Mechanical parametric feedback-cooling for pendulum-based gravity experiments

TL;DR

This paper introduces a mechanical parametric feedback cooling method for pendulums used in gravity experiments, demonstrating significant damping and potential to reach quantum ground state conditions, with applications in gravitational-wave detection.

Contribution

It presents a novel mechanical parametric feedback cooling technique for pendulums, achieving high damping factors and advancing toward quantum ground state conditions.

Findings

Achieved a damping factor of 5.7 in seismic noise conditions.

Demonstrated proof of principle for cooling near the quantum ground state.

Potential applications in gravitational-wave detectors.

Abstract

Gravitational forces that oscillate at audio-band frequencies are measured with masses suspended as pendulums that have resonance frequencies even lower. If the pendulum is excited by thermal energy or by seismic motion of the environment, the measurement sensitivity is reduced. Conventionally, this problem is mitigated by seismic isolation and linear damping, potentially combined with cryogenic cooling. Here, we propose mechanical parametric cooling of the pendulum motion during the gravitational field measurement. We report a proof of principle demonstration in the seismic noise dominated regime and achieve a damping factor of the pendulum motion of 5.7. We find a model system for which mechanical parametric feedback cooling reaches the quantum mechanical regime near the ground state. More feasible applications we anticipate in gravitational-wave detectors.