REVIEW 4 major objections 4 minor 1 cited by
Reply to the comment on "High-Power Collective Charging of a Solid-State Quantum Battery" by Haowei Xu and Ju Li
T0 review · 4 major / 4 minor · reviewed 2026-08-12 · deepseek-v4-flash
Pith's one-line read This reply concedes that the comment's two criticisms of the 2018 Dicke quantum battery are valid, but contends that both were already extensively discussed, so the comment adds no novelty to the field.
desk verdict A reply that concedes both criticisms but doesn't fully prove the comment adds nothing new. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The argument rests on two conceptual tools. First, the Dicke model after integrating out photons: the qubits experience effective all-to-all interactions mediated by photons, which is the sense in which the authors call the charging dynamics collective. Second, the thermodynamic-limit normalization distinction: fixing qubit density N/V gives a well-defined thermodynamic limit and makes the square-root-N enhancement disappear, whereas many finite laboratory systems (e.g., atoms in a cavity) operate at fixed volume with N varying up to about $10^{3}$, so the fixed-volume normalization is physically relevant and widely adopted. These mechanisms let the reply absorb the two criticisms as already-known caveats rather than new objections.
What would settle it
Identify in Xu and Li's comment (arXiv:2411.04132) any concrete quantitative claim—for example, a specific bound on the charging power, a material-dependent parameter, or a regime of N and V where the density dependence differs from the cavity models in references [3] and [4]—that is not already addressed in the cited sections of reference [15]. If such a claim exists, the 'no novelty' conclusion collapses.
Extended reading notes
Core claim
The central claim is stated directly in the opening paragraph: both criticisms raised by Xu and Li are valid, yet they have already been extensively discussed in the quantum battery literature, so the comment does not add any novelty. The reply's clarifying contribution is the distinction between quantum entanglement (not at play in the model) and collective effects (central to the model's dynamics): after integrating out the photonic degrees of freedom, the qubits interact through all-to-all photon-mediated interactions, a genuinely many-body problem that cannot be described in a single-particle fashion. The reply also defends the fixed-volume, fixed-N normalization used in the original paper as standard in circuit-QED literature and notes that the discrete square-root-N scaling of the collective dipole coupling was experimentally observed.
Load-bearing premise
The reply assumes that the cited earlier works, especially references [3], [4], and [15], fully cover every statement in Xu and Li's comment, including any nuance specific to the solid-state model in the 2018 PRL paper—but it never quotes the comment's equations or claims side-by-side to demonstrate this coverage.
Editorial extensions
If this is right
- If the reply is correct, the two criticisms in the comment should not force any correction to the 2018 PRL results; they are already covered by prior caveats in the literature.
- The community should interpret the comment as a confirmation of known limitations rather than a new finding, and direct research effort toward models with genuine quantum advantage as done in the cited later works.
- The square-root-N power scaling remains a collective, many-body effect even if a classical analog reproduces the same scaling, because the underlying dynamics involve all-to-all interactions.
- Fixed-density normalization is one valid choice for a thermodynamic limit, but it is not the only physically meaningful convention; fixed-volume normalization is supported by circuit-QED experiments.
- The reply's explicit position that the comment's criticisms are valid yet non-novel implies that future work should focus on identifying quantum advantages that are not of collective-classical origin.
Reading between the lines
- The reply asserts that earlier references cover the comment's points without ever quoting the comment's equations or claims side-by-side with the cited passages; a point-by-point mapping would make the 'no novelty' verdict inspectable.
- Because the reply concedes both criticisms as valid, the original paper's presentation of the root-N enhancement may have underemphasized these caveats; the dispute is partly about attribution and framing rather than physics.
- A testable extension: check whether the specific solid-state model in the 2018 PRL, with its own parameters and qubit-cavity coupling, exhibits any finite-size regime where the fixed-density criticism yields a quantitatively different prediction than the cavity models in the cited earlier works.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript is a short reply to a comment by Xu and Li on the authors' 2018 PRL on Dicke quantum batteries. The reply concedes that the two criticisms raised in the comment—that the square-root-of-N enhancement of the charging power is not of genuine quantum origin and that it vanishes if the qubit density is fixed—are valid, but argues that both points have already been extensively discussed in the quantum battery literature, so the comment adds no novelty. To support this, it cites prior work by the same and other authors, including a Reviews of Modern Physics Colloquium, and offers a terminological clarification of what counts as a 'collective effect.'
Significance. If the reply's coverage claim were rigorously demonstrated, it would settle a priority dispute and confirm that the comment repeats known caveats. The reply is candid in conceding both criticisms and provides useful pointers to a substantial prior literature, including a recent Colloquium treatment; that is a genuine strength. However, the central thesis of the reply—that the comment 'does not add any novelty'—is asserted rather than demonstrated: the manuscript never gives a point-by-point comparison between the comment's specific claims and the cited earlier work, and its main supporting citations are partly authored by the same researchers. Moreover, the reply's response to the comment's 'collective versus classical' point is a semantic redefinition rather than an engagement with the substance of the criticism. As a result, the reply has not convincingly established its central claim.
major comments (4)
- [First paragraph and concluding paragraph] The central claim that Ref. [1] 'does not add any novelty' is not substantiated. The reply never quotes the specific equations or statements from Xu and Li's comment, nor does it place them side-by-side with the corresponding passages in Refs. [3], [4], and [15]. Merely stating that the points 'have already been discussed at length' and citing section titles from a Colloquium is insufficient to prove full coverage, especially because the comment's claims may involve normalization conventions, thermodynamic limits, or model-specific details that the earlier works do not address in the same setting.
