Probing Fundamental Physics with Long-Baseline Atom Interferometry - PowerPoint Presentation

1. Probing Fundamental Physics with Long-Baseline Atom InterferometryTim KovachyDepartment of Physics and Astronomy and Center for Fundamental Physics (CFP), Northwestern UniversityCPAD 2021

2. Brief overview of atom interferometryEnabling technology advances for large-area/long-baseline atom interferometry demonstrated with 10-meter baselinesQuantum coherence over tens of centimeters and multiple secondsScience motivation for extending to longer baselinesSearch for wavelike, ultralight dark matter (DM)Gravitational wave (GW) detection in new frequency rangesFoundational quantum scienceMAGIS-100 100-meter baseline atom interferometer at FermilabConceptual overview, how is it sensitive do DM and GW signals?Summary of the experimentPathfinder for even longer baseline future detectorsQuantum technology development path, with MAGIS-100 as a testbedSummary

3. Laser pulses act as beam splitters and mirrors for atomic wavefunction (n photon momentum kicks)Highly sensitive to accelerations (or to time-variations of atomic energy levels)gAtom InterferometryFor n=100, 461 nm light (for Sr atoms), T = 1 s, phase shift from g is 1010 radiansnAcceleration sensitivity (consideration sensitivity to g as illustrative example)

4. Long duration (2 seconds), large separation (tens of centimeters) matter wave interferometerSensitive enough that Earth’s gravity gradient creates a 1 radian phase shift over the millimeter size of the atom cloud Up to 90 photons worth of momentum: large momentum transfer (LMT)max wavepacket separationMacroscopic Scale Atom InterferometryTK, P. Asenbaum, C. Overstreet, C. Donnelly, S. Dickerson, A. Sugarbaker, J. Hogan, and M. Kasevich, Nature 2015P. Asenbaum, C. Overstreet, TK, D. Brown, J. Hogan, and M. Kasevich, PRL 2017

5. Gradiometer interference fringes10 ћk30 ћkDifferential measurement between two interferometers separated over a baseline Used macroscopic scale atom interferometers for enhanced sensitivity, observed common mode suppression of laser noiseSee also McGuirk et al., PRA 65, 033608 (2002)Precision Gravity GradiometryP. Asenbaum, C. Overstreet, TK, D. Brown, J. Hogan, and M. Kasevich, PRL 2017

6. Phase shift from spacetime curvatureSpacetime curvature across a single particle's wavefunctionGeneral relativity: gravity (coordinate invariant) = curvature (tidal forces)Curvature-induced phase shifts have been described as first true manifestation of gravitation in a quantum system (wavefunction no longer exists in single local inertial frame, experiences gravity nonlocally)Local source mass induces tidal force across macroscopic wavefunction, measured associated phase shiftPlaces bounds on certain gravitational decoherence models (N. Altimirano et al., Classical and Quantum Gravity, 2018)

7. ~1e6 Rb atoms/shotAtom clouds with effective temperatures as low as 50 pK10 meter Atomic Fountain

8. Atom interferometry well-suited to the lightest part of this mass range (general axion- and hidden-photon-like particles)DM signatures include time-dependent atomic energy levels and time-dependent EP-violating accelerations (use dual isotope interferometer for latter case)Technologies to Cover Range of Wave DM MassesFrom Rocky Kolb presentation at HEPAP.ARIADNE

9. Long free fall times enabled by long-baseline atom interferometry offer potential to extend quantum coherence to distance scales of several meters for many secondsMAGIS-100 may ultimately be able to extend this to tens of meters with further development of advanced atom optics techniquesCan probe validity of quantum mechanics in an unprecedented macroscopic regime, testing a variety of proposed fundamental decoherence mechanisms (some related to gravity)Foundational Quantum ScienceArndt and Hornberger, Nature Physics 2014Bassi et al., RMP 2013Nimmrichter and Hornberger, PRL 2013Altimirano et al., Classical and Quantum Gravity, 2018Bassi et al., Classical and Quantum Gravity, 2017

10. Megaparsecs…Gravitational waves science:New carrier for astronomy: Generated by moving mass instead of electric chargeProbing the early universe: Can see to the earliest times in the universe, study corresponding high energy scalesTests of gravity: Extreme systems (e.g., black hole binaries) test general relativity L (1 + h sin(ωt ))strainfrequencyGravitational Wave Detection

11. Laser Interferometer DetectorsGound-based detectors: e.g.: LIGO, VIRGO, GEO, proposed ET (> ~10 Hz)Space-based detector concept: planned LISA mission (1 mHz – 100 mHz), also proposals to extend LISA concept to higher frequencies (e.g., DECIGO)

12. Gravitational wave frequency bandsMid-bandThere is a gap between the LIGO and LISA detectors (~ 0.1 Hz – 10 Hz).Moore et al., CQG 32, 015014 (2014)

13. Mid-band ScienceMid-band discovery potential-Historically every new band/modality has led to discovery-Observe LIGO sources when they are youngerCosmological signals that give insight into high energy physics-GWs from inflation and reheating-Thermal phase transitions in the early universe at scales above the weak scale-Quantum tunnelling transitions in cold hidden sectors-Networks of cosmic strings-Collapsing domain walls-Axion signals from the early universe-operating in mid-band instead of lower frequencies advantageous for avoiding white dwarf confusion noiseOptimal for sky localization Predict when and where events will occur (before they reach LIGO band)Observe run-up to coalescence using electromagnetic telescopesAstrophysical SourcesWhite dwarf binaries (Type IA supernovae), black hole binaries, intermediate mass black holes, and neutron star binaries

