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arxiv: 2605.07449 · v1 · submitted 2026-05-08 · 🪐 quant-ph

Hybrid Qubit-Qutrit Quantum Battery: Nonclassicality and Energy Performance

G. Sharvan Prakash , R. Muthuganesan This is my paper

Pith reviewed 2026-05-11 02:20 UTC · model grok-4.3

classification 🪐 quant-ph
keywords quantum batteryqubit-qutrit hybridquantum coherenceentanglementergotropyHeisenberg couplingnickel-radical complexroom temperature
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The pith

A hybrid qubit-qutrit system functions as a quantum battery whose performance is boosted by coherence and realizable at room temperature in a nickel-radical complex.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper sets out to show that a mixed spin-1/2 and spin-1 system coupled by anisotropic Heisenberg exchange in a magnetic field can operate as a quantum battery. It quantifies how coherence and entanglement improve ergotropy and power while capacity stays fixed, then links the model to an actual nickel-radical molecule. A reader would care because the connection implies that the quantum advantages survive without cryogenic cooling, offering a concrete molecular route to usable quantum energy storage.

Core claim

We propose and analyze a hybrid qubit-qutrit quantum battery based on a mixed spin-1/2 and spin-1 system interacting via anisotropic Heisenberg exchange coupling in a homogeneous magnetic field. The l1-norm of coherence and negativity characterize the nonclassical properties, while ergotropy, power, and capacity evaluate battery performance. Both ergotropy and power exhibit oscillatory dynamics, capacity remains constant, and nonclassicality enhances energy-storage efficiency. The theoretical model connects to an experimentally realizable nickel-radical molecular complex in which quantum coherence, entanglement, and efficient storage persist at room temperature.

What carries the argument

The anisotropic Heisenberg exchange coupling between the spin-1/2 qubit and spin-1 qutrit in a magnetic field, which generates the coherence and entanglement that drive the observed battery metrics.

If this is right

  • Ergotropy and power oscillate in time while capacity stays constant.
  • Higher values of coherence and negativity produce larger ergotropy and power.
  • The battery metrics remain usable when the model parameters match those of the nickel-radical complex at room temperature.
  • Nonclassical correlations are required for the efficiency gains reported in the hybrid system.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • Similar spin-1/2 spin-1 molecular platforms could be screened for still higher room-temperature ergotropy by varying ligand fields.
  • If the oscillatory power can be phase-locked to an external load, the hybrid system might supply pulsed energy on demand without additional control qubits.
  • Room-temperature operation removes the need for dilution refrigerators, potentially allowing quantum batteries to be tested in standard chemistry labs using existing molecular magnets.

Load-bearing premise

The chosen values for the anisotropic coupling strength and magnetic field must accurately describe the real nickel-radical complex at room temperature with no significant extra decoherence or unmodeled interactions.

What would settle it

Direct measurement of ergotropy oscillations or coherence in the nickel-radical complex at room temperature that shows no enhancement over a classical counterpart or rapid loss of the predicted correlations would disprove the practical claim.

Figures

Figures reproduced from arXiv: 2605.07449 by G. Sharvan Prakash, R. Muthuganesan.

Figure 1
Figure 1. Figure 1: FIG. 1. Schematic representation of Quantum battery in Qubit-Qutrit system [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. Temporal evolution of (a) [PITH_FULL_IMAGE:figures/full_fig_p006_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. Temporal evolution of (a) ergotropy, (b) power and (c) capacity of hybrid quantum battery as a function of time at a [PITH_FULL_IMAGE:figures/full_fig_p006_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. Temporal evolution of (a) [PITH_FULL_IMAGE:figures/full_fig_p007_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5. Temporal evolution of (a) ergotropy, (b) power and (c) capacity as a function of time at a few selected values of [PITH_FULL_IMAGE:figures/full_fig_p007_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: FIG. 6. Temporal evolution of (a) [PITH_FULL_IMAGE:figures/full_fig_p008_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: FIG. 7. Temporal evolution of (a) ergotropy, (b) power and (c) capacity of the hybrid quantum battery as a function of time [PITH_FULL_IMAGE:figures/full_fig_p009_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: FIG. 8. (a) Temporal evolution of quantumness measures such as [PITH_FULL_IMAGE:figures/full_fig_p009_8.png] view at source ↗
Figure 9
Figure 9. Figure 9: FIG. 9. (a) Temporal evolution of quantumness measures such as [PITH_FULL_IMAGE:figures/full_fig_p010_9.png] view at source ↗
read the original abstract

We propose and analyze a hybrid qubit-qutrit quantum battery (QB) based on a mixed spin-1/2 and spin-1 system interacting via an anisotropic Heisenberg exchange coupling in the presence of a homogeneous magnetic field. The nonclassical properties of the system are characterized using the l1-norm of coherence and negativity, which quantify quantum coherence and entanglement, respectively. The performance of the quantum battery is evaluated through key indicators such as ergotropy, power, and capacity. Our results reveal that both ergotropy and power exhibit oscillatory dynamics, while the capacity remains constant over time. We further investigate the influence of system parameters and magnetic field strength on both quantum correlations and battery performance, demonstrating that nonclassicality plays a crucial role in enhancing energy-storage efficiency. Importantly, we establish a connection between the theoretical model and an experimentally realizable nickel-radical molecular complex, showing that quantum coherence, entanglement, and efficient energy storage persist even at room temperature. These findings provide a realistic pathway toward the implementation of hybrid qubit-qutrit quantum batteries in solid-state molecular platforms.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The paper proposes a hybrid qubit-qutrit quantum battery consisting of a mixed spin-1/2 and spin-1 system coupled by anisotropic Heisenberg exchange in a homogeneous magnetic field. Nonclassicality is quantified via the l1-norm of coherence and negativity; battery performance is evaluated via ergotropy, power, and capacity, which exhibit oscillatory dynamics in the first two quantities and constant capacity. The model is mapped to an experimentally reported nickel-radical molecular complex, with the central claim that coherence, entanglement, and efficient storage persist at room temperature.

