Quantum Optics and Macroscopic Quantum Measurement LIGO Laboratory, MIT

What we are about Precision interferometry (for gravitational wave detection) beyond the quantum limit Manipulating macroscopic objects such as the mirrors of the interferometer using the quantum properties of light Measuring quantum state of macroscopic objects

The LIGO group at MIT is ~25 people Who we are... The LIGO group at MIT is ~25 people 5 faculty and senior research scientists ~10 scientists, post-docs and engineering staff ~10 graduate students The Quantum Measurement group Corbitt, Goda, Wipf, Pelc, Zaheer Innerhofer, Mikhailov Nergis Lab visit/tour Friday 10am in NW17

The ‘Standard Quantum Limit’ How precisely can we measure the position of a particle using light? Quantum fluctuations on the light (shot noise) Use N photons in the measurement Get sqrt(N) uncertainty Back action (radiation pressure noise) Photon impart momentum to the particle Fluctuations in photon number gives uncertainty in position of the particle

Some (sub-)quantum states of light Analogous to the phasor diagram Stick  dc term Ball  fluctuations Common states Coherent state Vacuum state Amplitude squeezed state Phase squeezed state McKenzie

Radiation-pressure-induced Squeezing

The principle A “tabletop” interferometer that generates squeezed light Use radiation pressure as the squeezing mechanism Intensity fluctuations of the light push on the mirror Mirror motion imprinted on phase of the light Amplitude and phase correlations  squeezing Relies on intrinsic quantum physics of optical field-mechanical oscillator correlations Quantum radiation pressure  squeezing  sub-SQL

The Ponderomotive Interferometer

High circulating laser power High-finesse cavities Key ingredients High circulating laser power 10 kW High-finesse cavities 15000 Light, low-noise mechanical oscillator mirror 1 gm with 1 Hz resonant frequency Optical spring Detuned arm cavities

Noise budget

Why is this interesting/important? First ever (?) demonstration of radiation-pressure induced squeezing Probes quantum mechanics of optical field-mechanical oscillator coupling at 1 g mass scales Test of low noise optical spring Suppression of thermal noise Simulations and techniques useful for precision interferometry (e.g. GW interferometers) Quantum optical simulation package Michelson detuning Role of feedback control in these quantum systems Quantum decoherence tests