14. MAGIS-100 detector at Fermilab - Based on key technology demonstrated at the 10 meter scale - 100 meter access shaft – 100 meter atom interferometer - Search for dark matter coupling in the Hz range - Intermediate step to full-scale detector for mid-band GW (0.3-3 Hz)Source 1Source 250 meters50 meters100 metersSource 3Matter wave Atomic Gradiometer Interferometric SensorAbe et al., submitted 2021

15. Ultimate Vision: Global Network of Long-Baseline Atomic DetectorsConstruction of MIGA detector in France underway (group of P. Bouyer, Canuel et al., Scientific Reports 8, 2018)AION: MAGIS-like detector in UK (Badurina et al., J. of Cosmology and Astrophysics, 2020)ZAIGA in China (Zhan et al., International Journal of Modern Physics D, 2020)Others (e.g., Naval Postgraduate School, Rasel group in Hannover)?Optical lattice atomic clocks in space (Kolkowitz et al., PRD, 2016)

16. Measurement ConceptEssential FeaturesLight propagates across the baseline at a constant speedAtoms are good clocks and good inertial proof masses (freely falling in vacuum, not mechanically connected to Earth). Clocks read transit time signal over baselineGW changes number of clock ticks associated with transit by modifying light travel time across baseline, DM changes number of clock ticks by modulating clock frequency ( i.e., atomic transition frequency)Many pulses sent across baseline (large momentum transfer) to coherently enhance signalAtomClockAtomClockL (1 + h sin(ωt ))Yu and Tinto, GRG 2011; Graham et al., PRL 2013; Arvanitaki et al., PRD 2018

17. Strontium clock transitionSr has a narrow optical clock transition with a long-lived excited state (natural lifetime >100 s)Can have long lived superpositions of ground + excited state with a large energy difference, useful for very precise timing measurementsFor freely falling atoms, must account for photon momentum recoil when transition between clock states, two branches of wavefunction separate spatially—hybrid clock/atom interferometerUse clock transition for atom interferometry (demonstration on 698 nm transition: Hu et al., PRL 2017; LMT clock atom interferometry on 689 nm transition: Rudolph et al, PRL 2020)

18. MAGIS-100 Experiment17 modules, each with magnetic shielding, vacuum pipe, current-carrying wires for generating bias magnetic fieldThree Sr atom sources over 100 m baseline, local optical lattices can launch atoms from each sourceHigh-power laser system with agile frequency control, spatially filtered beam mode, and precisely controlled pointing Construction and testing of subsystems underwayAbe et al., submitted 2021

19. MAGIS-100 Dark Matter SearchesExample: coupling to electron mass or fine structure constantBound assumptions: 50 m launch, 1000 ħk atom optics, 108 atoms/s flux, shot noise limited, 1 year of dataExample: vector DM coupling to B-LBound assumptions: 50 m launch, 100 ħk atom optics, 106 atoms/s flux, shot noise limited, 1 year of data (solid curve); 100 m launch, 1000 ħk atom optics, 108 atoms/s flux, shot noise limited, 1 year of data (dashed curve);

20. -Path to continued improvement through quantum sensing R&D efforts, which we are pursuing (MAGIS-100 serving as quantum testbed)-Potential for future km-scale terrestrial detector and satellite-based detector-GGN (gravity gradient noise) important at lower frequencies for terrestrial detectors: seismic waves disturb local mass distribution, cause oscillating gravity gradient that is a noise background Mid-band Gravitational Wave Detection

21. Larger momentum transfer atom optics (goal: ~104 photons) for larger wavefunction delocalizationExploit substantially reduced spontaneous emission rate for single photon atom optics on Sr clock transitionHigh-fidelity pulses using optimal quantum control protocolsMore laser power enables more efficient transferDevelopment of higher power laser system based on coherent combination of multiple lasersStrategies to distinguish GGN from GW signal by using a string of many interferometers: GGN expected to have more rapidly varying spatial dependence (see, e.g., Canuel et al., Scientific Reports 8, 2018)Improved phase resolutionHigher atom fluxSpin squeezing for Sr atoms (make use of entanglement)R&D Directions

22. Long-baseline atom interferometry promising for dark matter searches, gravitational wave detection, and foundational quantum scienceMAGIS-100 will serve as pathfinder experiment and testbed for advanced quantum sensing technologiesActive efforts to develop a global network of long-baseline atomic detectors, potential for future detectors in space Conclusion

23. AcknowledgementsMAGIS CollaboratorsJason Hogan (Spokesperson) (Stanford)Mark Kasevich (Stanford) Peter Graham (Stanford)Rob Plunkett (FNAL)Steve Geer (FNAL)Roni Harnik (FNAL)Swapan Chattopadhyay (FNAL & NIU)Surjeet Rajendran (Johns Hopkins)Jonathon Coleman (Liverpool)Jeremiah Mitchell (Cambridge)Val Gibson (Cambridge)John March-Russell (Oxford)Ian Shipsey (Oxford)Chris Foot (Oxford)Ariel Schwartzman (SLAC) Northwestern TeamTejas Deshpande (postdoc)Natasha Sachdeva (postdoc)Ken DeRose (PhD student)Jonah Glick (PhD student)Yiping Wang (PhD student)

24. Two ways to get a signal:Gravitational waveDark matterPhase shift of an interferometer determined by difference in times spent in excited clock state for arm 1 vs arm 2Look at difference in phase shifts for two interferometers separated by baseline ~L (gradiometer phase shift)Magnitude of contribution to gradiometer phase shift from each interferometer zone:For constant (or linearly drifting) L and transition frequency, gradiometer phase shift cancels between all three zonesTo have a nonzero gradiometer phase shift, need transition frequency or L to vary on the time scale of time T between each zoneGraham et al., PRL 110, 171102 (2013).Arvanitaki et al., PRD 97, 075020 (2018).Gradiometer Signalbeam splitter 1 beam splitter 2 mirror