Optomechanics Experiments Radiation Pressure Rules MIT Quantum Measurement Group

Quantum optomechanics Techniques for improving gravitational wave detector sensitivity Tools for quantum information science Opportunities to study quantum effects in macroscopic systems Observation of quantum radiation pressure Generation of squeezed states of light Entanglement of mirror and light quantum states Quantum states of mirrors

Optomechanical coupling The radiation pressure force couples the optical field to mirror motion Alters the dynamics of the mirror Spring-like forces  optical trapping Viscous forces  optical damping Tune the frequency response of the GW detector Manipulate the quantum noise Quantum radiation pressure noise and the standard quantum limit Produce quantum states of the mirrors and light Classical Tuning frequency response is used to manipulating the signal. Improved sensitivity at optical spring resonant frequency. Squeezing manipulates the noise Quantum

Optomechanical coupling: Radiation pressure forces Detune optical field from cavity resonance Change in mirror position changes intracavity power  radiation pressure exerts force on mirror Time delay in cavity results in cavity response doing work on mechanics

Gram-scale mirrors

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

Trapping and cooling Stable optical trap with bichromatic light Dynamic backaction cooling Stiff! Stable! T. Corbitt et al., Phys. Rev. Lett 98, 150802 (2007)

The experiment grows Squeezed Vacuum fluctuations T. Corbitt et al., Phys. Rev. A 73, 023801 (2006) Two identical cavities with 1 gram mirrors at the ends Common-mode rejection cancels out laser noise

The experiment grows

Optically trapped and cooled mirror Optical fibers Teff = 0.8 mK N = 35000 Mechanical Q = 20000 Cooling factor larger than mechanical Q because Gamma = Omega_eff/Q. The OS increases Omega but doesn’t affect Gamma (OS is non-mechanical), so Q must increase to keep Gamma constant. 1 gram mirror C. Wipf, T. Bodiya, et al. (March 2010)

That elusive quantum regime Thermal noise Radiation pressure noise goal (5 W input) C. Wipf, T. Bodiya, et al. (Feb. 2011)

Ponderomotive Squeezing 7 dB or 2.25x Squeezing T. Corbitt, Y. Chen, F. Khalili, D.Ottaway, S.Vyatchanin, S. Whitcomb, and N. Mavalvala, Phys. Rev A 73, 023801 (2006)

Cryogenic microgram-scale mirrors Thomas Corbitt @ MIT (but soon LSU)

Micromirror oscillators AlGaAs layers forming a Bragg mirror ~ 1 to 5 mm long, ~10 μm supports, 50 to 100 μm mirror pads Fundamental frequency ~ 200 Hz Q factor ~ 2x105 at 5 K Mass ~ 250 nanograms Reflectivity ~ 99.982% Very fragile Power handling: breaks at >100 mW of incident power Fabricated by Garrett Cole at Univ. of Vienna

Experimental layout

Noise budget

What can we learn? Verify models of radiation pressure noise, squeezed radiation pressure noise, sub-SQL topologies Verify models of thermal noise (ability to measure thermal noise as function of both frequency and temperature across broad bandwidth in monolithic structure) Characterize materials and understand dissipation mechanisms Gain experience in low vibration cryogenics

Amazing cast of characters MIT Thomas Corbitt Christopher Wipf Timothy Bodiya Sheila Dwyer Lisa Barsotti Nicolas Smith-Lefevbre Eric Oelker Rich Mittleman MIT LIGO Laboratory Collaborators Yanbei Chen & group David McClelland & group Roman Schnabel & group Stan Whitcomb Daniel Sigg Caltech 40m Lab team Caltech LIGO Lab Garrett Cole of Aspelmeyer group (Vienna) LIGO Scientific Collaboration