Quantum Capacitor: A Coherence-Based Quantum Energy Storage Device

Abstract

Quantum batteries have recently emerged as promising candidates for microscopic energy-storage technologies exploiting uniquely quantum mechanical effects. In this work, we introduce the concept of a quantum capacitor, a coherence-based quantum energy-storage device exhibiting reversible and ultrafast charging-discharging dynamics. Unlike conventional quantum batteries, which primarily focus on extractable work, the proposed quantum capacitor operates through reactive energy accumulation mediated by coherent quantum polarization. We formulate a theoretical framework based on a driven two-level system and define a dynamical quantum capacitance associated with the response of stored energy to coherent external driving. The charging power, reversible energy exchange, and the effects of environmental decoherence are investigated analytically within the Lindblad formalism. We extend the proposal to interacting many-body systems and show that collective coherence and interactions can enhance the effective quantum capacitance and charging power, potentially leading to cooperative energy-storage advantages beyond the single-qubit regime.