Quantum correlations from a room-temperature optomechanical cavity

TLDR

Quantum measurement backaction perturbs an object's motion, but at room temperature its effect is usually overwhelmed by thermal motion, making it hard to detect. The experiment uses laser light on a nanomechanical beam to measure its thermal vibrations while inducing optical force fluctuations governed by the Heisenberg uncertainty principle. Using a cross‑correlation method, the authors separate optically driven motion from thermal noise and observe quantum backaction at room temperature, and they show that the magnitude of these quantum correlations can be used to calibrate thermal motion for absolute thermometry.

Abstract

The act of position measurement alters the motion of an object being measured. This quantum measurement backaction is typically much smaller than the thermal motion of a room-temperature object and thus difficult to observe. By shining laser light through a nanomechanical beam, we measure the beam's thermally driven vibrations and perturb its motion with optical force fluctuations at a level dictated by the Heisenberg measurement-disturbance uncertainty relation. We demonstrate a cross-correlation technique to distinguish optically driven motion from thermally driven motion, observing this quantum backaction signature up to room temperature. We use the scale of the quantum correlations, which is determined by fundamental constants, to gauge the size of thermal motion, demonstrating a path toward absolute thermometry with quantum mechanically calibrated ticks.