Quantum Enhancement of the Zero-Area Sagnac Interferometer Topology for Gravitational Wave Detection

TL;DR

This paper demonstrates that a zero-area Sagnac interferometer, enhanced with squeezed light, can achieve quantum nondemolition measurements and surpass the standard quantum limit, offering a promising approach for future gravitational wave detectors.

Contribution

The study experimentally shows that squeezed light can significantly enhance the sensitivity of a zero-area Sagnac interferometer for gravitational wave detection.

Findings

Achieved 8.2 dB sensitivity improvement with squeezed light.

Measured 12.7 dB squeezing directly from the laser output.

Surpassed the standard quantum limit across a broad frequency spectrum.

Abstract

Only a few years ago, it was realized that the zero-area Sagnac interferometer topology is able to perform quantum nondemolition measurements of position changes of a mechanical oscillator. Here, we experimentally show that such an interferometer can also be efficiently enhanced by squeezed light. We achieved a nonclassical sensitivity improvement of up to 8.2 dB, limited by optical loss inside our interferometer. Measurements performed directly on our squeezed-light laser output revealed squeezing of 12.7 dB. We show that the sensitivity of a squeezed-light enhanced Sagnac interferometer can surpass the standard quantum limit for a broad spectrum of signal frequencies without the need for filter cavities as required for Michelson interferometers. The Sagnac topology is therefore a powerful option for future gravitational-wave detectors, such as the Einstein Telescope, whose design is currently being studied.