Periodically refreshed quantum thermal machines

TL;DR

This paper introduces a new class of quantum thermal machines that operate optimally at finite cycle durations by leveraging non-equilibrium steady states, bridging different models and revealing trade-offs between performance and implementation complexity.

Contribution

The paper proposes a novel class of cyclic quantum thermal machines based on Periodically Refreshed Baths, unifying collisional and autonomous QTMs, and provides a mathematical framework for Gaussian systems.

Findings

Maximal performance occurs at finite cycle duration where the process is most irreversible.

Implementation complexity increases with performance optimization, requiring more bath copies.

Connections are established between the PReB process and Zeno effects.

Abstract

We introduce unique class of cyclic quantum thermal machines (QTMs) which can maximize their performance at the finite value of cycle duration $\tau$ where they are most irreversible. These QTMs are based on single-stroke thermodynamic cycles realized by the non-equilibrium steady state (NESS) of the so-called Periodically Refreshed Baths (PReB) process. We find that such QTMs can interpolate between standard collisional QTMs, which consider repeated interactions with single-site environments, and autonomous QTMs operated by simultaneous coupling to multiple macroscopic baths. We discuss the physical realization of such processes and show that their implementation requires a finite number of copies of the baths. Interestingly, maximizing performance by operating in the most irreversible point as a function of $\tau$ comes at the cost of increasing the complexity of realizing such a regime, the latter quantified by the increase in the number of copies of baths required. We demonstrate this physics considering a simple example. We also introduce an elegant description of the PReB process for Gaussian systems in terms of a discrete-time Lyapunov equation. Further, our analysis also reveals interesting connections with Zeno and anti-Zeno effects.