Quantum back-action evading measurement of collective mechanical modes

TL;DR

This paper demonstrates quantum back-action evading measurements of a collective quadrature of two mechanical oscillators coupled to a microwave cavity, enabling precise quantum state tomography and advancing macroscopic entanglement and force sensing.

Contribution

It introduces a method for quantum back-action evading measurement of collective mechanical modes, surpassing standard quantum limits for precision.

Findings

Successful measurement of a collective quadrature of two mechanical oscillators

Enables quantum state tomography of mechanical systems

Provides a basis for macroscopic entanglement and enhanced force sensing

Abstract

The standard quantum limit constrains the precision of an oscillator position measurement. It arises from a balance between the imprecision and the quantum back-action of the measurement. However, a measurement of only a single quadrature of the oscillator can evade the back-action and be made with arbitrary precision. Here we demonstrate quantum back-action evading measurements of a collective quadrature of two mechanical oscillators, both coupled to a common microwave cavity. The work allows for quantum state tomography of two mechanical oscillators, and provides a foundation for macroscopic mechanical entanglement and force sensing beyond conventional quantum limits.