Thermodynamics of a Quantum Annealer

TL;DR

This paper investigates the thermodynamic behavior of D-Wave quantum annealers, revealing how they operate as thermal machines with quantifiable heat, work, and dissipation during reverse annealing processes.

Contribution

It applies non-equilibrium thermodynamics to experimental data from D-Wave annealers to quantify heat, work, and dissipation, providing new insights into their thermodynamic properties.

Findings

D-Wave acts as a thermal accelerator during reverse annealing

Dissipation increases with transverse field strength

Quantifies heat and work exchanges using fluctuation theorem and thermodynamic uncertainty relations

Abstract

The D-wave processor is a partially controllable open quantum system which exchanges energy with its surrounding environment (in the form of heat) and with the external time dependent control fields (in the form of work). Despite being rarely thought as such, it is a thermodynamic machine. Here we investigate the properties of the D-Wave quantum annealers from a thermodynamical perspective. We performed a number of reverse-annealing experiments on the D-Wave 2000Q via the open access cloud server Leap, with the aim of understanding what type of thermal operation the machine performs, and quantifying the degree of dissipation that accompanies it, as well as the amount of heat and work that it exchanges. The latter is a challenging task in view of the fact that one can experimentally access only the overall energy change occurring in the processor, (which is the sum of heat and work it receives). However, recent results of non-equilibrium thermodynamics(namely, the fluctuation theorem and the thermodynamic uncertainty relations), allow to calculate lower bounds on the average entropy production (which quantifies the degree of dissipation) as well as the average heat and work exchanges. The analysis of the collected experimental data shows that 1) in a reverse annealing process the D-Wave processor works as a thermal accelerator and 2) its evolution involves an increasing amount of dissipation with increasing transverse field.