Jason Hogan

May 22, 2014

LISA Symposium X

Single-arm gravitational wave detectors based on atom interferometry

Are multiple baselines required?

L (1 + h sin(ωt ))

strain

frequency

Single Baseline Gravitational Wave Detection

Motivation• Formation flying: 2 vs. 3 spacecraft• Reduce complexity, potentially costLaser

interferometer GW detector

Atom interference

Light interferometer

Atom interferometer

Atom

http://scienceblogs.com/principles/2013/10/22/quantum-erasure/http://www.cobolt.se/interferometry.html

Light fringes

Beamsplitter

Beamsplitter

Mirror

Atom fringes

Measurement Concept

Essential Features

1. Atoms are good clocks2. Light propagates across the baseline at a constant speed

AtomClock

AtomClock

L (1 + h sin(ωt ))

Simple Example: Two Atomic Clocks

TimePhase evolved by atom after time T

Simple Example: Two Atomic Clocks

Time GW changes light travel time

Phase difference

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

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 configurations2 photon transitions 1 photon transitions

Rb Sr

How to incorporate LMT enhancement?

Graham, et al., PRD 78, 042003, (2008).Yu, et al., GRG 43, 1943, (2011).

Laser frequency noise insensitive detector

Graham, et al., arXiv:1206.0818, PRL (2013)

Laser noise is common

Excitedstate

Pulses from alternating sides allow for sensitivity enhancement (LMT atom optics)

LMT enhancement with single photon transition

Graham, et al., arXiv:1206.0818, PRL (2013)

Example LMT beamsplitter (N = 3)

Each pair of pulses measures the light travel time across the baseline.

Excitedstate

Reduced Noise Sensitivity

Differential phase shifts (kinematic noise) suppressed by Dv/c < 3×10-11

1. Platform acceleration noise da2. Pulse timing jitter dT3. Finite duration Dt of laser pulses4. Laser frequency jitter dk

Leading order kinematic noise sources:

Satellite GW Antenna

Common interferometer laser

L ~ 100 - 1000 km

Atoms Atoms

JMAPS bus/ESPA deployed

Potential Strain Sensitivity

J. Hogan, et al., GRG 43, 7 (2011).

Technology development for GW detectors

1) Laser frequency noise mitigation strategies

2) Large wavepacket separation (meter scale)

3) Ultra-cold atom temperatures (picokelvin)

4) Very long time interferometry (> 10 seconds)

Ground-based GW technology development

4 cm• Long duration• Large wavepacket separation

10 m Drop Tower Apparatus

Interference at long interrogation time

2T = 2.3 secNear full contrast6.7×10-12 g/shot (inferred)

Interference (3 nK cloud)

Wavepacket separation at apex (this data 50 nK)

Dickerson, et al., PRL 111, 083001 (2013).

Demonstrated statistical resolution: ~5 ×10-13 g in 1 hr (87Rb)

Preliminary LMT in 10 m apparatus

7 cm wavepacket separation10 ħk

4 cm wavepacket separation6 ħk

LMT using sequential Raman transitions with long interrogation time.

LMT demonstration at 2T = 2.3 s (unpublished)

Atom Lens

position

time

Geometric Optics:

Atom Lens:

Atom Lens Cooling

Optical Collimation:

Atom Cooling:

position

time

Radial Lens Beam“point source”

AC Stark LensApply transient optical potential (“Lens beam”) to collimate atom cloud in 2D

Time

2D Atom Refocusing

Without Lens

With Lens

Lens

Record Low Temperature

North

West

Vary Focal Length

Extended free-fall on Earth

Lens

Launch Lens Relaunch Detect

Launched to 9.375 metersRelaunched to 6 meters

Image of cloud after 5 seconds total free-fall

time

Towards T > 10 s interferometry (?)

Future GW workSingle photon AI gradiometer proof of concept

Ground based detector prototype work

MIGA; ~1 km baseline (Bouyer, France)

10 m tower studies

27AOSense 408-735-9500AOSense.comSunnyvale, CA

6 liter physics package

As built view with front panel removed in order to view interior.

Sr compact optical clock

CollaboratorsNASA GSFC

Babak SaifBernard D. Seery Lee FeinbergRitva Keski-Kuha

Stanford Mark Kasevich (PI)Susannah DickersonAlex SugarbakerTim KovachyChristine DonnellyChris Overstreet

Theory:Peter GrahamSavas DimopoulosSurjeet Rajendran

Former members:David Johnson Sheng-wey Chiow

Visitors:Philippe Bouyer (CNRS)Jan Rudolph (Hannover)

AOSenseBrent Young (CEO)