Stable & Accurate Single- - Stable & Accurate Single atom - PowerPoint PPT Presentation

Stable & Accurate Single- - Stable & Accurate Single atom Optical Clocks atom Optical Clocks Ti:Saph Fs-comb group: The Masters: Al+ Ion Group: Jason Stalnaker Wayne Itano Tara M. Fortier Till Rosenband Dave Wineland Kyoungsik Kim Piet Schmidt* Scott A. Diddams James Chou Hg+ Ion Group: Leo Hollberg David Hume Anders Brusch Fiber Fs-comb Group: Cs Clock Group: Luca Lorini Windell Oskay Ian Coddington Steve Jefferts Brent Young Bill Swann Tom Heavner Rob Rafac Nate Newbury Liz Donley Carol Tanner Tom Parker JILA Robert Drullinger Jun Ye et al. * funded by:

What is a clock? An Oscillator A Counter (Generates periodic events) (Counts and displays events) 2

Optical Clock Laser 1121 THz fs-comb Oscillator 10:24am frequency feedback State Detector Single Ion/ Neutral Atom Frequency standard

Clock stability Quantum projection noise limit: Example 1 : Cesium fountain clock Atom Number: Expected Stability: Transition Frequency: Interrogation time: Example 2: Mercury ion optical clock Atom Number: Expected Stability: Transition Frequency: Interrogation time: • Higher stability, even with only one atom! Potentially high accuracy. 5

Outline • Al + /Hg + clock transitions & spectroscopy • Systematic uncertainties • Comparisons • Implications & future directions

199 + Hg Energy Levels Metastable state 194 nm 194 nm 282 nm 282 nm Wide, fast transition Laser cooling, detection Clock reference; Narrow (“forbidden”) transition Quantum Jump spectroscopy ( Electron Shelving) 7

Quantum Jump Spectroscopy The mercury ion acts as a noiseless, optical amplifier One absorption event can prevent millions of scattering events Excited state Ground state 80 Counts/ms 60 40 20 0 0 200 400 600 800 Time (ms) 9

Spectroscopy of 27 Al + • 8 mHz linewidth clock transition 1 P 1 • Insensitive to external fields 3 P 0 • Smallest known room temperature 167 nm blackbody shift [2] 267 nm • No accessible strong transition for 1 S 0 cooling & state detection • Use two-ion quantum logic techniques with 9 Be + and 27 Al + for cooling, state preparation & readout Be + Al + [1] [1] D.J. Wineland et al. , Linear Paul Proc. 6th Symposium on Trap Frequency Standards and [2] T. Rosenband et al. arXiv:physics/0611125 Metrology, 2001, pp. 361-368

Normal modes z Be + Al + x Linear Paul Trap Center-of-mass (COM) 2.62 MHz Stretch 5.8 MHz xAl 3.5 MHz xBe 13.0 MHz

Clock state transfer to Be + Be + RSB Al + 3 P 1 BSB initial state detection 3 P 1 F=1 n=1 X n=0 X X 1 S 0 F=2 n=1 X n=0 Be + Be + Al + Be + Is Al + in the 1 S 0 or 3 P 0 state? 1. Ground state cooling (1 ms) P.O. Schmidt, et al. 2. Al + 3 P 1 blue sideband (BSB) pulse (30 us) Science 309 , 749 (2005) 3. Be + F=2 → F=1 red sideband (RSB) pulse (7 us) T. Rosenband, et al. arXiv:physics/070367 4. Be + detection (200 us), record photon counts (accepted by PRL) 5. Al + 3 P 1 spontaneous decay

Detection outcomes 0.8 0.14 3 P 0 1 S 0 0.7 0.12 Mean = 6.9 Mean = 1.3 0.6 0.1 0.5 Probability ility 0.08 b a 0.4 b Transitions detected in both directions ro 0.06 P 0.3 0.04 0.2 0.02 0.1 0 0 0 10 20 0 10 20 PMT counts 99.94% Detection fidelity D. B. Hume, et al. To be published

Rabi Spectroscopy 100 ms probe time 1 50 scans 0.8 Transition probability 8.4 Hz 0.6 0.4 0.2 0 -20 -15 -10 -5 0 5 10 15 20 Frequency offset [Hz] near 1121 THz 1 Transition prob. 0.5 0 0 1 2 3 4 5 6 7 8 9 10 11 Pulse duration [ms]

