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arXiv:2607.15319

Collective Enhancement of Nuclear Excitation for a Nuclear Quantum Battery

Pravin Kumar Dahal, Kieran Hymas, Jack Muir, James Q. Quach

quant-phnucl-thSubmitted Jul 16, 2026• Announced Jul 17, 2026• 0 citations
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Abstract

Current implementations of quantum batteries are constrained by limited energy density and short retention times associated with the electronic or molecular excitations. Here we propose a nuclear quantum battery based on collective excitation of the $^{57}$Fe nuclei of density $n$ embedded in a planar hard X-ray waveguide. Using a Green function waveguide-QED description, we study charging via excitation beyond linear response, where saturation and drive back-action reshape the incident pulse. We introduce a self-consistent waveform-engineering protocol that inhibits local radiative decay in the waveguide thus promoting absorption into high-lying collective nuclear excitation manifolds. We show an enhanced excitation cross section of the nuclear ensemble which yields superlinear charging, with maximum studied energy density scaling approximately like $n \sqrt{n}$. Our results provide a route to high-energy-density quantum charging at hard X-ray energies using contemporary X-ray sources and waveguide architectures by identifying nonlinear, collectively enhanced absorption as a key mechanism for nuclear quantum battery operation.

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10 pages, 4 figures; Comments Welcome!

