Collectivity-assisted ground state cooling of a nanomechanical resonator

TL;DR

This paper proposes a method to cool a nanomechanical resonator to its ground state by leveraging collective effects in two interacting flux qubits, enhancing cooling efficiency through sub-radiant states and energy shifts.

Contribution

It introduces a novel cooling scheme utilizing collective qubit states to improve ground state cooling of nanomechanical resonators.

Findings

Cooling transitions via sub-radiant Dicke states reduce phonon number.

Collective energy shifts suppress detrimental carrier excitations.

Enhanced cooling efficiency compared to individual qubit systems.

Abstract

We discuss cooling of a nanomechanical resonator to its mechanical ground state by coupling it to a collective system of two interacting flux qubits. We find that the collectivity crucially improves cooling by two mechanisms. First, cooling transitions proceed via sub-radiant Dicke states, and the reduced line width of these sub-radiant states suppresses both the scattering and the environmental contribution to the final phonon number. Second, detrimental carrier excitations without change in the motion of the resonator are suppressed by collective energy shifts.