Cavity-enhanced sources of non-classical light (“squeezed light”) yield a reduced quantum noise floor not only at low measurement frequencies, but at every free spectral range of the optical resonator.
This high-frequency squeezing is – by design and in contrast to the baseband squeezing already employed in GEO600 – not masked by technical noise. It can therefore directly be used in precision spectroscopy / metrology applications, i.e. with less preparatory stabilisation effort.
We are working on a high-sensitivity phase-measurement of a Fabry-Pérot cavity with an increased signal-to-noise ratio making use of the reduced shot noise level given by high-frequency squeezing. The theoretical underpinnings for this experiment were laid by E. Huntington (UNSW@ADFA, Canberra, Australia) with whom our group upholds a very active research collaboration.
In addition to direct metrological applications for high-frequency squeezed light, a squeezing comb could potentially be exceedingly useful for quantum information as a resource for information multiplexing.