# Universal Coherence-Induced Power Losses of Quantum Heat Engines in Linear Response

## TL;DR

This paper presents a universal framework for analyzing power losses in quantum heat engines caused by quantum coherence, deriving bounds and demonstrating that coherence can lead to power reduction in the linear-response regime.

## Contribution

It introduces a universal scheme to separate classical and quantum coherence contributions to power, deriving bounds and showing coherence-induced power losses in linear response.

## Key findings

- Quantum coherence can cause power losses in heat engines.
- Derived bounds on coherent and total power outputs.
- Single-qubit engine example illustrates the theory.

## Abstract

We introduce a universal scheme to divide the power output of a periodically driven quantum heat engine into a classical contribution and one stemming solely from quantum coherence. Specializing to Lindblad-dynamics and small driving amplitudes, we derive general upper bounds on both, the coherent and the total power. These constraints imply that, in the linear-response regime, coherence inevitably leads to power losses. To illustrate our general analysis, we explicitly work out the experimentally relevant example of a single-qubit engine.