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arXiv:2610.31242

Fluctuation-free Quantum Battery Charging Enabled by Bell-like Entangled and Separable Charger States

Longyan Gong, Jing Zhang, Yongtao Li

quant-phcond-mat.mes-hallSubmitted Oct 22, 2026• Announced Oct 23, 2026• 0 citations
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Abstract

The implication of entanglement in quantum battery charging remains poorly understood. In addition, intrinsic quantum randomness poses a fundamental challenge to charging uniformity across distinct trials. To address these issues, we study a three-qubit system within a cascaded collision frame, with two qubits acting as the charger and the third serving as the battery. After each collision, an adaptive measurement is performed on the charger, yielding four conditional post-measurement battery states with identical expected stored energy. For arbitrary fixed charger states, we derive analytical expressions for the recurrence relation of stored energy. We find that stored-energy fluctuations depend on whether the dynamics relies on the battery phase \(γ_n\). For two Bell-like families of entangled states, together with their computational basis states termed Bell-like separable states, the dynamics is \(γ_n\)-independent and fluctuations vanish, whereas for other entangled and separable states, fluctuations emerge. These insights establish a paradigm for engineering charger states to design uniform-charging quantum-battery architectures despite inherent quantum randomness.

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The implication of entanglement in quantum battery charging remains poorly understood. In addition, intrinsic quantum randomness poses a fundamental challenge to charging uniformity across distinct trials. To address these issues, we study a three-qubit system within a cascaded collision frame, with two qubits acting as the charger and the third serving as the battery. After each collision, an adaptive measurement is performed on the charger, yielding four conditional post-measurement battery states with identical expected stored energy. For arbitrary fixed charger states, we derive analytical expressions for the recurrence relation of stored energy. We find that stored-energy fluctuations depend on whether the dynamics relies on the battery phase (γ_n). For two Bell-like families of entangled states, together with their computational basis states termed Bell-like separable states, the dynamics is (γ_n)-independent and fluctuations vanish, whereas for other entangled and separable states, fluctuations emerge. These insights establish a paradigm for engineering charger states to design uniform-charging quantum-battery architectures despite inherent quantum randomness.
Charging uniformity across distinct trials is an essential requirement for reliable quantum batteries. Nevertheless, intrinsic quantum stochasticity poses a fundamental challenge to this goal. This work investigates a two-qubit quantum battery within the framework of cascaded collision models. We propose an adaptive measurement on the charger after each collision, yielding two conditional battery states of equal expected stored energy. For chargers prepared in the excited state, we analytically prove that complete suppression of trajectory-dependent stored-energy fluctuations is attainable; for chargers prepared in general superposition states, our theory reveals that full suppression is fundamentally prohibited owing to battery-phase-dependent recursive dynamics. Numerical simulations are in excellent quantitative agreement with theoretical predictions. These findings provide a feasible pathway toward high-uniformity quantum-battery charging.
In this work, we investigate the autonomous charging process of a quantum battery coupled to a structured reservoir composed of two qubits, each locally coupled to its own bosonic thermal bath. Moreover, the reservoir interacts with a charger-battery architecture through three configurations: (I) direct coupling between reservoir qubits and battery; (II) collective coupling among the reservoir qubits, charger, and battery; and (III) a collective coupling between the reservoir qubits and charger together with a local charger-battery interaction. However, by using incoherent and coherent initial states, we analyze the stored energy, ergotropy, and charging power of the battery, and derive upper and lower bounds on the extractable work in terms of the free energy of coherence and the correlations exchanged between subsystems. Our results show that global and local coherences, as well as total correlations, act as quantum resources that enhance autonomous charging. Additionally, we demonstrate that the free energy stored in the quantum battery splits into contributions from coherence and correlations, providing numerical evidence that supports the derived ergotropy bounds. Importantly, this work highlights how structured reservoirs enable autonomous and resource-enhanced quantum battery operation.
We propose a quantum charging scheme fueled by measurements on ancillary qubits serving as disposable chargers. A stream of identical qubits are sequentially coupled to a quantum battery of N+1N+1N+1 levels and measured by projective operations after joint unitary evolutions of optimized intervals. If charger qubits are prepared in excited state and measured on ground state, then their excitations (energy) can be near perfectly transferred to battery by iteratively updating the optimized measurement intervals. Starting from its ground state, the battery could be constantly charged to an even higher energy level. Starting from a thermal state, the battery could also achieve a near-unit ratio of ergotropy and energy through less than NNN measurements, when a population inversion is realized by measurements. If charger qubits are prepared in ground state and measured on excited state, useful work extracted by measurements alone could transform the battery from a thermal state to a high-ergotropy state before the success probability vanishes. Our operations in charging are more efficient than those without measurements and do not invoke the initial coherence in both battery and chargers. Particularly, our finding features quantum measurement in shaping nonequilibrium systems.
We provide an architecture for a multimode quantum battery based on the framework of continuous-variable systems. We examine the performance of the battery by using a generic class of multimode initial states whose parameters can be tuned to produce separable as well as entangled states and that can be charged locally as well as globally by Gaussian unitary operations. Analytical calculations show that a separable state is equally advantageous as an entangled one for two- and three-mode batteries when taking the figures of merit as the second moments of the change in energy. In order to produce a stable quantum battery consisting of an arbitrary number of modes, we derive compact analytical forms of the energy fluctuations and prove that for a multimode separable Gaussian initial state, fluctuations decrease as the number of modes increases, thereby obtaining a scaling analysis. Moreover, we demonstrate that local displacement as a charger is better for minimizing the fluctuations in energy than that involving the squeezing unitary operation.
Hamiltonian kkk-Locality is the Key Resource for Powerful Quantum Battery Charging
Storing and extracting energy using quantum degrees of freedom is a promising approach to leveraging quantum effects in energy science. Early experimental efforts have already demonstrated its potential to surpass the charging power of existing technologies. In this context, it is crucial to identify the specific quantum effects that can be exploited to design the most efficient quantum batteries and push their performance to the ultimate limit. While entanglement has often been considered a key factor in enhancing charging (or discharging) power, our findings reveal that it is not as critical as previously thought. Instead, three parameters emerge as the most significant in determining the upper bound of instantaneous charging power: the locality of the battery and charger Hamiltonians, and the maximum energy storable in a single unit cell of the battery. To derive this new bound, we have also addressed several open questions previously noted in the literature but lacks an explanation. This bound provides a foundation for designing the most powerful charger-battery systems, where combined optimization of both components offers enhancements that cannot be achieved by manipulating only one of them.
Energy can be stored in quantum batteries by electromagnetic fields as chargers. In this paper, the performance of a quantum battery with single and double chargers is studied. It is shown that by using two independent charging fields, prepared in coherent states, the charging power of the quantum battery can be significantly improved, though the average number of embedded photons are kept the same in both scenarios. The results reveal that for the case of initially correlated states of the chargers, the amount of extractable energy, measured by ergotropy, is more than initially uncorrelated ones, with appropriate degrees of field intensity. Though the correlated chargers lead to greater reduction in the purity of the quantum battery, more energy and in turn more ergotropy are stored in this case. In addition, we study the battery-charger mutual information and von Neumann entropy and by using their relation we find that both quantum and classical correlations are generated between the quantum battery and chargers. We also study quantum consonance of the battery as the nonlocal coherence among its cells and find some qualitative relations between the generation of such correlations and the capability of energy storage in the quantum battery.