaction time N atoms: S/N ~ N 1/2, simulates millions of ion clocks operated in parallel; to measure N times faster A Magic to avoid light shift perturbation: XXXXXXXXX hhhh = hhνν 00 αα ee ωω mm αα gg ωω mm 22 EE 22 ΔΔββ ωω mm EE 44 ΔΔαα ωω mm = αα ee ωω mm αα gg ωω mm = 00: magic frequency Lattice potential Total energy Clock transition Essence: Control perturbation just by frequency, which is best describable. Hyperpolarizability effects: ΔΔββ ωω mm EE 44 can be level; Syrte,(2006), NIST(2006) 2λ L Katori, FSM 2001: key ingredient: use of scalar states so that light shift solely depend on frequency 7

8 Optical lattice clocks in the world LUH(Mg) VNIIFTRI (Sr) NPL(Sr) SYRTE(Sr,Hg) KL FAMO(Sr) KRISS(Yb) PTB(Sr) AIST(Yb) NIM(Sr) Tokyo(Sr,Yb,Hg) HHU(Yb) SIOM(Hg) LENS(Sr) ECNU(Yb) NICT(Sr) INRIM(Yb) The most recent measurents on Sr: X. Baillard et al., Eur. Phys. J. D 48, 11 (2008). G. K. Campbell et al., Metrologia 45, 539 (2008). F. L. Hong et al., Opt. Lett. 34, 692 (2009). A. Yamaguchi, et al., Appl. Phys. Exp. 5, (2012). Le Targat, R. et al., Nat Commun. 3109, 4 (2013). S. Falke et al., New J. Phys. 16, (2014). JILA: Ludlow, et al., PRL 96, (2006) Tokyo-NMIJ: Takamoto, et al., J. Phys. Soc. Jpn. 75, (2006). SYRTE: Targat, et al., PRL 97, (2006). S. Falke et al., New J. Phys. 16, (2014). NIST( 171 Yb) JILA(Sr) RECOMMENDATION Sr CIPM ( ) Yb νν 8888SSSS = Hz with relative standard uncertainty of 5 x (SI second uncertainty) Alternatively, present SI second cannot allow sharing further digits of Sr clock frequency. Needs for a better definition of a second 8

9 OUTLINE: THE REAL CHALLENGE FOR A CLOCK IS TO MEASURE SOMETHING USEFUL! Sr-Sr Hg/Sr Yb/Sr Sr(RIKEN)-Sr(UT) Sr How far can we go? Collective effects Sr Blackbody radiation shift: reference Frequency ratio R, Constancy of constants Hg Frequency matrix for redef. SI second Relativistic geodesy Operational Yb magic Sr(UT) frequency to explore Collectively coupled into a fibre To go beyond the SI-second... compare two clocks 9

10 Optical lattice relies on ac Stark shift Large polarizability with NIR/VIS light is good for trapping of atoms, but it causes non-negligible BBR shift; essential tradeoffs in optical lattice clocks REDUCTION OF BBR SHIFT: CRYOCLOCK 10

11 . Blackbody radiation shift was expected to be one of the major sources of uncertainties since proposal. We did not dream of installing a refrigerator, as uncertainty was so far away in

12 BBR: Experimentalist's calculation in 2003 Polarizability Polarizability αα (arb. unit) αα(3pp 0 ) αα(1ss 0 ) BBR@300K 3 PP 0 3 DD Magic nm Frequency (Hz) (Hz) 3 1 PP 0 2 αα PP(ωω)EE 2 1 SS αα SS(ωω)EE 2 3 PP 0 state is more sensitive to BBR Engineered equal light shift by the magic wavelength Blackbody radiation spectrum: uu νν = 8πππνν3 1 (Planck s law) cc 3 ee hνν/kkkk 1 Energy density of BBR: EE 2 8ππ = 0 uu νν dddd = 5 4 kk BB 15cc 3 εε 0 h 3 TT4 = cc 1 TT 4 (Stefan Boltzmann) δδνν BBBBBB TT 1 αα 2h PP 0 αα SS 0 EE 2 = 1 Δαα(0)cc 2h 1TT 4 (approx. by DC polarizability)

13 BBR: Experimentalist's calculation in 2003 Polarizability Polarizability αα (arb. unit) αα(3pp 0 ) BBR@300K BBR@70K αα(1ss 0 ) 3 PP 0 3 DD Magic nm Frequency (Hz) (Hz) 3 1 PP 0 2 αα PP(ωω)EE 2 1 SS αα SS(ωω)EE 2 3 PP 0 state is more sensitive to BBR Engineered equal light shift by the magic wavelength Blackbody radiation spectrum: uu νν = 8πππνν3 1 (Planck s law) cc 3 ee hνν/kkkk 1 Energy density of BBR: EE 2 8ππ = 0 uu νν dddd = 5 4 kk BB 15cc 3 εε 0 h 3 TT4 = cc 1 TT 4 (Stefan Boltzmann) δδνν BBBBBB TT 1 αα 2h PP 0 αα SS 0 EE 2 = 1 Δαα(0)cc 2h 1TT 4 (approx. by DC polarizability)

