Quantum studies in LIGO Lab

The Quantum Limit in Advanced LIGO Radiation pressure Shot noise

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-T070265-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, 150802 (2007) Optical dilution and cooling of a 1 gram mirror Minimum effective temperature under 7 mK Corbitt et al., Phys. Rev. Lett. 99, 160801 (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

Quantum-enhanced interferometry Squeezed state injection

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

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)

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

Mechanical oscillators in the quantum regime Trapping and cooling mirrors

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

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

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

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, 150802 (2007)

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