REVIEW 3 major objections 4 minor 55 references
Tuning the coupling range in a random quantum hopping model reveals an intermediate localized regime, attributed to structural disorder.
Reviewed by Pith at T0; open to challenge. T0 means a machine referee read the full paper against a public rubric. the ladder, T0–T4 →
T0 review · deepseek-v4-flash
2026-08-01 21:05 UTC pith:FTN5KKHT
load-bearing objection The single-particle intermediate-range localization looks real and worth engaging; the finite-density claim rests on a free-fermion surrogate that is not the model in Eq. (3). the 3 major comments →
Entanglement Entropy in Quantum Networks with Tunable Geometry
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Central claim: the random graph with link probability c|j−ℓ|^{−α} and c=1 shows an intermediate localized regime between the chain (α→∞) and all-to-all (α→0) limits. The asymptotic entanglement entropy S∞ is non-monotonic in α, dropping to a minimum at intermediate α, as corroborated by the inverse participation ratio. This is attributed to structural disorder: random long-range links act as scattering impurities, and a large-α impurity model fits S∞(α). The effect also appears at half-filling, with S∞/(N log 2) reaching about 0.28 for delocalized regimes, consistent with a random Gaussian state—but the finite-density calculation uses a free-fermion Hamiltonian obtained by deleting the strin
What carries the argument
The key object is the random graph ensemble defined by independent link probability c|j−ℓ|^{−α}, with c=1 for the main results. The quantum dynamics is the hopping Hamiltonian H=J∑ A_{jℓ} σ_j^+ σ_ℓ^- (hard-core bosons), and the central diagnostic is the asymptotic entanglement entropy S∞ of a spatial bipartition, complemented by the inverse participation ratio. The explanatory mechanism is a large-α approximation in which the graph is viewed as a one-dimensional chain (nearest-neighbor links) with rare length-2 links acting as scattering impurities; treating the wavefunction as exponentially localized with decay length λ set by the impurity density 2^{-α} yields a fit to S∞(α). This impurity
Load-bearing premise
The finite-density claim rests on replacing the hard-core bosons by spinless fermions and deleting the string terms of a Jordan–Wigner transformation, an operation the paper admits changes the Hamiltonian except in the single-particle sector.
What would settle it
Run exact diagonalization of the hard-core boson Hamiltonian at half-filling for N up to about 20 and see whether the intermediate-α dip in S∞/(N log 2) survives; if the dip vanishes or shifts, the finite-density claim is not supported. Alternatively, measure the single-particle inverse participation ratio for N=200,400,800 at α≈3: a true localized phase has IPR saturating to a constant, while a finite-size crossover would show IPR decreasing with N.
If this is right
- The intermediate-α localized regime persists at half-filling (in the free-fermion surrogate), so the effect is not an artifact of the single-particle sector.
- The localized wavefunction's decay length depends only on α, not on system size N, so larger systems exhibit smaller S∞ and a clearer localized signal.
- The localization is caused by off-diagonal (structural) disorder in the coupling pattern, not by on-site noise or by the classical percolation transition.
- The model offers a concrete mechanism for Anderson localization in amorphous materials and for experiments with tunable-range Rydberg or dipolar simulators.
Where Pith is reading between the lines
- A direct test of the hard-core boson model at half-filling (e.g., small-system exact diagonalization) is needed, since the paper's finite-density results come from an inequivalent free-fermion Hamiltonian.
- If the structural-disorder mechanism is the cause, the same intermediate localization should appear in observables like mean-squared displacement or conductivity, which the paper does not compute.
- The impurity model predicts a localization length scaling as 1/λ ∝ 2^{-α}; fitting the exponential tail of the single-particle wavefunction directly would provide a sharper test than the entropy.
