1. Quantum studies in LIGO Lab

2. The Quantum Limit in Advanced LIGO
Radiation pressure
Shot noise

3. Quantum activities in LIGO Lab
Injection of squeezed states
Demonstration on 40m prototype
Showed 2.9 dB (40%) improvement in SNR Goda et al., Nature Phys. 4, 472 (2008)
Proposed implementation on H1
Under consideration by review committee Sigg et al., LIGO-T C-D
Optical cooling and trapping of mirrors
All-optical trap for a 1 gram mirror
Minimum effective temperature of 0.8 K Corbitt et al., Phys. Rev. Lett. 98, (2007)
Optical dilution and cooling of a 1 gram mirror
Minimum effective temperature under 7 mK Corbitt et al., Phys. Rev. Lett. 99, (2007)
Active feedback cooling of the kilogram-scale LIGO mirrors
Minimum effective temperature of 1.4 mK LIGO Scientific Collaboration, in preparation
Shot noise
Radiation pressure noise

4. Quantum-enhanced interferometry
Squeezed state injection

5. Squeezing injection in 40m prototype
Laser
Prototype GW detector
SHG
Faraday isolator
The squeeze source drawn is an OPO squeezer, but it could be any other squeeze source, e.g. ponderomotive squeezer.
OPO
Homodyne Detector
Squeeze
Source
GW Signal

6. Quantum enhancement 2.9 dB or 1.4x
K. Goda, O. Miyakawa, E. E. Mikhailov, S. Saraf, R. Adhikari, K.McKenzie, R. Ward, S. Vass, A. J. Weinstein, and N. Mavalvala, Nature Physics 4, 472 (2008)

7. Proposed squeeze injection test in Enhanced LIGO circa 2010
Post-S6, pre-AdLIGO
Test performance of squeezer at ELIGO noise level
Improve SNR in shot-noise-limited band
Do no harm in other bands
Important step for readiness of squeezer for AdLIGO
Improve SNR and/or
Operate at lower power for same sensitivity

8. Mechanical oscillators in the quantum regime
Trapping and cooling mirrors

9. Reaching the quantum limit in mechanical oscillators
The goal is to measure non-classical effects with large objects like the (kilo)gram-scale mirrors
The main challenge  thermally driven mechanical fluctuations
Need to freeze out thermal fluctuations Zero-point fluctuations remain
One measure of quantumness is the thermal occupation number
Want N  1
Colder oscillator
Stiffer oscillator

10. Cooling using optical forces
Mechanical forces introduce thermal noise
Optical (or other ‘cold’) forces needed
Optical trapping and cooling
Radiation pressure of a detuned cavity provides restoring and damping forces
Restoring force  trap
Damping force  cool
Key ingredients
Light, movable mirrors
High laser power
Low noise performance to ensure mirror responds primarily to radiation pressure
Low noise readout of the mirror position

11. Experimental cavity setup
10%
90%
5 W
Optical fibers
1 gram mirror
Coil/magnet pairs
for actuation (x5)‏

12. An all-optical trap for a 1 gram mirror
Stiffer than diamond
Increasing subcarrier detuning
Stable Optical Spring
T. Corbitt, Y. Chen, E. Innerhofer, H. Müller-Ebhardt, D. Ottaway, H. Rehbein, D. Sigg, S. Whitcomb, C. Wipf and N. Mavalvala, Phys. Rev. Lett 98, (2007)

13. Cooling the kilogram scale mirrors of Initial LIGO
Teff = 1.4 mK N = 234 T0/Teff = 2 x 108
Mr ~ 2.7 kg ~ 1026 atoms
Wosc = 2 p x 0.7 Hz
LIGO Scientific Collaboration