Resolving the vacuum fluctuations of an optomechanical system using an artificial atom

Abstract

Vacuum fluctuations in a ground-state mechanical oscillator are hard to distinguish from noise, but by using the coupling with a superconducting qubit in a microwave cavity one can amplify and convert them to directly measurable real photons. Heisenberg’s uncertainty principle results in one of the strangest quantum behaviours: a mechanical oscillator can never truly be at rest. Even at a temperature of absolute zero, its position and momentum are still subject to quantum fluctuations1,2. However, direct energy detection of the oscillator in its ground state makes it seem motionless1,3, and in linear position measurements detector noise can masquerade as mechanical fluctuations4,5,6,7. Thus, how can we resolve quantum fluctuations? Here, we parametrically couple a micromechanical oscillator to a microwave cavity to prepare the system in its quantum ground state8,9 and then amplify the remaining vacuum fluctuations into real energy quanta10. We monitor the photon/phonon-number distributions using a superconducting qubit11,12,13, allowing us to resolve the quantum vacuum fluctuations of the macroscopic oscillator’s motion. Our results further demonstrate the ability to control a long-lived mechanical oscillator using a non-Gaussian resource, directly enabling applications in quantum information processing and enhanced detection of displacement and forces.