Stationary 87 Sr optical lattice clock at PTB ( Accuracy, Instability, and Applications)

Transcription

1 Stationary 87 Sr optical lattice clock at PTB ( Accuracy, Instability, and Applications) Ali Al-Masoudi, Sören Dörscher, Roman Schwarz, Sebastian Häfner, Uwe Sterr, and Christian Lisdat

2 Outline Introduction Stationary clock Local comparison (Yb + ) Remote comparison (Paris) Summary 2

3 Atomic clocks interrogation T i oscillator ν osc t atomic reference ν 0 clock cycle correction detection frequency offset Δν stable frequency output 3

4 polarisability / arb. u. 87 Sr lattice clock (5s6s) 3 S 1 1 S 0-3 P 0 clock transition (ν THz). Γ 2π 1 mhz in fermionic 87 Sr (I = 9/2). (5s5p) 1 P 1 Optical lattice at magic wavelength: Differential light shift cancelled. Shifts due to atomic motion suppressed (Lamb Dicke regime). (5s5p) 3 P J 698 nm (clock) J = 2 J = 1 J = 0 3 P 0 3 D 1 3 P 0 3 S 1 (5s 2 ) 1 S 0 magic wavelength (λ m 813 nm) lattice frequency / THz 4

5 Stationary clock (5s6s) 3 S 1 (5s5p) 1 P ms Zeeman slower 1 st stage MOT (461 nm) 90 ms 50 ms 2 nd stage MOT (689 nm) 3 rd stage MOT (689 nm) 461 nm J = 2 65 ms transfer to 1D lattice & state preparation (m F = ±9/2) 689 nm J = 1 J = 0 (5s5p) 3 P J 600 ms interrogation (698 nm) 698 nm (clock) detection n = n 0 ± dn (5s 2 ) 1 S 0 Lattice orientation: horizontal (θ 0.12 ) Atom number: < 1000 Temperature: < 1 µk (ax.) / < 2 µk (rad.) Cycle duration: ca. 1 s 5

6 Sr-1: Systematic uncertainty u syst Limiting factors: Temperature gradients (blackbody radiation) Lattice orientation (tunnelling vs. light shifts) effect correction (in ) uncertainty (in ) BBR, ambient BBR, oven lattice, scalar+tensor lattice, E2/M1 pol lattice, hyperpol tunneling AOM efficiency servo error Zeeman, 2 nd order cold collisions DC Stark shift probe light line pulling optical path length total

7 temperature / C Blackbody radiation shift T T T n BBR n dc( T0 ) n ( 4 dyn T0 ) O 6 8 T 0 T0 T0 atomic response to BBR BBR (Temperature) Uncertainty Temperature gradient n dc ( T 0 ) mk n dyn ( T 0 ) T. Middelmann, et al., Phys. Rev. Lett., 109, (2012) T. Nicholson, et al., Nature Com. 6, 6896, (2015) 06:00 12:00 18:00 00:00 06:00 12:00 time

8 Blackbody radiation shift ylindrical copper Parameters: Copper Outer diameter= 32 mm Inner diameter = 10 mm Length = 83.2 mm Orifice radius = 0.5 mm Graphite tube BK7 Glass Graphite Outer diameter = 10 mm length = 50 mm 20mm 8

9 Blackbody radiation shift Transport distance = ( ) mm Transport time = 350 ms 20mm 9

10 frequency shift (MOT - CF) / Hz Blackbody radiation shift 0 Accuracy 8-9 * possible :00 14:00 17:00 20:00 time 10

11 Instability Instability 11

12 y ( ) Instability ( ) y n n 1 N T C averaging time (s) 12

13 Allan deviation Instability Cs fountain clock Yb + single ion few s 10 3 s 10 6 s Sr lattice clock averaging time (s) 13

14 Noise analysis: total Allan deviation Instability Detection limited by QPN for > 130 atoms. Aliased laser noise still dominant (Dick effect). Predicted interleaved instability matches observation. Best published instability for normal operation! σ y (τ) = (τ/s) -1/2 A. Al-Masoudi et al., Phys. Rev. A 92, (2015) excitation probability noise pe QPN Electronic noise All without laser noise Shot noise g + e 2o (counts) averaging time (s) 14

15 excitation Probability excitation probability excitation Probability Instability From Rabi to Ramsey Scan Hz Δν scan Hz scan Hz 15

16 sensitivity function g(t) Instability Multi Ramsey Normal Ramsey 1 p g( t) n ( t) t Normal Ramsey Multi Ramsey time (ms) 16

