Charging optimization of quantum battery via phase-controlled coherent ancillae
Phys. Rev. A 113, 052437 – Published 15 May, 2026
DOI: https://doi.org/10.1103/39yj-zgwf
Abstract
Quantum batteries (QBs) represent a promising platform for the storage and controlled release of energy through the principle of quantum mechanics. By investigating a multilevel QB charged by a sequence of coherent two-level atomic pairs (ancillae), with each atom carrying its own local coherence phase (LCP), we reveal that the coherence phases can be harnessed to optimize the charging dynamics. Specifically, based on the quantum master equation, we show that the charging dynamics of the QB is sensitive to the intra-ancilla LCP difference, while insensitive to their sum. Furthermore, we numerically demonstrate that the ergotropy oscillations can be induced by the coherence of ancilla during charging. Notably, the ergotropy at the first peak always remains at its maximum value, which is in trade-off with the value at saturation. Additionally, we found that the ergotropy oscillations can be effectively suppressed by increasing the LCP difference. And, the antiphase ancillae with maximal LCP difference can diminish the ergotropy oscillations, resulting in a stable charging. In contrast, the in-phase ancillae with minimal LCP difference can lead to the most pronounced ergotropy oscillations, and the first peak remains the highest. These features suggest two distinct operational charging modes: a long-term stable charging mode (charging QB saturation state) using antiphase ancillae and a short-term rapid charging mode (charging QB to the first ergotropy peak) using in-phase ancillae. We have verified that under the optimal short-term rapid charging mode, the overall performance (including ergotropy, charging power, and efficiency) of the coherent QB (CQB) is positively correlated with the battery size (i.e., the number of energy levels of the QB) and is always superior to that of its classical counterpart (i.e., thermal quantum battery, TQB); while under the optimal long-term stable charging mode, although the ergotropy of the CQB also increases monotonically with battery size and exceeds that of the TQB, the charging power and efficiency oscillate with the parity (odd-even) of the battery size, and the odd-sized CQBs outperform the even-sized CQBs. This work highlights coherence phases as a thermodynamic resource for improving the charging performance of QBs and suggests a potential approach to optimizing the design of other quantum devices.