Significance. If the room-temperature claim can be substantiated, the work would supply a concrete molecular platform linking quantum correlations to battery metrics and offering a realistic route toward solid-state quantum batteries. The use of standard, independently defined quantifiers (l1-coherence, negativity, ergotropy) and the explicit parameter mapping to a known complex are positive features.

major comments (2)
  1. [Abstract and nickel-radical mapping section] Abstract and the section linking the model to the nickel-radical complex: the assertion that 'quantum coherence, entanglement, and efficient energy storage persist even at room temperature' is based exclusively on closed-system unitary evolution of the time-independent anisotropic Heisenberg Hamiltonian. No Lindblad operators, master-equation terms, or estimates of spin-phonon relaxation rates (T2 ~ ns–μs) are provided, even though kT at 300 K greatly exceeds the reported exchange and anisotropy scales; this omission directly undermines the persistence of the reported oscillations.
  2. [Model section] Model Hamiltonian and parameter choice: the values of J, D, and B are taken from experimental literature on the Ni-radical complex, yet the manuscript provides no quantitative argument that these parameters remain valid once thermal relaxation channels are included, nor any comparison of the unitary oscillation period to expected decoherence times.
minor comments (2)
  1. [Nonclassicality section] Notation for the qubit-qutrit basis states and the explicit form of the l1-coherence and negativity expressions should be stated once in a dedicated subsection for clarity.
  2. [Results figures] Figure captions for the time-dependent plots of ergotropy and power should include the specific parameter values (J, D, B, temperature) used in each panel.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful and constructive report. The major comments correctly highlight that our analysis is restricted to closed-system unitary evolution and that the room-temperature persistence claim therefore requires qualification. We address each point below and will revise the manuscript to incorporate appropriate caveats and additional discussion.

read point-by-point responses

  1. Referee: [Abstract and nickel-radical mapping section] Abstract and the section linking the model to the nickel-radical complex: the assertion that 'quantum coherence, entanglement, and efficient energy storage persist even at room temperature' is based exclusively on closed-system unitary evolution of the time-independent anisotropic Heisenberg Hamiltonian. No Lindblad operators, master-equation terms, or estimates of spin-phonon relaxation rates (T2 ~ ns–μs) are provided, even though kT at 300 K greatly exceeds the reported exchange and anisotropy scales; this omission directly undermines the persistence of the reported oscillations.

    Authors: We agree that the current claim is overstated. Our study examines only the closed-system dynamics generated by the time-independent anisotropic Heisenberg Hamiltonian, and the nickel-radical complex is invoked solely because its reported parameters (J, D, B) match the model and the complex itself has been synthesized at room temperature. We will revise the abstract and the mapping section to state that the unitary evolution demonstrates the potential for sustained nonclassicality and constant capacity under ideal conditions. We will add a dedicated paragraph noting that thermal relaxation and decoherence (with typical T2 on the ns–μs scale) are expected to damp the oscillations and that a full open-system treatment lies beyond the present scope. The revised text will avoid any implication that the reported oscillations persist at room temperature without further analysis. revision: yes

  2. Referee: [Model section] Model Hamiltonian and parameter choice: the values of J, D, and B are taken from experimental literature on the Ni-radical complex, yet the manuscript provides no quantitative argument that these parameters remain valid once thermal relaxation channels are included, nor any comparison of the unitary oscillation period to expected decoherence times.

    Authors: We acknowledge the absence of such a comparison. The parameter values are taken directly from the experimental literature on the nickel-radical complex to anchor the model in a realizable system. In the revised manuscript we will insert a quantitative discussion that (i) extracts the characteristic oscillation period of the ergotropy from the energy eigenvalues of the Hamiltonian and (ii) contrasts this period with literature values of decoherence times for analogous molecular spin systems. We will explicitly note that the quoted parameters describe the coherent regime and that their validity under strong thermal relaxation would require an open-system treatment, which we flag as future work. This addition will supply the requested argument while preserving the closed-system focus of the present study. revision: yes

Circularity Check

0 steps flagged

No circularity: standard QI measures on literature-parameterized Hamiltonian

full rationale

The derivation begins with an anisotropic Heisenberg Hamiltonian whose parameters (J, D, B) are taken directly from external experimental reports on the nickel-radical complex. It then applies the independently defined l1-norm of coherence, negativity, and ergotropy to the unitary time evolution generated by that Hamiltonian. None of these quantities are fitted to the target performance metrics, nor are any results obtained by renaming or self-referential definition of the inputs. The room-temperature persistence statement follows from plugging the literature values into the closed-system dynamics; while this modeling choice may be critiqued on physical grounds, it does not constitute a circular reduction of the claimed results to the paper's own definitions or fitted parameters.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Only the abstract is available, so free parameters, axioms, and invented entities cannot be enumerated in detail. The work relies on standard quantum mechanics and open-system dynamics without introducing new postulated entities.

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Reference graph

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