Single-arm gravitational wave detectors
based on atom interferometry
LISA Symposium X
Jason Hogan
May 22, 2014
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
Atom interference
Light
interferometer
Light fringes
Beamsplitter
Beamsplitter
Atom
interferometer
Atom fringes
Mirror
Atom
http://scienceblogs.com/principles/2013/10/22/quantum-erasure/
http://www.cobolt.se/interferometry.html
Measurement Concept
Essential Features
1. Atoms are good clocks
2. Light propagates across the baseline at a constant speed
Atom
Clock
Atom
Clock
L (1 + h sin(ωt ))
Simple Example: Two Atomic Clocks
Time
Phase 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 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., arXiv: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., arXiv:1206.0818, PRL (2013)
Reduced Noise Sensitivity
Leading order kinematic noise sources:
1. Platform acceleration noise da
2. Pulse timing jitter dT
3. Finite duration Dt of laser pulses
4. Laser frequency jitter dk
Differential phase shifts (kinematic noise) suppressed by Dv/c < 3×10-11
Satellite GW Antenna
Atoms
Common interferometer laser
Atoms
L ~ 100 - 1000 km
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
• Long duration
• Large wavepacket separation
4 cm
10 m Drop Tower Apparatus
Interference at long interrogation time
Wavepacket separation at
apex (this data 50 nK)
2T = 2.3 sec
Near full contrast
6.7×10-12 g/shot (inferred)
Interference (3 nK cloud)
Demonstrated statistical resolution:
~5 ×10-13 g in 1 hr (87Rb)
Dickerson, et al., PRL 111, 083001 (2013).
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 2T = 2.3 s
(unpublished)
Atom Lens
Geometric Optics:
position
Atom Lens:
time
Atom Lens Cooling
Optical Collimation:
position
Atom Cooling:
time
AC Stark Lens
Apply transient optical potential (“Lens beam”) to collimate atom cloud in 2D
“point source”
Radial Lens Beam
Time
2D Atom Refocusing
Lens
Without Lens
With Lens
Record
Temperature
VaryLow
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 (?)
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)
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
27
Sunnyvale, CA
Collaborators
Stanford
Mark Kasevich (PI)
Susannah Dickerson
Alex Sugarbaker
Tim Kovachy
Christine Donnelly
Chris Overstreet
Theory:
Peter Graham
Savas Dimopoulos
Surjeet Rajendran
Former members:
David Johnson
Sheng-wey Chiow
Visitors:
Philippe Bouyer (CNRS)
Jan Rudolph (Hannover)
NASA GSFC
Babak Saif
Bernard D. Seery
Lee Feinberg
Ritva Keski-Kuha
AOSense
Brent Young (CEO)