Quantum collective motion of macroscopic mechanical oscillators

TL;DR

This paper demonstrates quantum collective motion in a system of six macroscopic mechanical oscillators, showing enhanced coupling and ground state preparation, paving the way for multi-partite entanglement and quantum metrology applications.

Contribution

The study achieves the first observation of quantum collective behavior in multiple macroscopic oscillators within a superconducting circuit platform, with a $ oot{N}$ coupling enhancement.

Findings

Realization of quantum regime for six mechanical oscillators

Observation of $ oot{N}$ enhancement in collective coupling

Preparation of collective mode in quantum ground state

Abstract

Collective phenomena arise from interactions within complex systems, leading to behaviors absent in individual components. Observing quantum collective phenomena with macroscopic mechanical oscillators has been impeded by the stringent requirement that oscillators be identical. Here, we demonstrate the quantum regime for collective motion of $N=6$ mechanical oscillators, a hexamer, in a superconducting circuit optomechanical platform. By increasing the optomechanical couplings, the system transitions from individual to collective motion, characterized by a $\sqrt{N}$ enhancement of cavity-collective mode coupling, akin to super-radiance of atomic ensembles. Using sideband cooling, we prepare the collective mode in the quantum ground state and measure its quantum sideband asymmetry, with zero-point motion distributed across distant oscillators. This regime of optomechanics opens avenues for studying multi-partite entanglement, with potential advances in quantum metrology.