Quantum nondemolition measurement of a nonclassical state of a massive object

TL;DR

This paper demonstrates a quantum nondemolition measurement of a nonclassical state of a mechanical object using a microwave optomechanical system, advancing the ability to observe and stabilize fragile quantum states in larger systems.

Contribution

It introduces a method to prepare and measure nonclassical states of a massive object nondestructively, enabling exploration of quantum mechanics at larger scales.

Findings

Successfully stabilized a nonclassical steady-state of motion.

Performed a QND measurement of sub-vacuum quadrature fluctuations.

Demonstrated coupling of mechanical motion to microwave cavities for quantum state control.

Abstract

While quantum mechanics exquisitely describes the behavior of microscopic systems, one ongoing challenge is to explore its applicability to systems of larger size and mass. Unfortunately, quantum states of increasingly macroscopic objects are more easily corrupted by unintentional measurements from the classical environment. Additionally, even the intentional measurements from the observer can further perturb the system. In optomechanics, coherent light fields serve as the intermediary between the fragile mechanical states and our inherently classical world by exerting radiation pressure forces and extracting mechanical information. Here we engineer a microwave cavity optomechanical system to stabilize a nonclassical steady-state of motion while independently, continuously, and nondestructively monitoring it. By coupling the motion of an aluminum membrane to two microwave cavities, we separately prepare and measure a squeezed state of motion. We demonstrate a quantum nondemolition (QND) measurement of sub-vacuum mechanical quadrature fluctuations. The techniques developed here have direct applications in the areas of quantum-enhanced sensing and quantum information processing, and could be further extended to more complex quantum states.