Squeezed-light interferometry on a cryogenically-cooled micro-mechanical membrane

TL;DR

This paper demonstrates the use of squeezed light for enhanced position sensing of a cryogenically cooled micro-mechanical membrane, achieving significant noise reduction and paving the way for advanced gravitational-wave detectors.

Contribution

It presents the first experimental demonstration of squeezed-light position sensing on a cryo-cooled membrane, showing improved sensitivity and feasibility for cryogenic interferometry.

Findings

Achieved up to 4.8 dB noise reduction below photon counting noise.

Demonstrated high interference contrast in a cryogenic Michelson interferometer.

Showed potential for application in future gravitational-wave detectors.

Abstract

Squeezed states of light reduce the signal-normalized photon counting noise of measurements without increasing the light power and enable fundamental research on quantum entanglement in hybrid systems of light and matter. Furthermore, the completion of squeezed states with cryo-cooling has high potential. First, measurement sensitivities are usually limited by quantum noise and thermal noise. Second, squeezed states allow for reducing the heat load on cooled devices without losing measurement precision. Here, we demonstrate squeezed-light position sensing of a cryo-cooled micro-mechanical membrane. The sensing precision is improved by up to 4.8 dB below photon counting noise, limited by optical loss in two Faraday rotators, at a membrane temperature of about 20K, limited by our cryo-cooler. We prove that realising a high interference contrast in a cryogenic Michelson interferometer is feasible. Our setup is the first conceptual demonstration towards the envisioned European gravitational-wave detector, the 'Einstein Telescope', which is planned to use squeezed states of light together with cryo-cooling of its mirror test masses.