Coherent feedback cooling of a nanomechanical membrane with atomic spins

TL;DR

This paper demonstrates room-temperature coherent feedback cooling of a nanomechanical membrane using atomic spins, achieving significant phonon reduction and exploring delayed feedback effects, paving the way for quantum ground state cooling.

Contribution

It introduces a novel method of using optical coherent feedback with atomic spins to cool a nanomechanical membrane without measurement backaction.

Findings

Achieved cooling of membrane to 216 mK with 2.300 phonons.

Performed spin-membrane state swaps and spin pumping for cooling.

Studied effects of delayed feedback on cooling performance.

Abstract

Coherent feedback stabilises a system towards a target state without the need of a measurement, thus avoiding the quantum backaction inherent to measurements. Here, we employ optical coherent feedback to remotely cool a nanomechanical membrane using atomic spins as a controller. Direct manipulation of the atoms allows us to tune from strong-coupling to an overdamped regime. Making use of the full coherent control offered by our system, we perform spin-membrane state swaps combined with stroboscopic spin pumping to cool the membrane in a room-temperature environment to ${T}={216}\,\mathrm{mK}$ ($\bar{n}_{m} = 2.3\times 10^3$ phonons) in ${200}\,\mathrm{{\mu}s}$. We furthermore observe and study the effects of delayed feedback on the cooling performance. Starting from a cryogenically pre-cooled membrane, this method would enable cooling of the mechanical oscillator close to its quantum mechanical ground state and the preparation of nonclassical states.