The quest for absolute zero in presence of external noise

TL;DR

This paper investigates the limits of a quantum refrigerator approaching absolute zero in the presence of external noise, analyzing how noise impacts its cooling efficiency and the possibility of reaching zero temperature.

Contribution

It introduces a model of a quantum Otto cycle refrigerator with harmonic oscillators and studies the effects of external Gaussian noise on its performance near absolute zero.

Findings

External noise reduces the heat extraction capacity.

Zero temperature can still be approached despite noise.

Frictionless solutions are possible in noiseless conditions.

Abstract

A reciprocating quantum refrigerator is analyzed with the intention to study the limitations imposed by external noise. In particular we focus on the behavior of the refrigerator when it approaches the absolute zero. The cooling cycle is based on the Otto cycle with a working medium constituted by an ensemble of non interacting harmonic oscillators. The compression and expansion segments are generated by changing an external parameter in the Hamiltonian. In this case the force constant of the harmonic oscillators $m \omega^2$ is modified from an initial to a final value. As a result, the kinetic and potential energy of the system do not commute causing frictional losses. By proper choice of scheduling function $\omega(t)$ frictionless solutions can be obtained in the noiseless case. We examine the performance of a refrigerator subject to noise. By expanding from the adiabatic limit we find that the external noise, gaussian phase and amplitude noises, reduce the amount of heat that can be extracted but nevertheless the zero temperature can be approached.