17 excitation probability excitation Probability Instability Multi Ramsey Normal Ramsey 1.0 Theory Data scan (Hz) scan Hz 17

18 excitation probability Instability Multi Ramsey Normal Ramsey applied frequency (Hz) 18

19 reconstructed phase ( ) sensitivity function g(t) Instability Multi Ramsey Normal Ramsey Multi Ramsey Normal Ramsey applied frequency step (Hz) t / ms 19

20 Applications Applications 20

21 Local clock comparison: 171 Yb + / 87 Sr PTB s 171 Yb + single-ion clock: Electric-octupole (E3) transition ( 2 S 1/2 2 F 7/2, ν THz) systematic uncertainty Instability of (τ/s) -1/2 N. Huntemann, High-Accuracy Optical Clock Based on the Octupole Transition in 171 Yb +, PhD thesis, LU Hannover (2014) Frequency ratio sensitive to variations of α: 171 Yb + clock highly sensitive. 87 Sr clock insensitive. ΔR/R -6 Δα/α V.V. Flambaum and V.A. Dzuba, Can. J. Phys. 87, 25 (2009) 21

22 Local clock comparison: 171 Yb + / 87 Sr Measurement in 2015: > 80 h of data acquired. Instability of (τ/s) -1/2. Statistical uncertainty Total uncertainty PRELIMINARY 22

23 Variations of the fine-structure constant α Measurement in 2015: > 80 h of data acquired. Instability of (τ/s) -1/2. Statistical uncertainty Total uncertainty PRELIMINARY courtesy of: Nils Huntemann Drift measurement: Combine ratio measurements from 2012 and Uncertainty improved by factor 4! Sr/Yb PTB (preliminary): (1/α) (dα/dt) = (7±5) / yr Al + /Hg NIST: (1/α) (dα/dt) = (16±23) / yr T. Rosenband et al., Science 319, 1808 (2008) 23

24 Remote clock comparison Collaboration of PTB with participation of the Réseau National de télécommunications, the Institut für Erdmessung of the Leibniz Universität Hannover, and the Laboratoire Photonique, Numérique et Nanosciences. Paris Braunschweig 24

25 Remote clock comparison Satellite link (TWSTFT, GPS) Paris Braunschweig 25

26 Remote clock comparison Satellite link: Few uncertainty Long averaging times ( weeks) Difficulties due to satellite motion and atmosphere. Satellite link (TWSTFT, GPS) Paris Braunschweig 26

27 Remote clock comparison Satellite link: Few uncertainty Long averaging times ( weeks) Difficulties due to satellite motion and atmosphere. Satellite link (TWSTFT, GPS) Paris Telecom fibre link Braunschweig 27

28 Remote clock comparison Satellite link: Few uncertainty Long averaging times ( weeks) Difficulties due to satellite motion and atmosphere. Telecom fibre link: Uncertainties far below Short averaging times ( ~ minutes) Satellite link (TWSTFT, GPS) Paris Telecom fibre link Braunschweig 28

29 Frequency transfer link across 690 km Ch. Lisdat et al., arxiv: (2015) PTB OP 29

30 total Allan deviation y ( ) First remote clock comparison Ch. Lisdat et al., arxiv: (2015) st campaign 2 nd campaign link averaging time (s) precision after 1000 s of averaging. 10 better 10,000 faster 30

31 total Allan deviation y ( ) First remote clock comparison Ch. Lisdat et al., arxiv: (2015) st campaign 2 nd campaign link averaging time (s) precision after 1000 s of averaging. 10 better 10,000 faster Uncertainty limited by clocks! Contribution uncertainty (in ) systematic, Sr(OP) 4.1 systematic, Sr(PTB) 1.9 statistical 2 fs combs 0.1 link 0.03 gravity potential 0.4 total

32 total Allan deviation y ( ) Sr PTB / Sr SYRTE 1 First remote clock comparison Ch. Lisdat et al., arxiv: (2015) st campaign 2 nd campaign link averaging time (s) precision after 1000 s of averaging. 10 better 10,000 faster date of measurement (MJD 57092) Agreement within combined uncertainty of clocks ( ). First comparison of remote clocks at the level! 32

33 total Allan deviation y ( ) excitation probability frequency shift (MOT - CF) / Hz Summary 0 Accuracy :00 14:00 17:00 20:00 time 1.0 Instability applied frequency (Hz) Applications More averaging time (s) 33

34 Thank you for your attention. Ali Al-Masoudi Physikalisch-Technische Bundesantalt Working Group 4.32 Optical Lattice Clocks Bundesallee 100 D Braunschweig Germany phone: web: 34