# Quantum limit to nonequilibrium heat-engine performance imposed by strong system-reservoir coupling

## TL;DR

This paper demonstrates that strong system-reservoir coupling in quantum heat engines imposes a fundamental quantum limit on their efficiency and power, due to induced coherence that cannot be described by standard models.

## Contribution

It reveals a quantum limit on heat-engine performance caused by finite system-reservoir coupling, highlighting the role of coherence beyond traditional approximations.

## Key findings

- Finite coupling induces coherence that hampers engine performance.
- Standard Born-Markov analysis fails to capture these effects.
- Quantum limit constrains efficiency and power output.

## Abstract

We show that finite system-reservoir coupling imposes a distinct quantum limit on the performance of a non-equilibrium quantum heat engine. Even in the absence of quantum friction along the isentropic strokes, finite system-reservoir coupling induces correlations that result in the generation of coherence between the energy eigenstates of the working system. This coherence acts to hamper the engine's power output, as well as the efficiency with which it can convert heat into useful work, and cannot be captured by a standard Born-Markov analysis of the system-reservoir interactions.