Entangled massive mechanical oscillators

TL;DR

This paper reports the experimental creation and verification of entanglement between two macroscopic mechanical oscillators, advancing quantum technology and understanding of quantum mechanics at larger scales.

Contribution

The first experimental demonstration of steady-state entanglement between two massive mechanical oscillators coupled via a microwave cavity.

Findings

Successfully created entanglement between two micromechanical oscillators.

Verified entanglement through correlated mechanical fluctuations and microwave emission analysis.

Extended entanglement studies to macroscopic, massive objects.

Abstract

An entangled quantum state of two or more particles or objects exhibits some of the most peculiar features of quantum mechanics. Entangled systems cannot be described independently of each other even though they may have an arbitrarily large spatial separation. Reconciling this property with the inherent uncertainty in quantum states is at the heart of some of the most famous debates in the development of quantum theory. Nonetheless, entanglement nowadays has a solid theoretical and experimental foundation, and it is the crucial resource behind many emerging quantum technologies. Entanglement has been demonstrated for microscopic systems, such as with photons, ions, and electron spins, and more recently in microwave and electromechanical devices. For macroscopic objects, however, entanglement becomes exceedingly fragile towards environmental disturbances. A major outstanding goal has been to create and verify the entanglement between the motional states of slowly-moving massive objects. Here, we carry out such an experimental demonstration, with the moving bodies realized as two micromechanical oscillators coupled to a microwave-frequency electromagnetic cavity that is used to create and stabilise the entanglement of the centre-of-mass motion of the oscillators. We infer the existence of entanglement in the steady state by combining measurement of correlated mechanical fluctuations with an analysis of the microwaves emitted from the cavity. Our work qualitatively extends the range of entangled physical systems, with implications in quantum information processing, precision measurement, and tests of the limits of quantum mechanics.