Quantum Model of Cooling and Force Sensing With an Optically Trapped Nanoparticle

TL;DR

This paper develops the first quantum theoretical framework for cooling and force sensing of optically trapped nanoparticles, revealing new mechanisms and guiding future experiments toward ground state preparation and ultra-weak force detection.

Contribution

It introduces a quantum model that predicts ground state cooling without an optical resonator and describes nonlinear friction as the cooling mechanism, aligning with experimental data.

Findings

Cooling can occur via nonlinear friction without an optical resonator.

Energy loss during cooling is nonexponential in time.

The model provides a framework for optimizing force sensing and approaching quantum limits.

Abstract

Optically trapped nanoparticles have recently emerged as exciting candidates for tests of quantum mechanics at the macroscale and as versatile platforms for ultrasensitive metrology. Recent experiments have demonstrated parametric feedback cooling, nonequilibrium physics, and temperature detection, all in the classical regime. Here we provide the first quantum model for trapped nanoparticle cooling and force sensing. In contrast to existing theories, our work indicates that the nanomechanical ground state may be prepared without using an optical resonator; that the cooling mechanism corresponds to nonlinear friction; and that the energy loss during cooling is nonexponential in time. Our results show excellent agreement with experimental data in the classical limit, and constitute an underlying theoretical framework for experiments aiming at ground state preparation. Our theory also addresses the optimization of, and the fundamental quantum limit to, force sensing, thus providing theoretical direction to ongoing searches for ultra-weak forces using levitated nanoparticles.