Trapped ions in an rf trap • No static E or B fields; Trap acts on total charge of ion, not internal structure • Trap ion at trap center where trapping fields approach zero ~ rf • Can operate in tight-confinement (Lamb-Dicke) regime ⇒ First-order doppler free. 2nd-order doppler shift (time dilation) due to micromotion will limit accuracy 11

Cryogenic ion trap system Magnetic Shield 12

Cryogenic ion trap system Magnetic Shield Cryostat Wall 12

Cryogenic ion trap system Magnetic Shield Cryostat Wall 77 K Shield 12

Cryogenic ion trap system Magnetic Shield Cryostat Wall 77 K Shield 4 K Copper Shield around trap 12

Liquid Nitrogen Magnetic Shield Cryostat Wall 77 K Shield Liquid Helium • Long storage times Helical Resonator • Environmental isolation - Low collision rate 4 K Copper Shield - Low blackbody around trap 13

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Trap material: molybdenum 0.8 mm 14

12 MHz, 1 kV ~ RF Secular Frequency: 15

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Detection Cooling, 194 nm 16

Fused silica lens in cryostat for state detection Cooling, Detection 17

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Clock Probe Beam 282 nm 18

Absorption lineshape in 199 Hg + • Quantum jump spectroscopy 1.0 - Single pulse (Rabi) Excitation 6.7 Hz P g - Transform-limited linewidth • Lock laser to center of absorption line 0.5 Next: Measure frequency! Probe time: 21

Al + /Hg + Comparison • fs-comb locked to Hg + f Hg /4 f Al /4 • measure beat with Al + 3 P 0 2 D 5/2 2 S 1/2 1 S 0 199 Hg + [1] 27 Al + [1] W. H. Oskay, et al. PRL 97, 020801 (2006)

Al + /Hg + Stability 29096 seconds of data -13 10 7 × 10 -15 τ -1/2 Hg vs Maser (AVAR) Hg vs Al (AVAR) Hg vs Al (THEO1) -14 10 Δν / ν -15 10 R e c e n t l 4 x 10 -17 y : 4 x 1 0 - 1 5 τ - 1 / 2 -16 10 -17 10 0 1 2 3 4 5 10 10 10 10 10 10 time [seconds]

Al + /Hg + Comparison First comparison of frequency standards 15 - 1 052 871 833 148 000 at the 17 th digit. 990.5 10 -16 fAl / fHg * 10 990.4 Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar 2007 2006

27 Al + error budget Shift Uncertainty Effect Parameter [ x 10 -17 ] [ x 10 -17 ] Operating Blackbody shift -1.2 0.5 temperature Micromotion 2 nd order Doppler Axial RF field -0.3 0.3 Micromotion 2 nd order Doppler Radial static field -2 2 Secular 2 nd order Doppler Radial temperature -2 1.5 2 nd order Zeeman RMS magnetic field -68.4 0.1 Be + cooling laser Stark shift I / Isat -0.7 0.3 1 st -order Doppler from 0 1 correlated ion movement Total -74.6 2.8

Self-referenced frequency comb ( not to scale!) Frequency comb Phase-coherent frequency division 26

~ Stable Hydrogen Mercury ion NIST-F1 Frequency comb Laser Masers

Systematic Frequency Shifts • The immediate future: Begin averaging over quadrupole shift Error budget: Estimated partial error budget for the near future Correction (Hz) Fractional uncertainty Effect (10 -15 ) (at 1.06 PHz) Second-order Zeeman 1.19 <0.01 (B field uncertainty) quadrupole shift 0 0.01 Gravitational redshift 0.55 0.01 Micromotion shifts 0 0.01 Expected fractional systematic uncertainty: ~2 x 10 -17 32

Present and future work • Absolute frequency measurements (vs cesium) - Aim for fractional uncertainty below 10 -15 • Optical-optical clock comparisons - Compare vs Hg + (second system), Ca, Sr, Yb, Al + - Improve understanding of systematics - Test of stability of fundamental constants • Improvements to reliability & stability: - Solid-state laser systems - Add laser to quench (de-excite) state 33