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.
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.
Abstract We introduce a cyclic quantum battery QB model, based on an interacting bipartite system, weakly coupled to a thermal bath. The working cycle of the battery consists of four strokes: system thermalization, disconnection of subsystems, ergotropy extraction, and reconnection. The thermal bath acts as a charger in the thermalization stroke, while ergotropy extraction is possible because the ensuing thermal state is no longer passive after the disconnection stroke. Focusing on the case of two interacting qubits, we show that phase coherence, in the presence of non-trivial correlations between the qubits, can be exploited to reach working regimes with efficiency higher than 50% while providing finite ergotropy. Our protocol is illustrated through a simple and feasible circuit model of a cyclic superconducting QB. Furthermore, we simulate the considered cycle on superconducting IBM quantum machines. The good agreement between the theoretical and simulated results strongly suggests that our scheme for cyclic QBs can be successfully realized in superconducting quantum hardware.
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.
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.
Quantum battery, as a novel energy storage device, offers the potential for unprecedented efficiency and performance beyond the capabilities of classical systems, with broad implications for future quantum technologies. Here, we experimentally \RefC{demonstrate quantum charging advantage (QCA)} in a scalable solid-state quantum battery. More specifically, we show how double-excitation Hamiltonians for two-level systems promote scalable QCA \RefB{with standard methods.} We effectively implement the collective evolution of quantum systems with 2 up to 12 battery cells in a superconducting quantum processor, and study the performance of quantum charging compared to its uncorrelated classical counterpart. The model considered is a linear chain of superconducting transmon qubits with only \textit{nearest-neighbor} and \textit{pairwise} interactions, which constitute the simplest model of a multi-cell quantum battery. Our results empirically realize substantial QCA without the necessity of adopting long-range and many-body interactions \RefB{ and showcase the quantum features of the QB charging processes with measurements of non-zero coherent ergotropy, incoherent ergotropy and entanglement,} revealing a promising prospect for further developments of efficient and experimentally feasible protocols for QCA.
Executing quantum logic in cryogenic quantum computers requires a continuous energy supply from room-temperature control electronics. This dependence on external energy sources creates scalability limitations due to control channel density and heat dissipation. Here, we propose quantum batteries (QBs) as quantum energy sources for quantum computation, enabling the thermodynamic limit of zero dissipation for unitary gates. Unlike classical power sources, QBs maintain quantum coherence with their load—a property that, while theoretically studied, remains unexploited in practical quantum technologies. We demonstrate that initializing a bosonic QB in a Fock state can supply the energy required for arbitrary unitary gates regardless of the circuit’s depth, via the recycling of precharged energy. Crucially, allowing QB-qubit entanglement during computation lowers the QB’s initial energy requirements below established energy-fidelity bounds. This scheme facilitates a universal gate set controlled by a single parameter per qubit: its resonant frequency. The relative detuning of each qubit from the QB’s resonant frequency qualitatively gives rise to two gate types: off resonance and around resonance. The former facilitates dispersive gates that allow multiqubit parity probing while the latter enables energy exchange between the QB and the qubits, driving both population transfer and entanglement generation. This mechanism utilizes the all-to-all connectivity of the shared-resonator architecture to go beyond the standard single- and two-qubit native gates of current platforms with multiqubit gate timescales of few π / g , where g is the qubit-resonator coupling. The resultant speedup also includes superextensive gates between symmetric Dicke states, characteristic of QB systems. Using a QB eliminates the need for individual drive lines, significantly reducing wiring overhead and potentially quadrupling the number of qubits that can be integrated within cryogenic systems, thereby offering a scalable architecture for quantum computing.
We investigate the solid-state implementation of a Dicke-like quantum battery consisting of a two-dimensional material-based Josephson junction inductively coupled to a resonator, using graphene as a representative example. In this configuration, Andreev bound states naturally act as non-interacting, energetically non-degenerate two-level systems, and the setup allows for both single-photon and two-photon resonant processes. The coupling between the LC-circuit flux and the supercurrent through the junction gives rise to peculiar longitudinal interaction terms that have no counterpart in the conventional Dicke model. We demonstrate that these additional couplings can enhance energy storage for a proper range of parameters. The proposed architecture also enables an alternative, but comparable, charging protocol that relies on tuning the superconducting phase difference across the junction.