Strong Thermomechanical Noise Squeezing Stabilized by Feedback

TL;DR

This paper demonstrates record-high thermomechanical squeezing of silicon nitride membrane resonators using feedback stabilization, achieving up to 21 dB, with implications for quantum sensing at cryogenic temperatures.

Contribution

It introduces a feedback stabilization method to surpass traditional squeezing limits, achieving record thermomechanical squeezing levels in high-Q membrane resonators.

Findings

Achieved 17 dB and 21 dB squeezing with piezo and capacitive modulation.

Proposed that larger squeezing is possible with minimal device modifications.

Quantum squeezing could be realized at moderate cryogenic temperatures.

Abstract

Squeezing the quadrature noise of a harmonic oscillator used as a sensor can enhance its sensitivity in certain measurment schemes. The canonical approach, based on parametric modulation of the oscillation frequency, is usually limited to a squeezing of at most 3 dB. However, this can be overcome by additional stabilization of the anti-squeezed quadrature. Here, we apply this approach to highly-stressed silicon nitride membrane resonators, with effective masses of the order few nanograms and quality factors routinely exceeding 108, which hold promise for sensing applications in both the classical and quantum regimes. We benchmark their performance using either piezo or capacitive parametric modulation. We observe maximum thermomechanical squeezing by record-high 17 dB and 21 dB, respectively, and we argue that even larger values can be attained with minimal changes to the device design. Finally, we provide a full quantum theory of a combination of this approach with quantum-limited motion measurement and conclude that quantum squeezing is attainable at moderate cryogenic temperatures.