- [Paragraph on point i), including the quoted statement from Ref. [1]] The reply quotes Xu and Li's statement that the square-root-of-N enhancement is 'purely a classical effect, not attributable to quantum entanglement or collective phenomena' and then responds that collective effects are 'indisputable' because the dynamics are many-body with all-to-all interactions. This is an equivocation: Xu and Li use 'collective phenomena' in the sense of a collective quantum advantage, whereas the reply redefines 'collective' to mean any all-to-all or many-body dynamics. The reply therefore does not actually refute or even address the comment's claim; it changes the meaning of the term to make the disagreement look purely verbal.
- [Paragraph on point ii)] The reply admits that the square-root-of-N enhancement disappears at fixed density N/V, but argues that the normalization used in Ref. [2] is widely adopted in circuit-QED and that finite systems can have large N at fixed V. This response does not address the logical force of Xu and Li's criticism: if the original paper claimed a generic scaling enhancement of the Dicke battery without specifying that it applies only to a fixed-volume, variable-N regime, then the comment correctly identifies an unstated assumption. Citing the prevalence of a normalization is not the same as showing that the original claim was not misleading in the context in which it was presented.
- [References [3], [4], and [15] and the closing summary] The priority claim rests heavily on Refs. [3] and [15], both of which are co-authored by members of this reply's author list. While self-citation is not inherently invalid, the reply presents these works as evidence of community consensus without acknowledging that they are partly its own contributions. More importantly, the reply never shows that the specific points raised by Xu and Li are literally present in those references, leaving the reader unable to verify the 'already extensively discussed' assertion.
minor comments (4)
- [First line] There is a typographical error in 'Xu and L i' on the first line of the abstract; it should read 'Xu and Li.'
- [Paragraph following point ii)] The sentence pointing to the experiment in Ref. [8] does not explain how that experiment demonstrates that N can be varied significantly without altering cavity volume; adding a one-sentence explanation would make the argument more useful.
- [Concluding paragraph] References [13] and [14] are cited as examples of models with 'genuine quantum advantage,' but no connection is made between those examples and the two points under discussion; it would be helpful to state explicitly how these works respond to the comment's criticisms.
- [Passing comment on Ref. [15]] The statement that Ref. [15] 'thoroughly addresses issues i) and ii)' is offered without quotation or equation comparison; since the reply elsewhere relies on this reference as key evidence, providing a direct quote or paraphrase would strengthen the argument.
Circularity Check
No significant circularity: the reply's no-novelty claim is a priority argument supported by external, peer-reviewed citations, including one work by independent authors.
full rationale
This is a reply/commentary, not a derivation; there are no equations, fits, or predictions to reduce. The central claim is that Xu and Li's two criticisms are valid but already discussed in the quantum battery literature. The evidence consists of citations to Refs [3], [4], and [15] among others. Some of these are co-authored by the reply's authors, which is normal self-citation in a priority dispute. Under the hard rules, self-citation is not circular when the cited results are independent, peer-reviewed, and externally verifiable, as is the case here. Ref [4] is by an independent group, and the reply also cites experiments and other non-overlapping works. The argument does not reduce to the reply's own assertion; it points to specific prior analyses and even to a Reviews of Modern Physics review. The absence of a side-by-side quotation of the comment's equations is an evidentiary gap that could weaken the 'no novelty' conclusion, but that is a matter of completeness or correctness, not circularity. No step in the paper's argument is self-definitional, no fitted input is called a prediction, and no uniqueness theorem is imported from the authors' prior work.
Assumptions & free parameters
assumptions (2)
- domain assumption References [3], [4], and [15] accurately and completely establish that Xu and Li's two criticisms were already known before the comment, including the classical origin of the square-root enhancement and the fixed-density thermodynamic limit.
- ad hoc to paper A comment that repeats known points cannot be a significant new contribution, even if it correctly identifies a flaw in a published paper.
Cite this review
Pith. "Pith review of Reply to the comment on "High-Power Collective Charging of a Solid-State Quantum Battery" by Haowei Xu and Ju Li." pith.science (2026). https://pith.science/paper/XACRQYPC
@misc{pith2026241201830,
author = {Pith},
title = {Pith review of: Reply to the comment on "High-Power Collective Charging of a Solid-State Quantum Battery" by Haowei Xu and Ju Li},
year = {2026},
howpublished = {\url{https://pith.science/paper/XACRQYPC}},
note = {Machine review of arXiv:2412.01830}
}
read the original abstract
In this short communication we reply to the comment by Xu and Li (arXiv:2411.04132) on our first work on Dicke quantum batteries (Phys. Rev. Lett. 120, 117702 (2018)).
Forward citations
Cited by 1 Pith paper
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Molecular triplets and other metastable states for excitonic quantum batteries
Metastable dark states (triplets, fission pairs, charge-separated states) can extend excitonic quantum battery storage lifetimes by orders of magnitude, at the cost of efficiency and scalability trade-offs.
Reference graph
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Reviewed August 12, 2026 · model on record in the stance chip above.
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