Nanomechanical motion measured with precision beyond the standard quantum limit

TL;DR

This paper demonstrates a measurement of nanomechanical motion surpassing the standard quantum limit by integrating a microwave optomechanical system with a nearly noiseless amplifier, achieving high sensitivity and advancing quantum entanglement prospects.

Contribution

The authors develop an integrated microwave optomechanical system with a nearly noiseless amplifier to measure motion below the standard quantum limit, enabling ultra-sensitive force detection.

Findings

Achieved measurement imprecision below the SQL.

Demonstrated force sensitivity of 0.51 aN/√Hz.

Enabled efficient quantum measurements for mechanical oscillators.

Abstract

Nanomechanical oscillators are at the heart of ultrasensitive detectors of force, mass and motion. As these detectors progress to even better sensitivity, they will encounter measurement limits imposed by the laws of quantum mechanics. For example, if the imprecision of a measurement of an oscillator's position is pushed below the standard quantum limit (SQL), quantum mechanics demands that the motion of the oscillator be perturbed by an amount larger than the SQL. Minimizing this quantum backaction noise and nonfundamental, or technical, noise requires an information efficient measurement. Here we integrate a microwave cavity optomechanical system and a nearly noiseless amplifier into an interferometer to achieve an imprecision below the SQL. As the microwave interferometer is naturally operated at cryogenic temperatures, the thermal motion of the oscillator is minimized, yielding an excellent force detector with a sensitivity of 0.51 aN/rt(Hz). In addition, the demonstrated efficient measurement is a critical step towards entangling mechanical oscillators with other quantum systems.