Hamiltonian $k$-Locality is the Key Resource for Powerful Quantum Battery Charging

TL;DR

This paper identifies that the key to powerful quantum battery charging lies in the Hamiltonian's locality and energy capacity, rather than entanglement, providing a new theoretical bound for system design.

Contribution

It introduces a new upper bound on quantum battery charging power based on Hamiltonian locality and energy capacity, challenging the emphasis on entanglement.

Findings

Locality of Hamiltonians is crucial for charging power.

Maximum energy per unit cell limits charging speed.

Entanglement is less critical than previously believed.

Abstract

Storing and extracting energy using quantum degrees of freedom is a promising approach to leveraging quantum effects in energy science. Early experimental efforts have already demonstrated its potential to surpass the charging power of existing technologies. In this context, it is crucial to identify the specific quantum effects that can be exploited to design the most efficient quantum batteries and push their performance to the ultimate limit. While entanglement has often been considered a key factor in enhancing charging (or discharging) power, our findings reveal that it is not as critical as previously thought. Instead, three parameters emerge as the most significant in determining the upper bound of instantaneous charging power: the locality of the battery and charger Hamiltonians, and the maximum energy storable in a single unit cell of the battery. To derive this new bound, we have also addressed several open questions previously noted in the literature but lacks an explanation. This bound provides a foundation for designing the most powerful charger-battery systems, where combined optimization of both components offers enhancements that cannot be achieved by manipulating only one of them.