Observation of Radiation Pressure Shot Noise on a Macroscopic Object

TL;DR

This paper reports the first observation of radiation pressure shot noise on a macroscopic mechanical resonator, demonstrating quantum backaction consistent with Heisenberg's uncertainty principle and correlating radiation force fluctuations with resonator position.

Contribution

It provides the first experimental evidence of radiation pressure shot noise affecting a macroscopic object, confirming quantum measurement limits in optomechanics.

Findings

Radiation pressure shot noise observed on a macroscopic resonator

Backaction force matches quantum uncertainty predictions

Temporal correlations between radiation force and resonator position detected

Abstract

The quantum mechanics of position measurement of a macroscopic object is typically inaccessible because of strong coupling to the environment and classical noise. Here we monitor a mechanical resonator subject to an increasingly strong continuous position measurement and observe a quantum mechanical backaction force that rises in accordance with the Heisenberg uncertainty limit. For our optically-based position measurements, the backaction takes the form of a fluctuating radiation pressure from the Poisson-distributed photons in the coherent measurement field, termed radiation pressure shot noise. We demonstrate a backaction force that is comparable in magnitude to the thermal forces in our system. Additionally, we observe a temporal correlation between fluctuations in the radiation force and in the position of the resonator.