Storage of energy in quantum devices is of practical relevance for applications in quantum technologies. The topic attracts attention also of a more foundational character due to the possibility that the charging power and work extraction can benefit from quantum coherence and collective effects. This Colloquium reviews theoretical concepts and experimental implementations of energy storage in quantum batteries drawing on work in quantum thermodynamics and quantum information science.
Storage of energy in quantum devices is of practical relevance for applications in quantum technologies. The topic attracts attention also of a more foundational character due to the possibility that the charging power and work extraction can benefit from quantum coherence and collective effects. This Colloquium reviews theoretical concepts and experimental implementations of energy storage in quantum batteries drawing on work in quantum thermodynamics and quantum information science.
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.
Recent advances in quantum information and quantum thermodynamics have reshaped the understanding of energy storage at the microscopic scale, paving the way toward protocols for storing and transferring energy in quantum devices. These systems, known as quantum batteries, offer a conceptual alternative to conventional macroscopic chemical batteries by exploiting quantum coherence, correlations, and many-body dynamics. By navigating the landscape of established spin-based quantum batteries, we review existing charging and work-extraction protocols, as well as the impact of external factors on their performance. Motivated by Floquet-engineered proposals, we further establish a connection between continuously and periodically driven spin chains as platforms for quantum energy storage. Finally, we survey experimental realizations and proposals, highlighting their implementability and scalability in current and near-term quantum technologies.
The progressive miniaturization of devices devoted to energy manipulation and storage calls for extending thermodynamic concepts towards regimes where quantum effects become unavoidable. In this context, quantum thermodynamics provides the proper framework for understanding and exploiting non-classical effects for energy applications. Within this framework, we present a comprehensive review of the role played by spin systems as versatile platforms for quantum energy technologies, focusing on their dual role as Quantum Thermal Machines and Quantum Batteries. We discuss how the combination of discrete spectra, engineered interactions and long coherence times enables the realization of high-performance quantum devices. We then highlight how genuinely quantum features can be exploited to achieve performance beyond classical limits. Beyond theoretical developments, we review the rapid experimental progress across leading spin platforms, including nuclear magnetic resonance systems, trapped ions, nitrogen-vacancy centers in diamond and superconducting circuits, which are bringing quantum energy devices from conceptual proposals to actual realizations. By presenting a unified spin-based framework that integrates energy conversion and storage, this review outlines the foundations of the emerging field of quantum energy and identifies key challenges and future directions for scalable quantum energy technologies.
Batteries are fundamental components of nowadays technologies and play a crucial role in our daily lives. Varying greatly in size and capacity, they are devices capable of storing energy, supplied from an external system, and releasing it in a controlled manner to a user system. Despite the impressive technological improvements over the past two centuries, the batteries we currently use still rely on the electrochemical principles exploited by A. Volta at the end of the 18th century. However, the constant miniaturization of electronic devices calls for the realization of increasingly smaller batteries, down to sizes comparable to those of molecules and atoms. At these scales, quantum effects must be taken into account. It is therefore necessary to reconsider energy manipulation within the framework of quantum thermodynamics, a research field that aims to extend the laws of classical thermodynamics and non-equilibrium statistical physics to systems where quantum effects become significant. In this context, the possibility to properly characterize the energetics of miniaturized thermal machines represented a major boost for the development of quantum technologies devoted to energy storage and manipulation. This Thesis explores solid-state quantum batteries, bridging theoretical models with experimental simulations. Key contributions include the simulation of few-level QBs on IBM quantum hardware, demonstrating the viability of superconducting circuits for energy tasks. The work introduces a cyclic QB model where quantum correlations enable efficiencies exceeding 50%, and examines a harmonic oscillator battery where non-Markovian dynamics facilitate ultra-fast charging. Finally, a novel implementation based on Graphene Josephson Junctions is proposed to realize a Dicke quantum battery. These results highlight the potential of quantum technologies for the future of miniaturized energy storage.
With intensive studies of quantum thermodynamics, quantum batteries (QBs) have been proposed to store and transfer energy via quantum effects. Despite many theoretical models, decoherence remains a severe challenge and practical platforms are still rare. Here, we propose a QB based on the coherent Ising machine, in which the signal field acts as the core energy-storage unit. To clarify the role of quantum coherence in resisting dissipation, we decompose the ergotropy, i.e., the maximum extractable work from the QB, into its coherent and incoherent components. We find that the coherent part decays at a rate roughly half that of the incoherent part, exhibiting much stronger robustness against decoherence. More importantly, the coherent ergotropy and the average charging power reach their respective maxima at essentially the same moment, which defines the optimal instant to switch off the pump field. Finally, by coupling the QB to a two-level system as the load, we demonstrate an efficient energy discharge process of the proposed QB. Our work establishes a realistic and immediately-implementable QB architecture on a mature optical platform, laying a foundation for experimental exploration of quantum energy storage.
Can collective quantum effects make a difference in a meaningful thermodynamic operation? Focusing on energy storage and batteries, we demonstrate that quantum mechanics can lead to an enhancement in the amount of work deposited per unit time, i.e., the charging power, when N batteries are charged collectively. We first derive analytic upper bounds for the collective quantum advantage in charging power for two choices of constraints on the charging Hamiltonian. We then demonstrate that even in the absence of quantum entanglement this advantage can be extensive. For our main result, we provide an upper bound to the achievable quantum advantage when the interaction order is restricted; i.e., at most k batteries are interacting. This constitutes a fundamental limit on the advantage offered by quantum technologies over their classical counterparts.