- On graphs with different degree distributions, a similar non-monotonic entropy could serve as a signature of non-ergodic, multifractal phases—an extension the paper mentions as future work.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper studies quantum hopping on a random graph model with link probability c |j-l|^{-alpha}, interpolating between all-to-all (alpha=0) and one-dimensional chain (alpha->infinity) geometries. For c=1, exact-diagonalization simulations of the single-particle sector and Gaussian-state simulations of the half-filled sector are used to compute asymptotic entanglement entropy, IPR, and wavefunction spreading. The central claim is that, as alpha is varied, the system exhibits an unexpected intermediate localized regime caused by structural disorder, and that this regime is robust in both single-particle and finite-density cases. A large-alpha approximate model treats length-2 links as impurities and fits a single parameter to reproduce the decreasing entropy.
Significance. If the result holds, the paper identifies a genuinely interesting mechanism: Anderson-like localization produced by randomness in the connectivity pattern of a graph, without on-site disorder. The single-particle numerical evidence is internally cross-checked: it uses sample-averaged data with error bars, two bipartitions, IPR corroboration, and an N-dependence consistent with a localized wavefunction. This part is a useful contribution. However, the finite-density leg of the claim is computed in a free-fermion model obtained by deleting Jordan-Wigner strings from the hard-core boson Hamiltonian, a model the authors themselves state is inequivalent to Eq. (3). As a result, the abstract's 'robust in both single-particle and finite-density cases' is not established by the reported numerics. The explanatory large-alpha model is also fit to the same data it explains, and no scaling collapse is provided to justify the thermodynamic-limit language. These gaps are load-bearing and require revision before the central claim can be accepted.
major comments (3)
- [Methods, 'Half-filling case'; Fig. 3; Figs. S5/S6] The finite-density results are obtained by replacing hard-core bosons in Eq. (3) with spinless fermions and 'deleting the Jordan-Wigner strings.' The manuscript explicitly states that this Hamiltonian 'is not equivalent to the previous one, except for the single-particle sector.' On generic non-path graphs, the omitted string operators do not cancel, so the simulated model is a different noninteracting theory. All half-filling claims, including S_inf/(N log 2) ~ 0.28 and the comparison to random Gaussian states, are therefore not evidence about the hard-core boson model of Eq. (3). The abstract and conclusions nevertheless present the localized regime as 'robust in both single-particle and finite-density cases.' This is an internal-consistency gap. The authors should either simulate the actual hard-core boson model at finite density (e.g., small-N ED, tensor networks, or other controlled
- [Supplemental Material, 'Large-alpha limit at c=1'; Fig. S7; Fig. 3] The large-alpha 'prediction' for S_inf(alpha) is a one-parameter least-squares fit of A in 1/lambda = 2^{-alpha} A against the same numerical data it is intended to explain. Moreover, the fitted A drifts with system size (0.36, 0.292, 0.233, 0.206 for increasing N), so the model is not a parameter-free predictive derivation. More importantly, the thermodynamic-limit statement is based only on the qualitative trend that S_inf decreases with N; no finite-size scaling collapse is presented, so this could be a finite-size crossover rather than a true localized phase. For the central 'new localization regime' claim, the authors should provide a scaling analysis or otherwise specify the regime of validity of the extrapolation.
- [Results, Case c=1, first paragraph] The text states that the alpha=0 limit is the 'all-to-all model, fully localized as N->infinity.' For a single particle on a complete graph with an initially localized state, the long-time state is delocalized and the asymptotic entanglement entropy is maximal, not zero. This statement is also inconsistent with the same paragraph's assertion that 'reaches maximally entangled values for alpha <= 2' and with Fig. 4a, where the probability spreading is 'almost uniform on all sites' at small alpha. This appears to be a typographical error, but as written it misstates a benchmark and should be corrected.
minor comments (4)
- [Fig. 3 and text below it] The half-filling curve is said to saturate at S_inf/(N log 2) ~ 0.28, which is consistent with S/N -> log 2 - 1/2 after normalization. This conversion is not explained in the main text; please define the normalization explicitly in the figure caption or text.
