Observation of quantum-measurement backaction with an ultracold atomic gas

TL;DR

This paper demonstrates the first observation of quantum measurement backaction on a macroscopic system, using an ultracold atomic gas in an optical cavity to explore quantum mechanics at a large scale.

Contribution

It introduces a new experimental platform with ultracold atoms in a cavity to observe quantum backaction, advancing quantum measurement research.

Findings

First measurement of backaction at the standard quantum limit

Quantified cavity-light-induced heating of atomic ensemble

Established ultracold atomic gas as a macroscopic quantum system

Abstract

Current research on micro-mechanical resonators strives for quantum-limited detection of the motion of macroscopic objects. Prerequisite to this goal is the observation of measurement backaction consistent with quantum metrology limits. However, thermal noise presently dominates measurements and precludes ground-state preparation of the resonator. Here we establish the collective motion of an ultracold atomic gas confined tightly within a Fabry-Perot optical cavity as a system for investigating the quantum mechanics of macroscopic bodies. The cavity-mode structure selects a single collective vibrational mode that is measured by the cavity's optical properties, actuated by the cavity optical field, and subject to backaction by the quantum force fluctuations of this field. Experimentally, we quantify such fluctuations by measuring the cavity-light-induced heating of the intracavity atomic ensemble. These measurements represent the first observation of backaction on a macroscopic mechanical resonator at the standard quantum limit.