1. Quantum Optics and Macroscopic Quantum Measurement
LIGO Laboratory, MIT

2. 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

3. 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

4. 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

5. 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

6. Radiation-pressure-induced Squeezing

7. 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

8. The Ponderomotive Interferometer

9. 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

10. Noise budget

11. 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