- [Supplemental Material, 'Results with c<1', Fig. S4] The dotted reference line in Fig. S4 is described as 'the fraction of sites in the cluster' computed at the largest N. Please state in the caption which N is used and whether the comparison across N is affected by this choice.
- [Methods, Eq. (3)] The notation [b_j, b_l^dagger] = delta_{jl}(I - 2 n_j) is the anti-commutator-like relation for hard-core bosons on the same site and a commutator on different sites. It would help to state explicitly that this is the standard hard-core boson algebra, as the mixed commutator/anti-commutator form can confuse readers.
- [Supplemental Material, 'Kac normalization'] The Kac normalization discussion is clear but would benefit from a statement of whether the main-text results are Kac-normalized. The sentence 'the results remain unaffected' at alpha>1 should be made more precise by specifying that time is rescaled and S_inf is unchanged.
Circularity Check
The large-α explanation of the localized regime is a one-parameter fit to the data it is said to predict; the central numerical result and IPR remain independent, while the finite-density leg uses an inequivalent free-fermion surrogate.
specific steps
-
fitted input called prediction
[Results, 'Case c=1' paragraph; Supplemental Material, 'Large-α limit at c=1', Fig. S7]
"From it, we obtain a localized wavefunction (see Supplemental Material for the details) and derive a prediction for S∞(α) that has been fit to the actual numerical data, with good agreement for large values of α (see Fig. S7). ... We perform a least-squares fit with A as only parameter (see Fig. S7). ... the best-fit values of A are (with increasing N) 0.36, 0.292, 0.233, 0.206."
The 'prediction' for S∞(α) in the large-α Anderson-impurity model has one free parameter, the single-impurity absorption amplitude A in 1/λ = 2^{−α}A. A is determined by least-squares fitting to the very S∞(α) curves (Fig. 3 / Fig. S7) that the model is then said to predict. Thus the agreement in Fig. S7 is not an independent check: it demonstrates only that the chosen exponential ansatz can be matched to the tail once A is fitted. The core non-monotonic/intermediate-localization claim does not rest on this fit (the authors note it fails for α<2), but the 'prediction' label overstates what the fit establishes.
full rationale
The central single-particle result—non-monotonic S∞(α) with an intermediate localized regime—is obtained by exact diagonalization of the original Hamiltonian (3), with no fitted parameters, cross-checked by the IPR and by the known α=0 and α→∞ benchmarks. That part of the derivation is self-contained and does not reduce to its inputs. The only identifiable circular step is the large-α 'prediction' from the disordered-chain model: the decay-length amplitude A is fitted to the same numerical S∞ data the model is used to explain, so the agreement is a fitted post-hoc explanation rather than a parameter-free prediction. This step is supporting, not load-bearing for the main claim. Separately, the half-filling results are computed for spinless fermions obtained by 'deleting the Jordan–Wigner strings', a Hamiltonian the paper explicitly states 'is not equivalent to the previous one, except for the single-particle sector'; this is a model-validity gap for the abstract's 'robust in both single-particle and finite-density cases' claim, but it is not circularity. No load-bearing self-citation chain or imported uniqueness theorem was found.
Axiom & Free-Parameter Ledger
free parameters (1)
- A (single-impurity scattering amplitude in the large-α model) =
0.36, 0.292, 0.233, 0.206 (for increasing N)
axioms (5)
- domain assumption Graph model of Eq. (1): link probability c|j−ℓ|^{−α}, with the classical percolation phase diagram (α∈(1,2) transition)
- domain assumption One-dimensional disordered quantum systems localize, with exponentially decaying wavefunction amplitude (Anderson localization)
- ad hoc to paper Deleting Jordan–Wigner strings yields a physically informative finite-density model
- ad hoc to paper Links of length r>2 can be neglected in the large-α limit
- domain assumption Saturation of dynamics by t = 10^4 ℏ/J uniformly across parameters
read the original abstract
Quantum many-body Hamiltonians with two-body interactions can be represented by graphs, with sites as nodes and two-site couplings as edges. We investigate how the geometry of these graphs affects transport and entanglement growth. To do so, we study dynamics for quantum hopping on a random graph model with an effective range parameter. Tuning it, we interpolate between nearest-neighbor and all-to-all graphs, identifying a new localization regime that is robust in both single-particle and finite-density cases. This provides a model of Anderson localization induced by structural disorder, with implications for amorphous materials and tunable-range analog quantum simulators.
