Super-Extensive Charging Power in the Absence of Global Operations

TL;DR

This paper identifies g-extensiveness as a key structural property necessary for superextensive charging power in quantum batteries, providing a framework to engineer systems with quantum advantage.

Contribution

It introduces g-extensiveness as a fundamental bound on charging performance and demonstrates its role in achieving superextensive power scaling in quantum batteries.

Findings

Superextensive power requires nonuniform interaction-energy distribution.

Many protocols fail to achieve superextensive power due to uniform energy distribution.

An experimentally relevant model exhibits superextensive charging power under the g-extensiveness condition.

Abstract

Quantum batteries have emerged as a platform for investigating whether quantum effects can accelerate energy storage beyond classical limits. Although a variety of charging schemes have reported signatures of quantum advantage, the fundamental physical requirements for achieving superextensive charging power remain insufficiently understood. Here, we show that, in addition to Hamiltonian locality, a key structural property, g-extensiveness, quantifying the distribution of interaction energy across lattice sites places a fundamental bound on charging performance in spin-lattice models. We prove that superextensive power scaling is possible only when the interaction-energy distribution becomes increasingly nonuniform, with the maximal local weight growing with system size. This criterion explains why many previously studied protocols fail to exhibit superextensive power, even when the Hamiltonians involve large participation numbers. We further demonstrate that this condition is realized in an experimentally relevant interacting model, where, despite fixed interaction order, the charging power scales superextensively. Our results establish g-extensiveness as a necessary resource for quantum advantage in direct-charging protocols and provide a systematic framework for identifying and engineering physically feasible quantum batteries capable of outperforming classical counterparts in charging power.