New physics searches with atomic clocks

MARIANNA SAFRONOVA

Next Frontiers in the Search for Dark Matter GGI, Florence, Italy GPS satellites: microwave atomic clocks

airandspace.si.edu

Atomic clocks will not lose one second in 30 billion years What dark matter affects atomic energy levels?

n 0 is a clock frequency

What dark matter can you detect if you can measure changes in atomic frequencies to 20 digits? What dark matter can you detect if you can measure changes in atomic frequencies to 20 digits?

What if you can get extra 5 orders of DM sensitivity by using a nuclear transition?

What new dark matter detection opportunity we get with a network of clocks? Clocks: new dark matter detectors

• 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

Nicholson et al., Nature Comm. 6, 6896 (2015) Sr: 2×10-18 http://www.nist.gov/pml/div689/20140122_strontium.cfm Overview

• How atomic clocks work? • Ultralight dark matter & variation of fundamental constants • Present dark matter searches with clocks • The clocks of the next decade • Testing Lorentz invariance with clocks Ingredients for a clock

1. Need a system with periodic behavior: it cycles occur at constant frequency

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

NOAA/Thomas G. Andrews 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) 171Yb+ 3. Build a laser in resonance with this ION atomic frequency

4. Count cycles of this signal

Ludlow et al., RMP 87, 637 (2015) Extraordinary progress in the control of 300K atomic systems

3D

pK Image: Ye group and Steven Burrows, JILA Ultracold Trapped Precisely controlled 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.

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

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

10-22 eV 10-12 eV µeV eV GeV

Ultralight dark matter has to be bosonic – Fermi velocity for DM with mass >10 eV is higher than our Galaxy escape velocity.

Bosonic dark matter (DM) with mass mf < 1eV -3 Dark matter density in our Galaxy > l dB where ldB is the de Broglie wavelength of the particle. Then, the dark matter exhibits coherence and behaves like a classical field.

Picture credit: Andrew Long’s 2018 LDW talk Effects of ultralight DM on standard model particles Such DM field can:

ü Cause precession of nuclear and electron spins

ü Drive currents in electromagnetic systems

ü Induce equivalence principle-violating accelerations of matter

ü Modulate the values of the fundamental constants, inducing changes in atomic transition frequencies and local gravitational field

Search for new physics with atoms and molecules, M. S. Safronova, D. Budker, D. DeMille, Derek F. Jackson-Kimball, A. Derevianko, and Charles W. Clark, Rev. Mod. Phys. 90, 025008 (2018). Long history of astrophysics searches for the variation of fine-structure constant a from quasar absorption spectra

Scientific American: A Matter of Time 23, 60 (2014) Hint of non-zero result Spatial variation of a 4s effect controversial

http://physicsworld.com/cws/article/news/2015/feb/24/quasar- spectrum-shines-a-new-light-on-unchanged-fundamental-constants Variation of fundamental constants

Theories with varying dimensionless fundamental constants J.-P. Uzan, Living Rev. Relativity 14, 2 (2011) String theories 2 Other theories with extra dimensions 1 e a = Loop quantum gravity 4pe !c Dark energy theories: chameleon and quintessence models 0 ……Various light scalars

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

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

Scientific American 314, 38 (2016) How to detect ultralight dark matter with clocks?

Asimina Arvanitaki, Junwu Huang, and Ken Van Tilburg, PRD 91, 015015 (2015)

10-22 eV 10-12 eV µeV eV GeV

Dark matter field couples to electromagnetic interaction and “normal matter”

It will make fundamental coupling constants and mass ratios oscillate

Atomic energy levels will oscillate so clock frequencies will oscillate

Can be detected with monitoring ratios of clock frequencies over time. Ultralight scalar dark matter

Dark matter dilaton coupling to the Standard Model

photons gluons Dark matter

quarks electrons

Measure: couplings di vs. DM mass

A. Arvanitaki et al., PRD 91, 015015 (2015) Sensitivity of optical clocks to a-variation and dark matter/new physics Enhancement factor æöa 2 EE=+q -1 2q 0 ç÷2 K = a0 èø E0 Need: large K for at least one for the clocks

Best case: large K2 and K1 of opposite sign for clocks 1 and 2

¶¶v2 1 a ln = ()K2 - K1 ¶¶tv1 a t Test of a-variation Frequency ratio accuracy 10-18 100 10-20 Easier to measure large effects! Observable: ratio of two clock frequencies Measure a ratio of Al+ n (Hg + ) KHg()+ =-2.9 clock frequency to Hg+ + K Al + = 0.01 Not sensitive to DM, clock frequency n (Al ) ( ) used as reference

