Driving Quantum Heat Engines Beyond Classical Limits through Multilevel Coherence

TL;DR

This paper demonstrates how multilevel quantum coherence can be used to control the effective temperature of quantum heat engines, enabling enhanced efficiency and tunability beyond classical limits.

Contribution

It derives analytic expressions for temperature control via N-level coherence and unifies ground- and excited-state coherence effects in a single framework.

Findings

Quantum coherence can tune the effective temperature from near-zero to divergence.

Ground- and excited-state coherence interplay enables thermodynamic control.

Rubidium atoms are identified as candidates for experimental realization.

Abstract

Quantum coherence provides a controllable thermodynamic resource that can raise or lower the effective temperature of a cavity mode, enabling efficiency tuning in quantum heat engines. Here, we derive analytic expressions for the effective engine temperature, demonstrating the enhanced temperature tunability achievable via $N$-level ground-state coherence. We further unify ground- and excited-state coherence within a single analytic framework, revealing their interplay as a mechanism for thermodynamic control. Such quantum resources serve as tunable parameters that enable switching between heating, cooling, and cancellation regimes, driving the effective temperature from near-zero to divergence. Ultimately, our framework connects and generalizes previous models of quantum heat engines, and we identify rubidium atoms as a promising candidate for experimentally realizing these coherence-assisted effects.