Standard quantum limit / quantum noise

The next generation of interferometric terrestial gravitational wave detectors is expected to be limited by quantum noise and quantum back-action effects in the peak sensitivity frequency band. This limit to achievable sensitivity, called the standard quantum limit (SQL) is due by the quantum noise of the light in the interferometer. This is essentially the same situation as the Heisenberg microscope, where measurement of the position of a test mass by measuring the phase of light reflected from the mass causes perturbations of the masses momentum due to the radiation pressure of the incident photons. We have performed experiments to demonstrate classical noise cancellation via opto-mechanical coupling and are beginning preliminary SQL interferometer work. Once the SQL has been observed we aim to demonstrate techniques to supress the effects of quantum noise for improving the sensitivity of gravitational wave detectors.

The one-gram flexure used in SQL/QN experiments