Figures
Reference graph
Works this paper leans on
-
[1]
M. K. Joshi, A. Elben, B. Vermersch, T. Brydges, C. Maier, P. Zoller, R. Blatt, and C. F. Roos, Physical Review Letters124, 240505 (2020)
2020
-
[2]
B. Yan, S. A. Moses, B. Gadway, J. P. Covey, K. R. A. Hazzard, A. M. Rey, D. S. Jin, and J. Ye, Nature501, 521 (2013)
2013
-
[3]
Baier, M
S. Baier, M. J. Mark, D. Petter, K. Aikawa, L. Chomaz, Z. Cai, M. Baranov, P. Zoller, and F. Ferlaino, Science 352, 201 (2016)
2016
-
[4]
A. S. Buyskikh, M. Fagotti, J. Schachenmayer, F. Essler, and A. J. Daley, Physical Review A93, 053620 (2016), arXiv:1601.02106 [cond-mat]
Pith/arXiv arXiv 2016
-
[5]
Defenu, T
N. Defenu, T. Donner, T. Macr ` ı, G. Pagano, S. Ruffo, and A. Trombettoni, Reviews of Modern Physics95, 035002 (2023)
2023
-
[6]
Defenu, A
N. Defenu, A. Lerose, and S. Pappalardi, Physics Reports 1074, 1 (2024)
2024
-
[7]
G. Bentsen, Y. Gu, and A. Lucas, Proceedings of the National Academy of Sciences116, 6689 (2019), arXiv:1805.08215 [cond-mat]
Pith/arXiv arXiv 2019
-
[8]
Bentsen, T
G. Bentsen, T. Hashizume, A. S. Buyskikh, E. J. Davis, A. J. Daley, S. S. Gubser, and M. Schleier-Smith, Physi- cal Review Letters123, 130601 (2019)
2019
-
[9]
Hashizume, S
T. Hashizume, S. Kuriyattil, A. J. Daley, and G. Bentsen, Symmetry14, 666 (2022)
2022
-
[10]
Kuriyattil, T
S. Kuriyattil, T. Hashizume, G. Bentsen, and A. J. Daley, PRX Quantum4, 030325 (2023)
2023
-
[11]
Hashizume, G
T. Hashizume, G. S. Bentsen, S. Weber, and A. J. Daley, Physical Review Letters126, 200603 (2021)
2021
-
[12]
Bluvstein, S
D. Bluvstein, S. J. Evered, A. A. Geim, S. H. Li, H. Zhou, T. Manovitz, S. Ebadi, M. Cain, M. Kalinowski, D. Hangleiter, J. P. Bonilla Ataides, N. Maskara, I. Cong, X. Gao, P. Sales Rodriguez, T. Karolyshyn, G. Semegh- ini, M. J. Gullans, M. Greiner, V. Vuleti´ c, and M. D. Lukin, Nature626, 58 (2024)
2024
-
[13]
M. A. Valdez, D. Jaschke, D. L. Vargas, and L. D. Carr, Physical Review Letters119, 225301 (2017)
2017
-
[14]
Nokkala, F
J. Nokkala, F. Arzani, F. Galve, R. Zambrini, S. Manis- calco, J. Piilo, N. Treps, and V. Parigi, New Journal of Physics20, 053024 (2018)
2018
-
[15]
J. Nokkala, J. Piilo, and G. Bianconi, Journal of Physics A: Mathematical and Theoretical57, 233001 (2024), arXiv:2311.16265 [quant-ph]
Pith/arXiv arXiv 2024
-
[16]
D. S. Bhakuni, R. Verdel, C. Muzzi, R. Andreoni, M. Aidelsburger, and M. Dalmonte, Physical Review B 110, 144204 (2024)
2024
-
[17]
Ausilio, F
S. Ausilio, F. Borgonovi, G. L. Celardo, J. Yago Malo, and M. L. Chiofalo, Physical Review B113, 064201 (2026)
