Optical Lattice Clock with Spin-1/2 Ytterbium Atoms. Nathan D. Lemke

Transcription

1 Optical Lattice Clock with Spin-1/2 Ytterbium Atoms Nathan D. Lemke

2 number of seconds to gain/lose one second Clocks, past & present one second per billion years one second per million years Single ion (Al + ) Optical lattice Cesium fountain one second per thousand years one second per year one second per day Cesium beam Quartz crystal Shortt clock 10 3 Water clock Huygen s pendulum Harrison s chronometer AD roughly reproduced from ScienceNews 180(9) 2011

3 Optical Atomic Clocks Slow feedback Fast feedback 578 nm laser atomic system reference cavity fs-laser comb Ca, Sr, Hg..., Sr +, +, Ca +, Al +, Hg +... Why atoms? Identical Ageless High Q Easily isolated from environment

4 Optical Atomic Clocks 578 nm laser Very high stability reference cavity Rosenband et al., Science 319, 1808 (2008) (graph reproduced) Heavner et al., Metrologia 42, 411 (2005), current projected stability Potential for high accuracy Sr lattice ~ 1.5e-16 Al + ion ~ 9e-18 Will enable Tests of relativity Searches for variation of constants Other science: Synchrotron, radio telescopes, ultralow-noise microwaves Technology: communications, navigation

5 Key features of lattice clocks Long interaction times Large numbers (~10 4 ) narrow lines high S/N Doppler- & recoil-free Stark-free λ magic 1 S 0 3 P 0

6 Choosing the atom

7 Choosing the isotope I 0 (e.g. 87 Sr, 171, 199 Hg) I = 0 (e.g. 88 Sr, 174, 202 Hg) Boyd, et al, PRA 76, (2007) Benefits of I = 1/2 Simple sub-structure (m F = ± 1/2) Straightforward optical pumping No tensor shift Fermion no collisions? Barber, et al, PRL 96, (2006)

8 Ytterbium Energy Levels λ magic = 759 nm λ = 399 nm Δν = 28 MHz 1 P 1 λ = 556 nm Δν = 180 khz 3 P 1 3 P 0 λ = 578 nm Δν =10 mhz 1 S 0

9 Spectroscopy and Detection 1 P 1 3 P 1 3 D 1 λ = 1388 nm λ magic = 759 nm 3 P 0 Clock pulse Ground state Background Excited state 1 S 0 repump 5 ms time

10 Excitation fraction 171 Spectra Temperature ~15 μk Sideband fit Blatt, et al, PRA 80, (2009)

11 171 Spectra 3 P 0 m F = 1/2 m F =1/2 π π 1 S 0 m F =1/2 m F = 1/2 Lemke, et al, PRL 103, (2009)

12 Optical cavity design L L f f Thermal noise, vibration isolation, high vacuum, stable temperature L~30 cm Legero, et al, JOSA B 27, 914 (2010)

13 Coherence measurement Noise levels for 1 cavity Jiang, et al, Nature Photon. 5, 158 (2011)

14 Narrow lines Δν = 1 Hz Q = In-loop Open loop Interleave Dick limit 900 ms probe time 400 ms trap lifetime (1/e) Jiang, et al, Nature Photon. 5, 158 (2011)

15 Systematic uncertainty Effect Shift (10-16 ) unc. (10-16 ) Blackbody Density-dependent Lattice scalar Lattice hyper-polarizability Lattice multi-polar (M1/E2) Linear Zeeman Quadratic Zeeman Probe light AOM phase chirp Others Total Lemke, et al, PRL 103, (2009)

16 Absolute Frequency ν -171 = 518,295,836,590,865.0 ± 0.5 Hz

17 Absolute Frequency Park, et al, arxiv: ν -171 = 518,295,836,590,865.0 ± 0.5 Hz

18 Outline for the rest 1. Cold collisions of fermions 2. High-accuracy polarizability measurement Taking stock of a locked clock s tick-tock shocks from knocks and a mock hot-box - J. Sherman

19 Fermionic collisions Identical & Ultracold No s-wave scattering amplitude (quantum statistics) Small p-wave scattering amplitude (threshold at µk) Campbell et al, Science 324, 360 (2009) DeMarco et al, PRL 96, 4280 (1999)

20 Excitation Inhomogeneity Rabi frequency depends on atom temperature n, n, x y n z

21 Singlet triplet basis Swallows, et al, Science 25, 1043 (2011) Gibble, PRL 103, (2009) Lemke, et al, PRL 107, (2011)

22 Identifying p-wave collisions 1-D lattice 2-D lattice 1-D lattice b gg = 0 b eg = 74 a 0 b ee 3 = 0.1 b eg 3 s-wave only p-wave only p-wave + smaller s-wave Lemke, et al, PRL 107, (2011)

23 Canceling the collision shift Weighted mean: mhz Ludlow, et al, PRA 84, (2011)

24 Outline for the rest 1. Cold collisions of fermions 2. High-accuracy polarizability measurement Taking stock of a locked clock s tick-tock shocks from knocks and a mock hot-box - J. Sherman

25 Blackbody radiation shift 400 K 300 K 200 K

26 Electrodes Fused silica substrate Conductive & transparent ITO 2 nm Cr / 33 nm Au ~90% 760 nm

27 Electrodes Fused silica substrate Conductive & transparent ITO Set of precision ground fused silica spacers Length matched ~ 200 nm, < 1 arcsecond wedging 2 nm Cr / 33 nm Au ~90% 760 nm

28 Electrodes

29 Electrodes

30 Transmission Plate separation ECDL 760 nm Fringe center uncertainty: 50 MHz 0 10 Laser frequency (GHz)

31 Transmission Plate separation ECDL 760 nm Laser frequency (GHz)

32 Transmission Plate separation ECDL 760 nm Tuning ~17 THz (1700 fringes) Laser frequency (GHz) 1-2 ppm statistical error

33 Field Reversal

34 Measurement Results Sherman, et al, PRL 108, (2012)

35 Measurement Results Sherman, et al, PRL 108, (2012)

36 Measurement Uncertainty a b c a b c Dzuba, et al, J. Phys B 43, (2010) Porsev, et al, PRA 74, (2006) Porsev, et al, PRA 60, 2981 (1999) Sherman, et al, PRL 108, (2012)

37 Dynamic correction

38 Extracting the BBR shift Inside an ideal blackbody at 300 K Δν = 2.465(1) ΔT = 1 K causes clock uncertainty of Is this a blackbody?

39 Systematic table: update Effect Shift (10-16 ) unc. (10-16 ) Blackbody Density-dependent Lattice scalar Lattice hyper-polarizability Lattice multi-polar (M1/E2) Linear Zeeman Quadratic Zeeman Probe light AOM phase chirp Others Total ?

40 What s next for lattice clocks? level uncertainty (collisions, lattice light shifts ) Cryogenic apparatus Frequency ratios Transportable systems

41 Acknowledgements Clock Chris Oates, Andrew Ludlow, Jeff Sherman, Rich Fox, Nathan Hinkley, Kyle Beloy, Nate Phillips Frequency Comb Tara Fortier, Scott Diddams, et al Collisions (Theory) Ana Maria Rey, Javier Von Stecher Al +, Hg + Clocks Jim Bergquist, Till Rosenband, et al Sr Lattice Clock Jun Ye and his group Cs Fountain & Timescale Steve Jefferts, Tom Heavner, Tom Parker