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Atomic Clocks for New Physics Searches - Indico How atomic clocks work Applications of atomic clocks

Aug 06, 2020

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  • Atomic Clocks for New Physics Searches

    Marianna Safronova

    New Physics oN the Low-eNergy PrecisioN FroNtier, cerN

    Department of Physics and Astronomy, University of Delaware, Delaware, USA Joint Quantum Institute, NIST and the University of Maryland, College Park, Maryland, USA

  • GPS satellites: microwave atomic clocks Accuracy: 0.1 ns

    airandspace.si.edu

    Optical atomic clocks will not lose one second in 30 billion years

    0hν

    0E

    1E

    0

    1

  • What dark matter affects atomic energy levels?

    What dark matter can you detect if you can measure changes in

    atomic/nuclear frequencies to 20 digits?

    0ν is a clock frequency0hν 0E

    1E

    0

    1

  • Outline

     How atomic clocks work  Applications of atomic clocks  How good is the clock: stability and uncertainty  Dark matter searches with clocks - oscillatory and transient signals  Future clock progress

    • Improvement of current clocks • Highly charged ion clocks • Nuclear clock

     Projected sensitivity of a nuclear clock to relaxion searches

  • Ingredients for a clock 1. Need a system with periodic behavior:

    it cycles occur at constant frequency

    NOAA/Thomas G. Andrews

    2. Count the cycles to produce time interval 3. Agree on the origin of time to generate a time scale

    Ludlow et al., RMP 87, 637 (2015)

  • Ingredients for an atomic clock

    1. Atoms are all the same and will oscillate at exactly the same frequency (in the same environment): You now have a perfect oscillator!

    2. Take a sample of atoms (or just one)

    3. Build a laser in resonance with this atomic frequency

    4. Count cycles of this signal

    Ludlow et al., RMP 87, 637 (2015)

    171Yb+ ION

    0hν

    0E

    1E

    0

    1

  • How optical atomic clock works

    The laser is resonant with the atomic transition. A correction signal is derived from atomic spectroscopy that is fed back to the laser.

    From: Poli et al. “Optical atomic clocks”, La rivista del Nuovo Cimento 36, 555 (2018) arXiv:1401.2378v2

    An optical frequency synthesizer (optical frequency comb) is used to divide the optical frequency down to countable microwave or radio frequency signals.

    0hν

    0E

    1E

    0

    1

    The laser is resonant with the atomic transition. A correction signal is derived from atomic spectroscopy that is fed back to the laser.

  • Extraordinary progress in the control of atomic systems 300K

    nK TrappedUltracold

    3D

    Image: Ye group and Steven Burrows, JILA

    Precisely controlled

  • Strontium optical lattice neutral atom clock

    http://www.nist.gov/pml/div689/20140122_strontium.cfm

    4f146s 2S1/2

    4f136s2 2F7/2

    467 nm

    E3

    E2 435 nm

    4f145d 2D3/2

    Yb+ single trapped ion clock

    Yb+ PTB

    Mg Al+ Cd Sr Yb Hg

    Neutral atoms in optical lattice vs. a single trapped ion

    10 years

  • Applications of atomic clocks

    Image Credits: NOAA, Science 281,1825; 346, 1467, University of Hannover, PTB, PRD 94, 124043, Eur. Phys. J. Web Conf. 95 04009

    GPS, deep space probes

    Very Long Baseline Interferometry Relativistic geodesy

    Quantum simulation Searches for physics beyond the

    Standard ModelDefinition of the second

    10 -18 1 cm height

    Gravity Sensor

    Magma chamber

  • Atomic clocks can measure and compare frequencies to exceptional precisions!

    If fundamental constants change (now) due to for various “new physics” effects atomic clock may be able to detect it.

    Search for physics beyond the standard model with atomic clocks

    Frequency will change BEYOND THE

    STANDARD MODEL? 0hν

    0E

    1E

    0

    1

  • Searches for physics beyond the Standard Model with atomic clocks

    Dark matter searches

    Search for the violation of Lorentz invariance

    Tests of the equivalence principle

    Are fundamental constants constant?

    α Gravitational wave detection with atomic clocks PRD 94, 124043 (2016)

    Image credit: NASA

    Image credit: Jun Ye’s group

  • RMP 90, 025008 (2018)

  • http://www.nist.gov/pml/div689/20140122_strontium.cfm

    JILA Sr clock 2×10-18

    • Table-top devices • Quite a few already constructed,

    based on different atoms • Several clocks are usually in one place • Will be made portable (prototypes exist) • Will continue to rapidly improve • Will be sent to space

    Clocks: new dark matter detectors

  • How good is the clock?