2026
-
[18]
De Luca, B
A. De Luca, B. Altshuler, V. Kravtsov, and A. Scardic- chio, Physical Review Letters113, 046806 (2014)
2014
-
[19]
Sierant, M
P. Sierant, M. Lewenstein, and A. Scardicchio, SciPost Physics15, 045 (2023)
2023
-
[20]
L. F. Cugliandolo, G. Schehr, M. Tarzia, and D. Ven- turelli, Physical Review B110, 174202 (2024)
2024
-
[21]
Bhattacharjee, P
S. Bhattacharjee, P. Sierant, M. Dudy´ nski, J. Wehr, J. Zakrzewski, and M. Lewenstein, Physical Review B 111, L180202 (2025)
2025
-
[22]
Tikhonov and A
K. Tikhonov and A. Mirlin, Annals of Physics435, 168525 (2021)
2021
-
[23]
Lunkinet al., Hilbert space signatures of non-ergodic glassy dynamics (2026), arXiv:2601.01309
A. Lunkinet al., Hilbert space signatures of non-ergodic glassy dynamics (2026), arXiv:2601.01309
Pith/arXiv arXiv 2026
-
[24]
C.-T. Toh, H. Zhang, J. Lin, A. S. Mayorov, Y.-P. Wang, C. M. Orofeo, D. B. Ferry, H. Andersen, N. Kakenov, Z. Guo, I. H. Abidi, H. Sims, K. Suenaga, S. T. Pan- telides, and B. ¨Ozyilmaz, Nature577, 199 (2020)
2020
-
[25]
H. Tian, Y. Ma, Z. Li, M. Cheng, S. Ning, E. Han, M. Xu, P.-F. Zhang, K. Zhao, R. Liet al., Nature615, 56 (2023)
2023
-
[26]
Fujii and K
K. Fujii and K. Nakajima, Physical Review Applied8, 024030 (2017)
2017
-
[27]
Mujal, R
P. Mujal, R. Mart ´ ınez-Pe˜ na, J. Nokkala, J. Garc ´ ıa-Beni, G. L. Giorgi, M. C. Soriano, and R. Zambrini, Advanced Quantum Technologies4, 2100027 (2021)
2021
-
[28]
A. D. Mirlin and Y. V. Fyodorov, Nuclear Physics B366, 507 (1991)
1991
-
[29]
Baroni, G
M. Baroni, G. G. Lorenzana, T. Rizzo, and M. Tarzia, Physical Review B109, 174216 (2024)
2024
-
[30]
Kirkpatrick and T
S. Kirkpatrick and T. P. Eggarter, Physical Review B6, 3598 (1972)
1972
-
[31]
Schubert and H
G. Schubert and H. Fehske (Springer Berlin Heidelberg, Berlin, Heidelberg, 2009) pp. 1–28, in Quantum and Semi-classical Percolation and Breakdown in Disordered Solids
2009
-
[32]
A. D. Mirlin, Y. V. Fyodorov, A. Mildenberger, and F. Evers, Physical Review Letters97, 046803 (2006)
2006
-
[33]
Aizenman and C
M. Aizenman and C. M. Newman, Communications in Mathematical Physics107, 611 (1986)
1986
-
[34]
Leuzzi, G
L. Leuzzi, G. Parisi, F. Ricci-Tersenghi, and J. J. Ruiz- Lorenzo, Physical Review Letters101, 107203 (2008). 6
2008
-
[35]
E. Brezin, G. Parisi, and F. Ricci-Tersenghi, Journal of Statistical Physics157, 855 (2014), arXiv:1407.3358 [cond-mat]
Pith/arXiv arXiv 2014
-
[36]
G. Gori, M. Michelangeli, N. Defenu, and A. Trombet- toni, Physical Review E96, 012108 (2017), publisher: American Physical Society