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Current implementations of quantum batteries are constrained by limited energy density and short retention times associated with the electronic or molecular excitations. Here we propose a nuclear quantum battery based on collective excitation of the 57^{57}57Fe nuclei of density nnn embedded in a planar hard X-ray waveguide. Using a Green function waveguide-QED description, we study charging via excitation beyond linear response, where saturation and drive back-action reshape the incident pulse. We introduce a self-consistent waveform-engineering protocol that inhibits local radiative decay in the waveguide thus promoting absorption into high-lying collective nuclear excitation manifolds. We show an enhanced excitation cross section of the nuclear ensemble which yields superlinear charging, with maximum studied energy density scaling approximately like nnn \sqrt{n}nn​. Our results provide a route to high-energy-density quantum charging at hard X-ray energies using contemporary X-ray sources and waveguide architectures by identifying nonlinear, collectively enhanced absorption as a key mechanism for nuclear quantum battery operation.
Waveguides offer a means to controllably couple atomic ensembles to the electromagnetic field therein. Here, we demonstrate x-ray propagation in planar thin-film waveguides coupled to Mössbauer nuclei under collective resonant excitation by short pulses of synchrotron radiation. We record x-ray photons that have been emitted into resonant modes of the waveguide. Depending on the geometry and mode of excitation, two fundamentally different signatures of the collective emission are observed, for which we present a unifying theoretical model. Our results form a new platform for waveguide quantum electrodynamics in the hard x-ray regime with the potential to provide a coherent narrow band source of x-rays on the nanometer scale.
Quantum batteries (QBs) -- quantum devices governed by the principles of quantum mechanics -- hold great promise for next-generation energy storage. However, most existing research efforts focus on atomic or molecular systems featuring low-energy and short-lived energy levels, leaving the exploitation of high-energy, ultra-stable nuclear energy levels for energy storage as a critical unaddressed challenge. Here, we propose an innovative design of referred to as nuclear isomer quantum batteries (NIQBs), whose energy storage unit is typically composed of two-level and three-level nuclei incorporating nuclear isomers. The charging dynamics is driven by the interaction between the nuclear system and x-ray free electron laser (XFEL). Compared to QBs based on atomic systems, NIQBs deliver substantial performance enhancements, with stored energy and average charging power enhanced by factors of 10110^{1}101--10610^{6}106 and 10610^{6}106--101110^{11}1011, respectively, and a markedly extended lifetime range spanning from microseconds to 10510^5105 years. Notably, the vast majority of NIQBs enable complete energy extraction as their excited-state lifetimes exceed the laser-nuclear interaction time, rendering spontaneous emission negligible. The proposed NIQBs framework is compatible with diverse nuclear systems, enabling tailored nucleus selection for varied operating conditions. Our results provide a feasible pathway toward realizing high-performance QBs with superior energy-storage efficiency.
Quantum batteries have demonstrated remarkable charging properties, showing that a quantum advantage is possible in the realm of quantum thermodynamics. However, finding an effective strategy to store energy for long periods remains crucial in these systems. Here, we investigate different configurations of a waveguide-QED system acting as a quantum battery and show that, in this context, collective effects can slow down the self-discharging time of the battery, thus improving the storage time. Specifically, when the artificial atoms of the array are arranged randomly, the energy and ergotropy of the optical system are shown to decay at a subexponential rate over long periods, in contrast to the energy decay of a single atom in a waveguide. In the case of atoms arranged in an ordered lattice, collective effects slow down dissipative discharging only for a specific lattice spacing. Thus, in both configurations, collective effects can be used to boost the energy-protection properties of optical systems.
In this dissertation, we investigate the charging and discharging dynamics of a quantum battery composed of a collectively driven ensemble of NNN identical two level systems coupled to a structured electromagnetic environment. The system is described using collective angular momentum operators in the Dicke basis, which provides a compact and physically transparent framework for analyzing collective light-matter interactions. Rather than treating dissipation as an unwanted source of loss, we explicitly use it as a mechanism for energy storage and work extraction. Starting from a coherently driven ensemble coupled to common reservoirs, we derive a master equation in Lindblad form under the Born-Markov and secular approximations. In the dressed-state basis, spontaneous emission induces irreversible transitions that can increase the energy stored in the bare basis. We obtain analytic expressions for the steady state, including the stored energy and the ergotropy, and identify parameter regimes where substantial collective coherence is generated. A central result of this work is the demonstration that, in the extensive regime where the total energy scales linearly with NNN and relative fluctuations vanish, the charging power scales as N2N^2N2. This quadratic enhancement scaling exceeds the N3/2N^{3/2}N3/2 limit previously established for purely Hamiltonian charging protocols of noninteracting Dicke batteries in the same regime. We show that this enhancement is consistent with quantum speed limits for open-system dynamics and originates from collectively enhanced dissipative processes analogous to superradiance. We further analyze the extraction process and show that the charged steady state stores not only energy but a macroscopic collective dipole moment. This coherence enables rapid energy release through either collective spontaneous emission or stimulated emission driven by an external coherent field. In the appropriate large NNN extensive regime, the stored energy can become fully extractable in principle, and the discharging power also exhibits N2N^2N2 scaling. These results establish that dissipative protocols can provide a genuine collective advantage over Hamiltonian schemes in the extensive regime, while also highlighting the interplay between enhanced collective power and the conditions required to achieve high extractable energy.
Thin-film nanostructures with embedded M\"ossbauer nuclei have been successfully used for x-ray quantum optical applications with hard x-rays coupling in grazing incidence. Here we address theoretically an alternative geometry, in which hard x rays are coupled in forward incidence (front coupling), setting the stage for waveguide QED with nuclear x-ray resonances. We present in a self-contained manner a general model based on the Green's function formalism of the field-nucleus interaction in one-dimensional waveguides and show that it combines aspects of both nuclear forward scattering, visible as dynamical beating in the spatiotemporal response, and the resonance structure from grazing incidence, visible in the spectrum of guided modes. The interference of multiple modes is shown to play an important role, resulting in beats with wavelengths on the order of tens of micrometers, on the scale of practical photolithography. This allows for the design of special sample geometries to explore the resonant response or microstriped waveguides, opening a toolbox of geometrical design for hard x-ray quantum optics.
Efficient operation of quantum batteries requires not only fast energy transfer but also the ability to halt the charging process to prevent reverse flow. Existing approaches typically rely on direct control of the charger-battery interaction, which can be experimentally demanding. Here we propose a modulator-assisted quantum battery protocol that enables indirect control of energy transfer while keeping the interaction always on. By applying repeated local unitary operations to an auxiliary modulator qubit, we exploit a Zeno-like mechanism to dynamically reshape the effective Hamiltonian and switch the charger-battery coupling on and off. We demonstrate this mechanism in a minimal three-body model and show that it remains effective beyond the ideal fast-control limit. We further extend the protocol to a collective many-body architecture, where it preserves the characteristic enhancement of charging power, scaling as N 3 / 2 with the number of battery units. We also discuss a possible implementation in an NV- 13 C spin platform. Our results establish modulator-assisted Zeno control as a scalable route to regulating energy transfer in quantum batteries.