Anass Jad | Searcharxiv

arXiv2026

Suppressing Self-Discharging of Quantum Batteries by Cavity Interactions

We analyse a two-cavity architecture, in which a lossy cavity hosting $N$ qubits is coherently coupled to an auxiliary cavity, as a resource for the storage phase of an open quantum battery at non-zero temperature. Within a local Lindblad treatment in the resonant configuration, we find that the inter-cavity coupling enhances the suppression of self-discharging across every initial preparation, battery size, and temperature we examine, with the protection degrading smoothly as the mean thermal occupation increases. For a single qubit, the energy-basis coherence of a pure superposition leads to better long-time retention than fully excited state, highlighting the beneficial role of quantum coherence in protecting stored energy against thermal degradation. For two-qubit batteries, Bell-state preparations exhibit enhanced long-time ergotropy retention compared with the fully excited state, while the inclusion of qubit-qubit interactions produces only a weak dependence on the interaction type and strength within the parameter regime considered. Extending the analysis to multi-qubit GHZ-charged batteries with all-to-all Heisenberg interactions, we find that the normalized retained ergotropy increases monotonically with the number of qubits. This behavior is consistent with the collective enhancement of the qubit-cavity coupling in the symmetric Dicke manifold, indicating that larger quantum batteries can benefit from improved protection against self-discharge. These findings establish cavity-assisted protection as a promising strategy for mitigating self-discharging and realizing of long-lived quantum batteries in experimentally accessible platforms.

quant-ph↗

arXiv2026

Tight Quantum Speed Limit for Ergotropy Charging in the N-Qubit Dicke Battery

We derive and analytically prove a tight quantum speed limit (QSL) for ergotropy charging in the $N$-qubit Dicke quantum battery: the first-passage time to normalised ergotropy $\epsilon$ satisfies $\tau^{*}(\epsilon) \geq \sqrt{N\epsilon}/(2\lambda\sqrt{\bar{n}})$, where $\lambda$ is the coupling and $\bar{n}$ is the mean charger photon number. The bound follows from an exact perturbative identity $\epsilon(t) = A\lambda^2\bar{n}t^2 + \mathcal{O}((\lambda t)^4)$, where $A=4/N$ is the short-time ergotropy coefficient, combined with a global upper bound proved analytically for all $N$. The composite parameter $\Gamma_N = 2\lambda\sqrt{\bar{n}/N}$ is the unique figure of merit for charging speed; all protocols collapse onto $\Gamma_N \tau^{*} \geq \sqrt{\epsilon}$, with the bound saturated to within 1% at small $\epsilon$.

quant-ph↗