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.
@article{arxiv.2604.04873,
title = {Driving Quantum Heat Engines Beyond Classical Limits through Multilevel Coherence},
author = {Hui Wang and Yusef Maleki and William J. Munro and Marlan O. Scully},
journal= {arXiv preprint arXiv:2604.04873},
year = {2026}
}