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arXiv:2607.16645 · Physical Review A

Geometric power capacity of coherent ergotropy in quantum batteries

Dong-Ping Xuan, Hua Nan, Zhi-Xi Wang, Shao-Ming Fei

quant-phSubmitted Jul 18, 2026• Announced Jul 21, 2026• 0 citations• Revised Oct 17, 2026 (v3)
v1 · Jul 18, 2026v2 · Jul 23, 2026v3 · Oct 17, 2026
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Abstract

We explore coherent ergotropy extraction in quantum batteries from a resource-geometric point of view. For an initial state $ρ$, we quantify the coherent extraction process by the coherent ergotropy $\mathcal{E}_c(ρ)$ and the coherent extraction distance $D_c^{\rm ext}(ρ)$ between the active state $σ_ρ$ and the passive state $P_ρ$. This defines the geometric power capacity $Π_c(ρ)=\mathcal{E}_c(ρ)/D_c^{\rm ext}(ρ)$, which measures the coherent ergotropy released unit minimal unitary distance. We prove that, for any driving Hamiltonian satisfying $\|V_t\|\leqν$, the actual coherent discharging power is bounded by $P_c^{\rm ext}(ρ;V_t)\leq νΠ_c(ρ)$, showing that $Π_c(ρ)$ is a capacity under unit driving norm rather than the power of a particular protocol. General bounds on $Π_c(ρ)$ are derived by combining relative entropy bounds on coherent ergotropy with geometric bounds on the coherent extraction distance. We also formulate coherence measure induced bounds and protocol-corrected capacities involving the effective speed of a given Hamiltonian. Qubit and qutrit examples demonstrate that $Π_c(ρ)$ captures a resource-geometric feature of coherent discharging beyond coherent ergotropy or coherence measures alone.

Journal reference
Phys. Rev. A 114, 042211 Published 15 October, 2026
DOI
10.1103/37q3-92p9
Comments
18 pages, 9 figure

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