Testing a Quantum Heat Pump with a Two-Level Spin

TL;DR

This paper proposes a method to test and diagnose quantum heat pumps using a two-level spin probe, enabling insights into their heat flow, leaks, and efficiency without detailed internal knowledge.

Contribution

It introduces a black-box testing strategy for quantum heat pumps using a two-level spin, allowing performance assessment and internal dissipation detection.

Findings

The steady state of the probe reveals heat leaks and dissipation.

The method estimates the heat pump's coefficient of performance.

Applicable to complex quantum thermal systems.

Abstract

Once in its non-equilibrium steady state, a nanoscale system coupled to several heat baths may be thought-of as a quantum heat pump. Depending on the direction of its stationary heat flows it may function as e.g. a refrigerator or a heat transformer. These continuous heat devices can be arbitrarily complex multipartite systems, and yet their working principle is always the same: They are made up of several elementary three-level stages operating in parallel. As a result, it is possible to devise external black-box testing strategies to learn about their functionality and performance regardless of any internal details. In particular, one such heat pump can be tested by coupling a two-level spin to one of its contact transitions. The steady state of this external probe contains information about the presence of heat leaks and internal dissipation in the device, and also, about the direction of its steady-state heat currents. Provided that the irreversibility of the heat pump is low, one can further estimate its coefficient of performance. These techniques may find applications in the emerging field of quantum thermal engineering, as they facilitate the diagnosis and design optimization of complex thermodynamic cycles.