Speaker
Description
Gravitational-wave detectors rely on frequency-dependent quantum squeezing to minimize quantum noise across the entire detection bandwidth. While current detectors achieve this with a single filter cavity (FC), future instruments like the Einstein Telescope Low-Frequency (ETLF) will operate with a detuned signal recycling cavity, requiring a complex rotation of the squeezing ellipse for optimal noise reduction, which cannot be addressed by a single filter cavity. Instead, two filter cavities (2FC) or a three-mirror coupled filter cavity (CFC) must be implemented. The Quantum Fresco project, developed at the laboratory Astroparticule et Cosmologie (APC), aims to determine the best configuration for frequency-dependent squeezing in detuned detectors, with a focus on the Einstein Telescope. Our work combines theoretical modeling and experimental validation. We derived first the model describing quantum degradation in multi-cavity systems, enabling a comparative analysis of the 2FC and CFC setups in terms of feasibility and performance, while accounting for key degradation sources such as optical losses, mode mismatch, and phase noise (Phys. Rev. D 112, 122001). We are now moving to a table-top experimental demonstration of the complex rotation of the squeezing ellipse. In this presentation we will show the status of the Quantum Fresco project, outline its future prospects and discuss its implications for Einstein Telescope.