  • How optical atomic clock works Ramsey scheme

    2 π

    Measure: In

    iti al

    iz e

    wait

    0 1 2

    +

    0hν

    0E

    1E

    0

    1

    0

    2 π

    0 or 1 ?

    Atom should be now in if on resonance1

    0E

    1E 2E

    Quantum projection noise: can only get

    Repeat many times to get probability of excitation, scan different frequencies to maximize

    0 or 1

    detect fluorescence

  • How good is a clock: stability and uncertainty

    From: Poli et al. “Optical atomic clocks”, arXiv:1401.2378v2

    Stability is a measure of the precision with which we can measure a quantity. It is usually stated as a function of averaging time since for many noise processes the precision increases (i.e., the noise is reduced through averaging) with more measurements.

    Uncertainty: how well we understand the physical processes that can shift the measured frequency from its unperturbed (“bare"), natural atomic frequency.

  • How good is a clock: stability and uncertainty

    Stability as a function of averaging time

    Systematic evaluation of an atomic clock at 2×10-18 total uncertainty, T. L. Nicholson, S. L. Campbell, R. B. Hutson, G. E. Marti, B. J. Bloom, R. L. McNally, W. Zhang, M. D. Barrett, M. S. Safronova, G. F. Strouse, W. L. Tew, and J. Ye, Nature Commun. 6, 6896 (2015).

    Sr lattice clock

  • Clock instability Quantum projection noise limit

    The number of atoms or ions used in a single measurement

    N=1 for ions N>1000 for neutral atoms

    Duration of single measurement cycle

    The averaging period

    Clock transition frequency

    ( ) 0

    1 1 2y NT

    σ τ πν τ

    ≈ ( ) 15 15 10 /y s

    σ τ τ

    −= ×

    How long will it take to get to 10-19 uncertainty?

    Limited by clock state lifetime and laser stability

    79 years!

  • Clock instability Quantum projection noise limit

    The number of atoms or ions used in a single measurement

    N=1 for ions N>1000 for neutral atoms

    Duration of single measurement cycle

    The averaging period

    Clock transition frequency

    ( ) 0

    1 1 2y NT

    σ τ πν τ

    ≈ ( ) 15 11 10 /y s

    σ τ τ

    −= ×

    How long will it take to get to 10-19 uncertainty?

    Limited by clock state lifetime and laser stability

    3 years!

  • Clock instability Quantum projection noise limit

    The number of atoms or ions used in a single measurement

    N=1 for ions N>1000 for neutral atoms

    Duration of single measurement cycle

    The averaging period

    Clock transition frequency

    ( ) 0

    1 1 2y NT

    σ τ πν τ

    ≈ ( ) 16 11 10 /y s

    σ τ τ

    −= ×

    How long will it take to get to 10-19 uncertainty?

    Limited by clock state lifetime and laser stability

    11.6 days

    N=1 need T=10 seconds

    2 π

    2 π

    wait m ea

    su re

    in iti

    al ize

  • Theories with varying dimensionless fundamental constants String theories Other theories with extra dimensions Loop quantum gravity Dark energy theories: chameleon and quintessence models …many others

    Variation of fundamental constants

    J.-P. Uzan, Living Rev. Relativity 14, 2 (2011)

    Frequency of optical transitions depends on the fine-structure constant α.

    Measure the ratio of two optical clock frequencies to search for the variation of α.

    Dark matter can also cause variation of fundamental constants!

    A. Derevianko and M. Pospelov, Nature Phys. 10, 933 (2014), A. Arvanitaki et al., PRD 91, 015015 (2015)

  • Theories with varying dimensionless fundamental constants String theories Other theories with extra dimensions Loop quantum gravity Dark energy theories: chameleon and quintessence models …many others

    Variation of fundamental constants

    J.-P. Uzan, Living Rev. Relativity 14, 2 (2011)

    Frequency of optical transitions depends on the fine-structure constant α.

    Measure the ratio of two optical clock frequencies to search for the variation of α. Keep doing this for a while.

    Some clocks are more sensitive to this effect than others

  • Sensitivity of optical clocks to α-variation/dark matter

    0

    2K q E

    =

    2 2

    1 1

    1ln ( )Kv t v t

    K α α

    ∂ ∂ =