Conditional Motional Squeezing of an Optomechanical Oscillator Approaching the Quantum Regime

TL;DR

This paper demonstrates a measurement-based protocol to conditionally prepare a macroscopic optomechanical oscillator in a classical squeezed state, approaching quantum limits, with significant reduction in uncertainty compared to previous methods.

Contribution

It shows that with optimal parameters and filtering, a classical squeezed state can be prepared in a macroscopic oscillator, advancing towards quantum squeezing.

Findings

Achieved a minimum uncertainty of 1.07 times the zero-point fluctuation level.

Demonstrated a three-orders-of-magnitude improvement over previous experiments.

Provided evidence that measurement-based protocols are practical for quantum state preparation.

Abstract

Squeezed mechanical states are a highly coveted resource for quantum-enhanced sensing and serve as a compelling platform for probing the interplay between gravity and quantum mechanics. It has been predicted that a mechanical oscillator can be prepared into a quantum squeezed state if the applied measurement rate is fast relative to its mechanical resonance frequency. However, the experimental feasibility of this protocol has remained uncertain because of the difficulty in achieving low-frequency oscillators with sufficiently strong read-out. Here, we demonstrate that a careful selection of parameters in an optomechanical system, combined with optimal filtering techniques, enables the preparation of a 50 ng GaAs cantilever in a conditional classical squeezed state, achieving a minimum uncertainty of just 1.07 plus/minus 0.04 times the zero-point fluctuation level. This minimum variance is 3 orders of magnitude smaller than what has been achieved in previous experiments using the same protocol. Although we do not fully achieve the quantum squeezed regime, our demonstration provides definitive evidence that a measurement-based protocol is a practical and effective approach for the real-time preparation of macroscopic oscillators in quantum squeezed states.