Path-Degenerate Quantum Interferometry for Decoherence Mitigation in Gravitational-Wave Detectors

Abstract:Optical decoherence degrades quantum correlations in squeezed states of light, severely limiting the quantum-nondemolition (QND) sensitivity of gravitational-wave detectors. Here, we propose the path-degenerate quantum interferometry scheme that obviates the need for entire optical subsystems---including additional filter cavities, auxiliary parametric amplifiers, and Faraday isolators---thereby drastically reducing spatial mode mismatches while inherently integrating variational output, a long-standing theoretical proposal to further deepen the QND regime. We experimentally demonstrate a core aspect of this scheme, achieving a shot-noise-preserving signal enhancement that directly counteracts the detrimental effects of readout loss. By delivering an improved signal-to-quantum-noise ratio solely through the consolidation and reduction of currently considered optical subsystems, our approach offers a highly optimized route toward enhanced quantum-noise reduction in upcoming LIGO upgrades and next-generation gravitational-wave observatories.

Quantum Physics (quant-ph); Instrumentation and Methods for Astrophysics (astro-ph.IM); Optics (physics.optics)

arXiv:2609.12204 [quant-ph]

(or arXiv:2609.12204v1 [quant-ph] for this version)

https://doi.org/10.48550/arXiv.2609.12204 Focus to learn more arXiv-issued DOI via DataCite (pending registration)

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