Aug 06, 2020

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

∂ ∂ =

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