Domino cooling of a coupled mechanical-resonator chain via cold-damping feedback

TL;DR

This paper introduces a domino-cooling method for simultaneously cooling multiple coupled mechanical resonators to their ground states using optomechanical feedback, even in the unresolved-sideband regime, enabling advanced quantum control.

Contribution

It presents a novel domino-effect cooling technique combining cold-damping feedback with mechanical coupling, effective in the unresolved-sideband regime, and demonstrates flexible control over cooling symmetry.

Findings

Effective ground-state cooling of coupled resonators achieved

Switchable symmetric/asymmetric cooling via feedback and laser power

Temperature gradient observed along the resonator chain

Abstract

We propose a domino-cooling method to realize simultaneous ground-state cooling of a coupled mechanical-resonator chain through an optomechanical cavity working in the unresolved-sideband regime. This domino-effect cooling is realized by combining the cold-damping feedback on the first mechanical resonator with nearest-neighbor couplings between other neighboring mechanical resonators. We obtain analytical results for the effective susceptibilities, noise spectra, final mean phonon numbers, and cooling rates of these mechanical resonators, and find the optimal-cooling condition for these resonators. Particularly, we analyze a two-mechanical-resonator case and find that by appropriately engineering either the laser power or the feedback, a flexible switch between symmetric and asymmetric ground-state cooling can be achieved. This could be used for preparing symmetric quantum states in mechanical systems. We also simulate the cooling performance of a coupled $N$-mechanical-resonator chain and confirm that these resonators can be simultaneously cooled to their quantum ground states in the unresolved-sideband regime. Under proper parameter conditions, the cooling of the mechanical-resonator chain shows a temperature gradient along the chain. This study opens a route to quantum manipulation of multiple mechanical resonators in the bad-cavity regime.