14 Cryogenic optical lattice clocks with 87 Sr Towards the realization of clock accuracy δδδδ νν 0 < Blackbody radiation (BBR) shift: δδνν BBR 2.1 K Temperature need to be measured with 20 mk ucertainty Development of cryogenic Sr clocks with cold chamber EE 2 TT 4 δδνν BBR = (1 2)ΔααEE 2 TT 4 Ø 1.0 mm δδνν BBR 23 K Control of BBR at possible 19.6 mm typ. 7 mm Sr Ø 0.5 mm Sr

15 Direct measurement of BBR shift on Sr clock THz mm Excitation rate (a.u.) Clock K Clock K Δf = 2 Hz 8 mm Clock 1 (300K) Clock 2 (300K) Clock laser frequency (Hz) Δf = 2 Hz with 400 ms ππ pulse Rabi spectrum

16 Direct measurement of BBR shift on Sr clock THz 24 mm 1.0 Excitation rate (a.u.) Clock K Clock 1 95 K 8 mm Clock 1 (95K) Clock 2 (300K) Clock laser frequency (Hz) Δf = 2 Hz with 400 ms ππ pulse Rabi spectrum

17 Temperature dependence of BBR shift Operating temp. at 95K Dynamic contribution Temperature dependence of BBR shift Δνν BBR TT = Δνν stat TT TT Δνν dyn TT TT ΟΟ TTTT0 8 total shift TT 1 (Sr1) : constant at 95 K TT 2 (Sr2) : changing from 95 K to 300 K Measure the frequency difference of δδ BBR = νν TT 2 νν TT 1 ref. DC polarizability measurement (PTB): T. Middelmann et al., PRL 109, (2012) Ushijima, Takamoto, Das, Ohkubo, Katori, Nature Photon. 9, 185 (2015). νν dyn (this work: blue) : (26) mhz νν dyn (PTB: red) : (23) mhz

18 Two cryogenic Sr clocks agreed with Speedy operation to reach σ yy ~ within 2 hours averaging cf. Single ion clock: ~10 days averaging to reach BBR shift unc Agreement & reproducibility of two clocks at δδνν νν 00 = ( ± ± ) stat. sys. mainly due to lattice light shift (later) Ushijima, Takamoto, Das, Ohkubo, Katori, Nature Photon. 9, 185 (2015).

19 More clocks needed to access physics For identical atomic clock comparison, we know the answer to be one. The ratio, such as, RR = νν Hg νν Sr, νν Yb νν Sr, nobody knows the answer now, but can be testable in the future. 1) Ratios may test constancy of αα = ee2 4ππεε 0 ħcc : ΔRR RR (νν Hg νν Sr ) = 0.75 Δαα αα ; ΔRR RR (νν Yb νν Sr ) = 0.25 Δαα αα e.g. Oscillation of αα: K. Van Tilburg, N. Leefer, L. Bougas, and D. Budker, Search for Ultralight Scalar Dark Matter with Atomic Spectroscopy, Phys. Rev. Lett. 115 (2015). 2) Making ratio matrix may test the consistency of optical clocks toward future redefinition of the second 3) Real time geopotentiometry using gravitational red shift 19

20 Cryogenic Yb/Sr compatible clock clock laser 578nm lattice phase stabilization phase stabilization Sr/Yb share similar properties, in wavelengths, oven temperatures, allowing to build compatible clocks for both species. Zeeman slower 96K cryo - chamber 20 mm transport to CCD Contribution Shift (mhz) Unc. (mhz) BBR shift at 96 ± 0.3 K MOT lasers Room temp. leakage / 556 nm Reflections Total

21 Cryogenic Yb/Sr clock comparison Yb/Sr Sr Er fiber comb from NMIJ: Iwakuni et al., Opt. Exp. 20, (2012) 21

22 Synchronous ratio ( νν Yb νν Sr ) measurement Individual clock stability limited by (aliased) laser noise Bize, IEEE TUFFC (2000) Takamoto, Nat. Photon (2011) Synchronous interrogation Common mode noise does not degrade ratio measurement best observed stability t i = 200 ms t cyc = 1.5 s P Sr(429T) Yb(518T) Time

23 Ratio of Yb/Sr clock frequencies Reference values: NIST/JILA: Lemke et al., PRL 103, (2009). Campbell et al., Metrologia 45, 539 (2008) CIPM: CIPM Recommendation 1(CI-2013) NMIJ ratio: Akamatsu et al., Opt. Exp. 22, 7898 (2014) RIKEN2014: Takamoto et al., C. R. Phys. 16, 489 (2015) R Yb/Sr = (43) sys (35) stat (uncertainty: ) competitive to Al+/Hg+, T. Rosenband, et al., Science 319, 1808 (2008). N. Nemitz, et al., arxiv: (2016). Appeared in nature photonics online.

