Artificial quantum thermal bath: Engineering temperature for a many-body quantum system

TL;DR

This paper introduces a method to engineer a quantum bath that can set a quantum system's temperature independently of its environment, enabling simulation of thermodynamics in many-body quantum systems and applications in quantum annealing.

Contribution

The paper develops a theoretical framework and proposes a circuit-QED implementation for an engineered quantum thermal bath with tunable temperature.

Findings

Proposes criteria for an engineered quantum bath to control system temperature.

Designs a circuit-QED setup with driven lossy resonators to realize the thermal bath.

Enables simulation of thermodynamics in larger quantum systems beyond classical capabilities.

Abstract

Temperature determines the relative probability of observing a physical system in an energy state when that system is energetically in equilibrium with its environment. In this paper, we present a theory for engineering the temperature of a quantum system different from its ambient temperature. We define criteria for an engineered quantum bath that, when coupled to a quantum system with Hamiltonian $H$, drives the system to the equilibrium state $\frac{e^{-H/T}}{{{\rm{Tr}}}(e^{-H/T})}$ with a tunable parameter $T$. This is basically an analog counterpart of the digital quantum metropolis algorithm. For a system of superconducting qubits, we propose a circuit-QED approximate realization of such an engineered thermal bath consisting of driven lossy resonators. Our proposal opens the path to simulate thermodynamical properties of many-body quantum systems of size not accessible to classical simulations. Also we discuss how an artificial thermal bath can serve as a temperature knob for a hybrid quantum-thermal annealer.