Resolved-sideband cooling and measurement of a micromechanical oscillator close to the quantum limit

TL;DR

This paper demonstrates near-quantum ground state cooling and high-precision measurement of a mesoscopic mechanical oscillator using cavity optomechanics, advancing the exploration of quantum phenomena in macroscopic objects.

Contribution

First to achieve resolved-sideband cooling and near-quantum-limited measurement on a mesoscopic oscillator with mass much larger than nano-mechanical systems.

Findings

Prepared oscillator close to ground state with 63±20 phonons

Achieved measurement sensitivity within a factor of 5.5 of the quantum limit

Demonstrated quantum regime in a visibly large mechanical object

Abstract

The observation of quantum phenomena in macroscopic mechanical oscillators has been a subject of interest since the inception of quantum mechanics. Prerequisite to this regime are both preparation of the mechanical oscillator at low phonon occupancy and a measurement sensitivity at the scale of the spread of the oscillator's ground state wavefunction. It has been widely perceived that the most promising approach to address these two challenges are electro nanomechanical systems. Here we approach for the first time the quantum regime with a mechanical oscillator of mesoscopic dimensions--discernible to the bare eye--and 1000-times more massive than the heaviest nano-mechanical oscillators used to date. Imperative to these advances are two key principles of cavity optomechanics: Optical interferometric measurement of mechanical displacement at the attometer level, and the ability to use measurement induced dynamic back-action to achieve resolved sideband laser cooling of the mechanical degree of freedom. Using only modest cryogenic pre-cooling to 1.65 K, preparation of a mechanical oscillator close to its quantum ground state (63+-20 phonons) is demonstrated. Simultaneously, a readout sensitivity that is within a factor of 5.5+-1.5 of the standard quantum limit is achieved. The reported experiments mark a paradigm shift in the approach to the quantum limit of mechanical oscillators using optical techniques and represent a first step into a new era of experimental investigation which probes the quantum nature of the most tangible harmonic oscillator: a mechanical vibration.