2017
-
[37]
A. P. Mill´ an, G. Gori, F. Battiston, T. Enss, and N. Defenu, Physical Review Research3, 023015 (2021), arXiv:2006.10421 [cond-mat]
Pith/arXiv arXiv 2021
-
[38]
Peschel, Journal of Physics A: Mathematical and Gen- eral36, L205 (2003)
I. Peschel, Journal of Physics A: Mathematical and Gen- eral36, L205 (2003)
2003
-
[39]
Surace and L
J. Surace and L. Tagliacozzo, SciPost Physics Lecture Notes , 54 (2022)
2022
-
[40]
P. W. Anderson, Physical Review109, 1492 (1958)
1958
-
[41]
Landauer, Philosophical Magazine21, 863 (1970)
R. Landauer, Philosophical Magazine21, 863 (1970)
1970
-
[42]
P. W. Anderson, D. J. Thouless, E. Abrahams, and D. S. Fisher, Physical Review B22, 3519 (1980)
1980
-
[43]
Bianchi, L
E. Bianchi, L. Hackl, and M. Kieburg, Physical Review B103, L241118 (2021)
2021
-
[44]
H. P. L¨ uschen, P. Bordia, S. S. Hodgman, M. Schreiber, S. Sarkar, A. J. Daley, M. H. Fischer, E. Altman, I. Bloch, and U. Schneider, Physical Review X7, 011034 (2017)
2017
-
[45]
Stanzione, A
V. Stanzione, A. Civolani, J. Y. Malo, and M. L. Chio- falo, Physical Review B112, 224209 (2025)
2025
-
[46]
Hatano and D
N. Hatano and D. R. Nelson, Physical Review Letters 77, 570 (1996)
1996
-
[47]
Hatano and D
N. Hatano and D. R. Nelson, Physical Review B56, 8651 (1997)
1997
-
[48]
M. S. Rudner and L. S. Levitov, Physical Review Letters 102, 065703 (2009)
2009
-
[49]
Yao and Z
S. Yao and Z. Wang, Physical Review Letters121, 086803 (2018)
2018
-
[50]
F. Song, S. Yao, and Z. Wang, Physical Review Letters 123, 246801 (2019)
2019
-
[51]
Wegner, Zeitschrift f¨ ur Physik B Condensed Matter and Quanta36, 209 (1980)
F. Wegner, Zeitschrift f¨ ur Physik B Condensed Matter and Quanta36, 209 (1980)
1980
-
[52]
Evers and A
F. Evers and A. D. Mirlin, Reviews of Modern Physics 80, 1355 (2008)
2008
-
[53]
P. Calabrese and J. Cardy, Journal of Statistical Me- chanics: Theory and Experiment2005, P04010 (2005), arXiv:cond-mat/0503393
Pith/arXiv arXiv 2005
-
[54]
V. Alba and P. Calabrese, Entanglement dynamics after quantum quenches in generic integrable systems (2018), arXiv:1712.07529
Pith/arXiv arXiv 2018
-
[55]
M. Kac, G. E. Uhlenbeck, and P. C. Hemmer, Journal of Mathematical Physics4, 216 (1963). 1 Supplemental Material Convergence of entanglement entropy to its asymptotic value The asymptotic values are computed at timet= 10 4 ℏ/J, which was checked to be a long enough time to reach saturation for all choices of the parameters used in the numerical simulation...
1963
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