Spectral Analysis of Quantum Field Fluctuations in a Strongly Coupled Optomechanical System

TL;DR

This paper demonstrates how a strongly coupled quantum optomechanical system can act as a broadband quantum spectrum analyzer, revealing quantum fluctuations and suppressing back-action through interference.

Contribution

It introduces a novel experimental approach to analyze quantum fluctuations across a wide spectral range in a strongly coupled optomechanical system.

Findings

Oscillator functions as a broadband quantum spectrum analyzer.

Spectral asymmetry reveals quantum fluctuations in cavity field.

Quantum back-action is suppressed in a narrow spectral region.

Abstract

With a levitodynamics experiment in the strong and coherent quantum optomechanical coupling regime, we demonstrate that the oscillator acts as a broadband quantum spectrum analyzer. The asymmetry between positive and negative frequency branches in the displacement spectrum traces out the spectral features of the quantum fluctuations in the cavity field, which are thus explored over a wide spectral range. Moreover, in our two-dimensional mechanical system the quantum back-action, generated by such vacuum fluctuations, is strongly suppressed in a narrow spectral region due to a destructive interference in the overall susceptibility.