24 Hg optical lattice clocks Sr Hg Measure non-zero physical quantities Small blackbody radiation (BBR) shift accuracy and stability at room temperature. High sensitivity αα 2 ZZ 2 to the variation of fine-structure constant αα = ee2 4ππεε 0 ħcc 1 3 jj+1/2 Dirac theory: EE nn,jj = ZZ2 RRRR 1 + αα2 ZZ 2 nn 2 nn ΔRR/RR 0.75Δαα αα by referencing Sr clocks. Difficulties in developing Hg optical lattice clocks RR νν HHHH = νν SSSS with δδδδ RR = K. Yamanaka, et al., Phys. Rev. Lett. 114, (2015). 4nn + OO(αα4 ZZ 4 )

25 Importance of frequency ratio measurements Hg (1 d) Al (2 d) Although optical clocks claim uncertainties... limited by SI second (CIPM recommendation) Yb (500 s) Sr (1 d) Cs (20 d) Sr ( s) Hg ( s) Yb (30 d) Ca (100 s) Lorini et al., Eur. Ph. J. Sp. Top. 163, 19 (2008). C. W. Chou, et al., Phys. Rev. Lett. 104, (2010). G. Barwood, et al., Phys. Rev. A 89, (2014). T. L. Nicholson et al., Nat Commun 6, 6896 (2015). Godun et al., arxiv: v2 (2014). 25

26 Importance of frequency ratio measurements NIST Yb:? Yb (500 s) σ = (NMIJ) σ = (RIKEN) Sr ( s) Hg (1 d) σ = (NIST) Cs (20 d) Al (2 d) Sr (1 d) Ca (100 s) Optical clock comparisons allow going beyond SI limit. Once νν Sr is measured by SI, ratio RR = νν XX /νν Sr allow, connecting optical clocks νν XX to SI, as νν XX =RR = νν XX νν Sr (SI) νν Sr Bonus: Fundamental constants vary? σ = (RIKEN) Hg ( s) Yb (30 d) sources: Cs : BIPM circular T Hg+ : Lorini et al., Eur. Ph. J. Sp. Top. 163, 19 (2008) Al+ : (Talk Tue), Chou et al., PRL 104, (2010) Sr+ : (B15), Barwood et al., PRA 89, (R) (2014) Ca+ : Matsubara et al., Opt. Exp. 20, (2012) Yb+ : (Talk Tue), Huntemann (PhD thesis) 26 Yb, Sr, Hg: RIKEN clocks

27 Lattice light shift dominates uncertainty budgets

28 How far can we go with lattice? At level, E1 polarizability approximation is no longer true; M1, E2, hyperpolarizability gives non-linear light shift: Operational magic frequency to reduce lattice shift to ~10 19 for certain range of lattice intensity (30-50%) E B x Magnetic field amplitude z Electric field amplitude E B y 28

29 height reference point Disseminations of clock signal are crucial for establishing new standards, revealing gravitational potential differences of ħδωω = mmggδh ħωω 0 mmcc 2 18 Δh = cm QUANTUM BENCHMARK: CLOCK APPLICATIONS IN THE FUTURE Lisdat, C. et al. A clock network for geodesy and fundamental science. arxiv: (2015). PTB-SYRTE clocks of 700-km-apart 29

30 Akatsuka, T. et al., Jpn. J. Appl. Phys. 53, (2014). P. A. Williams, W. C. Swann, and N. R. Newbury, J. Opt. Soc. Am. B 25, 1284 (2008). Connecting Sr clocks at UT and Riken using 30-km-long fiber μμμ Fiber loss (measured) 30.4 nm 23.7 nm Transfer 698x2=1396 nm laser through telecom fiber No frequency combs necessary; Clock comparison is not limited by comb stability Long distance link would be possible by employing OH-free fiber Riken 15 km (30 km fiber) UT

31 The team: Sr clocks: I. Ushijima, M. Das, M. Takamoto Hg clock: K. Yamanaka, T. Pruttivarasin, N. Ohmae Yb clock: N. Nemitz, T. Ohkubo Fiber Link: T. Akatsuka Sr clock (UT): T. Takano, A. Yamaguchi HC fiber: S. Okaba, F. Benabid UV Lasers, combs: Y. Kaneda, H. Inaba, F.-L. Hong Theory: V. D. Ovsiannikov, S. I. Marmo, V. G. Palchikov 31 Riken Campus at Wako, April, 2015

32 Summary Cryogenic Sr/Yb and Hg clocks in operation A first optical-lattice-clock frequency matrix is done with (4.6 Yb Sr 8.4 Hg/Sr ) Non-linear light-shift analysis with Operational magic frequency will allow light shift uncertainty Gravitational potential meter over 15 km with Power of synchronous interrogation: Possible search of transient-in-time Δαα/αα with Hg/Sr or Yb/Sr, and temporal variation of gravitational potential diff. Use of cooperativity in the future optical lattice clocks

33 We look for something to measure up to 18 th decimal places. If you know, let us know! 33