Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

# A broadband signal recycling scheme for saturating the quantum limit from optical losses

Version 1 : Received: 13 November 2020 / Approved: 16 November 2020 / Online: 16 November 2020 (09:10:41 CET)

How to cite: Zhang, T.; Bentley, J.; Miao, H. A broadband signal recycling scheme for saturating the quantum limit from optical losses. Preprints 2020, 2020110405 (doi: 10.20944/preprints202011.0405.v1). Zhang, T.; Bentley, J.; Miao, H. A broadband signal recycling scheme for saturating the quantum limit from optical losses. Preprints 2020, 2020110405 (doi: 10.20944/preprints202011.0405.v1).

## Abstract

Quantum noise limits the sensitivity of laser interferometric gravitational-wave detectors. Given the state-of-the-art optics, the optical losses define the lower bound of best possible quantum-limited detector sensitivity. In this work, we come up with the configuration which allows to saturate this lower bound by converting the signal recycling cavity to be a broadband signal amplifier using an active optomechanical filter. We will show the difference and advantage of such a broadband signal recycling scheme compared with the previous white-light-cavity scheme using the optomechanical filter in [Phys.Rev.Lett.115.211104 (2015)]. The drawback is that the new scheme is more susceptible to the thermal noise of the mechanical oscillator. To suppress the radiation pressure noise which rises along with the signal amplification, squeezing with input/output filter cavities and heavier test mass are used in this work.

## Subject Areas

quantum loss limit; broadband signal recycling; optomechanical filter cavity

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