LIGO Document G1400886-v1
- Squeezed states of light have been successfully employed in interferometric gravitational-wave detectors to reduce quantum noise, thus becoming one of the most promising options for extending the astrophysical reach of the generation of detectors currently under construction worldwide. In these advanced detectors, quantum noise will limit sensitivity over the entire detection band. Therefore, to obtain the greatest benefit from squeezing, the injected squeezed state must be filtered using a long-storage-time optical resonator, or ``filter cavity'', so as to realise a frequency dependent rotation of the squeezed quadrature. Whilst the ultimate performance of a filter cavity is determined by its storage time, several practical decoherence and degradation mechanisms limit the experimentally achievable quantum noise reduction. We present the results of an analytical model which explores these mechanisms in detail. As an example, we apply our results to a 16 m filter cavity currently under consideration for the Advanced LIGO interferometers.
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