Quantum Fuel with Multilevel Atomic Coherence for Ultrahigh Specific Work in a Photonic Carnot Engine

TL;DR

This paper explores how multilevel quantum coherence in atomic systems enhances the work output and efficiency of photonic Carnot engines, demonstrating quadratic scaling and potential for overcoming decoherence in practical setups.

Contribution

It generalizes the phaseonium fuel to N+1 level atoms, analytically derives scaling laws, and shows how quantum coherence boosts engine performance beyond classical limits.

Findings

Efficiency and work scale quadratically with the number of coherent levels.

Quantum coherence significantly increases specific energy output.

Multilevel phaseonium fuel can mitigate decoherence in current resonator systems.

Abstract

We investigate scaling of work and efficiency of a photonic Carnot engine with the number of quantum coherent resources. Specifically, we consider a generalization of the "phaseonium fuel" for the photonic Carnot engine, which was first introduced as a three-level atom with two lower states in a quantum coherent superposition by [M. O. Scully, M. Suhail Zubairy, G. S. Agarwal, and H. Walther, Science {\bf 299}, 862 (2003)], to the case of $N+1$ level atoms with $N$ coherent lower levels. We take into account atomic relaxation and dephasing as well as the cavity loss and derive a coarse grained master equation to evaluate the work and efficiency, analytically. Analytical results are verified by microscopic numerical examination of the thermalization dynamics. We find that efficiency and work scale quadratically with the number of quantum coherent levels. Quantum coherence boost to the specific energy (work output per unit mass of the resource) is a profound fundamental difference of quantum fuel from classical resources. We consider typical modern resonator set ups and conclude that multilevel phaseonium fuel can be utilized to overcome the decoherence in available systems. Preparation of the atomic coherences and the associated cost of coherence are analyzed and the engine operation within the bounds of the second law is verified. Our results bring the photonic Carnot engines much closer to the capabilities of current resonator technologies.