1126 nm 1070 nm laser fiber laser

×2 ×2

fiber

×2 ×2 9Be+ 199Hg++ fb,Al Hg fb,Hg 27Al+

n frep+ fceo m frep+ fceo Picture credit: Jim Bergquist Science 319, 1808 (2008) Clock measurement protocols for the dark matter detection

Single clock ratio measurement: averaging over time t1 Make N such measurements, preferably regularly spaced

tint

Dt

Detection signal: A peak with monochromatic frequency in the discrete Fourier transform of this time series. A. Arvanitaki et al., PRD 91, 015015 (2015) Clock measurement protocols for the dark matter detection

Single clock ratio measurement: averaging over time t1 Make N such measurements, preferably regularly spaced

Al least one dark matter oscillation during this time

tint

Dt No more than one dark matter oscillation during this time or use extra pulse sequence Detection signal: A peak with monochromatic frequency in the discrete Fourier transform of this time series. A. Arvanitaki et al., PRD 91, 015015 (2015) Ultralight dark matter

DM virial velocities ~ 300 km/s Dark matter parameters

One oscillation per second

One oscillation per 11 days Coupling of dark matter to photons to matter dark of Coupling

From PRL 120, 141101 (2018) Slide credit: Gilad Perez Slide credit: Gilad Perez Transient variations

Dark matter clumps: point-like monopoles, one-dimensional strings or two-dimensional sheets (domain walls).

If they are large (size of the Earth) and frequent enough they may be detected by measuring changes in the synchronicity of a global network of atomic clocks.

GPM.DM collaboration: Roberts at el., Nature Communications 8, 1195 (2017) Fiber-linked optical atomic clocks new limit: arXiv:1907.02661 The next decade of atomic clocks

Ion chains Large ion crystals Clocks with ultracold Science 347, highly charged ions 1233 (2015)

Measurements beyond the quantum limit Entangled clocks Orders of magnitude improvements with current clocks and new clocks Image credits: NIST, Innsbruck group, MIT Vuletic group, Ye JILA group 8.28±0.17 eV Nuclear clock

Only energy of a nuclear transition that is laser-accessible !

Existence of this isomer 229mTh state was confirmed: Wense et al., Nature 533, 4751 (2016)

Laser spectroscopic characterization of the 229mTh nuclear clock isomer 229mTh (measured isomer nuclear radius and quadrupole Nuclear transition moment): Thielking et al., Nature 556, 321(2018) 150(3) nm Science 347, 1233 (2015) Lifetime ~ 5000s New transition energy measurement: 8.28 ± 0.17 eV 229Th B. Seiferle et al., Nature 573, 243 (2019) Th nuclear clock 229mTh

Large (MeV) Coulomb energy difference Nuclear transition compensated by MeV difference in the 150(3) nm nuclear binding energy? Lifetime ~ 5000s

229Th

Then, possible 4-5 orders of magnitude enhancement to

mq the variation of a and but orders of magnitude LQCD uncertainty in the enhancement factors. Provides access to couplings of Standard Model particles to

dark matter via other terms besides the de (E&M). It is crucial to establish actual enhancement! Search for physics beyond the Standard Model with atomic clocks

Image credit: Jun Ye’s group Dark matter searches Tests of the Search for the violation equivalence of Lorentz invariance principle

Image credit: NASA Are fundamental a constants constant? Gravitational wave detection with atomic clocks PRD 94, 124043 (2016) Measure frequency difference of two Yb+ clocks to probe Lorentz violation Dnnn=12- Two orders of magnitude improvement

C. Sanner, N. Huntemann, R. Lange, C. Tamm, E. Peik, M. S. Safronova, S. G. Porsev, Nature 567, 204 (2019). Advances in Precision Atomic physics tools • Atomic clocks • Atom and Light interferometers Matter Waves! • Atomic magnetometers

• Ultracold and trapped atoms and ions • Cold molecular beams • Quantum information technologies

• New: Cooling of highly-charged ions • New: UV frequency combs • In progress: laser cooling of molecules

Need new ideas!

More DM candidates? What are the best motivated scalar candidates? Detection goals … naturalness line? How to motivate/produce topological defects? How to detect various other transient DM “clumps” with clock networks? How to use clocks for measure “heavier” ultralight DM?

New ideas for DM searches with other AMO technologies?