Gravitational wave detection using atom interferometry Frontiers of

Gravitational wave detection using atom interferometry Frontiers of New Physics: Colliders and Beyond Jason Hogan June 26, 2014

Gravitational Wave Detection frequency L (1 + h sin(ωt )) Megaparsecs… strain Why study gravitational waves? New carrier for astronomy Tests of gravity Cosmology

Laser Interferometer Detectors Gound-based detectors: LIGO, VIRGO, GEO (> 10 Hz) Space-based detector concept: LISA (1 m. Hz – 100 m. Hz)

Gravitational Wave Detection Why consider atoms? • Neutral atoms are excellent proof masses • Atom interferometry to measure geodesic • Atoms are excellent clocks

Atom interference Light interferometer Light fringes Beamsplitter Atom interferometer Atom fringes Mirror Atom http: //scienceblogs. com/principles/2013/10/22/quantum-erasure/ http: //www. cobolt. se/interferometry. html

Light Pulse Atom Interferometry • Long duration • Large wavepacket separation 4 cm

10 m Drop Tower Apparatus < 3 n. K

Interference at long interrogation time Wavepacket separation at apex (this data 50 n. K) 2 T = 2. 3 sec Near full contrast 6. 7× 10 -12 g/shot (inferred) Interference (3 n. K cloud) Demonstrated statistical resolution: ~5 × 10 -13 g in 1 hr (87 Rb) Dickerson, et al. , PRL 111, 083001 (2013).

Large momentum transfer atom optics Sequences of optical pulses can be used to realize large separations between interferometer arms. Example interferometer pulse sequence Chiow, PRL, 2011

Preliminary LMT in 10 m apparatus LMT using sequential Raman transitions with long interrogation time. 6 ħk 10 ħk 4 cm wavepacket separation 7 cm wavepacket separation LMT demonstration at 2 T = 2. 3 s (unpublished)

Single Baseline Gravitational Wave Detection frequency L (1 + h sin(ωt )) strain Are multiple baselines required? Motivation Laser interferometer GW detector • Formation flying: 2 vs. 3 spacecraft • Reduce complexity, potentially cost

Measurement Concept Essential Features 1. Atoms are good clocks 2. Light propagates across the baseline at a constant speed Atom Clock L (1 + h sin(ωt ))

Simple Example: Two Atomic Clocks Atom clock Phase evolved by atom after time T Time

Simple Example: Two Atomic Clocks GW changes light travel time Time Atom clock

Phase Noise from the Laser The phase of the laser is imprinted onto the atom. Laser phase noise, mechanical platform noise, etc. Laser phase is common to both atoms – rejected in a differential measurement.

Single Photon Accelerometer Three pulse accelerometer “Two level” atom Long-lived single photon transition (e. g. clock transition in Sr, Yb, Ca, Hg, etc. ) Graham, et al. , PRD 78, 042003, (2008). Yu, et al. , GRG 43, 1943, (2011).

Two-photon vs. single photon configurations 1 photon transitions 2 photon transitions Sr Rb How to incorporate LMT enhancement? Graham, et al. , PRD 78, 042003, (2008). Yu, et al. , GRG 43, 1943, (2011).

Laser frequency noise insensitive detector Pulses from alternating sides allow for sensitivity enhancement (LMT atom optics) Excited state Laser noise is common Graham, et al. , ar. Xiv: 1206. 0818, PRL (2013)

LMT enhancement with single photon transition Example LMT beamsplitter (N = 3) Each pair of pulses measures the light travel time across the baseline. Excited state Graham, et al. , ar. Xiv: 1206. 0818, PRL (2013)

Reduced Noise Sensitivity Leading order kinematic noise sources: 1. Platform acceleration noise da 2. Pulse timing jitter d. T 3. Finite duration Dt of laser pulses 4. Laser frequency jitter dk Differential phase shifts (kinematic noise) suppressed Dv/c by< 3× 10 -11

Satellite GW Antenna Atoms Common interferometer laser L ~ 100 - 1000 km Atoms

Potential Strain Sensitivity Possible sensitivity on ground JH, et al. , GRG 43, 7 (2011).

Stochastic GW Sensitivity AGIS Requires correlation among multiple independent baselines

Technology development for GW detectors 1) Large wavepacket separation (meter scale) 2) Laser frequency noise mitigation strategies 3) Ultra-cold atom temperatures (picokelvin) 4) Long interferometer time (>10 seconds) 5) Spatial wavefront of laser

Atom Lens Cooling Optical Collimation: position Atom Cooling: time

Lens 2 D Atom Refocusing Transverse dipole potential approximately harmonic Laser beam profile Without Lens With Lens

Vary Focal Length North West

Extended free-fall on Earth Lens Launch Lens Relaunch Detect Launched to 9. 375 meters Relaunched to 6 meters Image of cloud after 5 seconds total free-fall time Towards T > 10 s interferometry (? )

Sr compact optical clock 6 liter physics package As built view with front panel removed in order to view interior. AOSense 408 -735 -9500 AOSense. com 29 Sunnyvale, CA

Future GW work Single photon AI gradiometer proof of concept Ground based detector prototype work 10 m tower studies MIGA; ~1 km baseline (Bouyer, France)

Collaborators Stanford Mark Kasevich (PI) Susannah Dickerson Alex Sugarbaker Tim Kovachy Christine Donnelly Chris Overstreet Theory: Savas Dimopoulos Peter Graham Surjeet Rajendran Former members: Sheng-wey Chiow David Johnson Visitors: Philippe Bouyer (CNRS) Jan Rudolph (Hannover) NASA GSFC Babak Saif Bernard D. Seery Lee Feinberg Ritva Keski-Kuha AOSense Brent Young (CEO)

Phase shear readout Phase Shear Readout (PSR) F=2 (pushed) F=1 g F=2 (pushed) 1 cm ≈ 4 mm/s Mitigates noise sources: ü Pointing jitter and residual rotation readout ü Laser wavefront aberration in situ characterization Single-shot interferometer phase measurement

Phase shear readout Phase Shear Readout (PSR) F=2 (pushed) F=1 g F=2 (pushed) 1 cm ≈ 4 mm/s Mitigates noise sources: ü Pointing jitter and residual rotation readout ü Laser wavefront aberration in situ characterization Single-shot interferometer phase measurement

Phase shear readout Phase Shear Readout (PSR) F=2 (pushed) F=1 g F=2 (pushed) 1 cm ≈ 4 mm/s Mitigates noise sources: ü Pointing jitter and residual rotation readout ü Laser wavefront aberration in situ characterization Single-shot interferometer phase measurement

Phase shear readout Phase Shear Readout (PSR) F=2 (pushed) F=1 g F=2 (pushed) 1 cm ≈ 4 mm/s Mitigates noise sources: ü Pointing jitter and residual rotation readout ü Laser wavefront aberration in situ characterization Single-shot interferometer phase measurement