REVIEW 2 major objections 2 minor 3 cited by
Disorder drives a transition out of the ergodic phase in two-dimensional quantum systems.
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 · grok-4.3
2026-05-16 18:33 UTC
load-bearing objection The paper shows experimental power-law Hilbert-space decay and Edwards-Anderson onset in a 2D qubit array at intermediate disorder, but finite-size and coherence effects could mimic the claimed thermodynamic transition. the 2 major comments →
Hilbert space signatures of non-ergodic glassy dynamics
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
In the two-dimensional disordered spin model realized on the qubit array, an intermediate non-ergodic regime appears over a broad disorder range, marked by broadly distributed observables, slow power-law decay of the Hilbert-space return probability, onset of a finite Edwards-Anderson order parameter, and loss of spin diffusion, while lower disorder permits nonzero diffusion coefficient and persistent transport.
What carries the argument
The Hilbert-space return probability combined with the Edwards-Anderson order parameter, which together detect partial freezing of degrees of freedom across the many-body state space.
Load-bearing premise
The measured power-law decay, broad distributions, and order parameter onset mark a true thermodynamic transition rather than finite-size or transient hardware effects.
What would settle it
A demonstration that the Edwards-Anderson parameter vanishes or the return probability decay turns exponential when system size increases at fixed disorder and temperature.
If this is right
- Spin diffusion coefficient drops to zero above a critical disorder strength.
- Physical observables cease to be self-averaging and instead show broad distributions.
- Only a subset of degrees of freedom freeze, leaving others active.
- The system leaves the ergodic phase at finite disorder and finite temperature.
Where Pith is reading between the lines
- The power-law return probability may remain a useful diagnostic for glassiness in the thermodynamic limit.
- Analogous measurements on other two-dimensional platforms could test whether the transition is platform-independent.
- The results suggest finite-temperature 2D many-body glasses may be experimentally accessible without requiring extreme isolation.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript reports experiments on a two-dimensional array of superconducting qubits realizing a disordered interacting spin model at finite temperature. It identifies an intermediate non-ergodic regime with glass-like features: broadly distributed observables, power-law decay of the Hilbert-space return probability, onset of a finite Edwards-Anderson order parameter, and vanishing spin diffusion, while nonzero diffusion persists at weaker disorder. The authors conclude that these signatures establish a transition out of the ergodic phase in two-dimensional systems.
Significance. If the central interpretation is upheld, the result would be significant: it supplies experimental evidence for finite-temperature non-ergodic glassy dynamics in 2D, using both real-space transport and Hilbert-space return probabilities, thereby addressing a debated question in many-body localization and quantum glasses. The experimental platform and dual-space diagnostics constitute a concrete advance.
major comments (2)
- [Abstract and main results] Abstract and main results: the claim that the observed power-law return probability, broad distributions, Edwards-Anderson order-parameter onset, and vanishing diffusion constitute evidence of a thermodynamic transition out of the ergodic phase is load-bearing, yet the manuscript provides no finite-size scaling collapse or explicit coherence-time controls that would exclude transient dynamics cut off by hardware decoherence or finite-size localization that fails to survive the thermodynamic limit.
- [Results on Edwards-Anderson order parameter] The interpretation of the Edwards-Anderson order parameter as marking a true thermodynamic transition requires demonstration that its onset survives extrapolation to larger system sizes or longer coherence times; without such data the finite-size/hardware alternative remains viable.
minor comments (2)
- [Methods] Notation for the Hilbert-space return probability should be defined explicitly at first use with a clear equation reference.
- [Figures] Figure captions should state the number of disorder realizations and the precise fitting windows used for the power-law exponents.
Simulated Author's Rebuttal
We thank the referee for their careful reading of the manuscript and for highlighting the need to strengthen the evidence for a thermodynamic transition. We address each major comment below, providing clarifications based on the experimental data and noting revisions where appropriate. Our responses focus on the multi-probe consistency of the observed signatures while acknowledging hardware constraints.
read point-by-point responses
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Referee: [Abstract and main results] Abstract and main results: the claim that the observed power-law return probability, broad distributions, Edwards-Anderson order-parameter onset, and vanishing diffusion constitute evidence of a thermodynamic transition out of the ergodic phase is load-bearing, yet the manuscript provides no finite-size scaling collapse or explicit coherence-time controls that would exclude transient dynamics cut off by hardware decoherence or finite-size localization that fails to survive the thermodynamic limit.
Authors: We agree that a finite-size scaling collapse would provide more definitive support for a thermodynamic transition in the thermodynamic limit. The current experimental platform uses a fixed-size 2D qubit array, which precludes systematic variation of system size. Instead, we vary disorder strength and observe that the power-law Hilbert-space return probability, broad observable distributions, finite Edwards-Anderson parameter, and vanishing spin diffusion all onset at the same disorder threshold. Additional analysis of the return probability time series shows the power-law regime extends over the full accessible coherence window without premature cutoff by decoherence. We will revise the manuscript to include an expanded discussion of these hardware limitations and the rationale for interpreting the multi-observable crossover as evidence of the non-ergodic regime, consistent with theoretical expectations for 2D quantum glasses. revision: partial
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Referee: [Results on Edwards-Anderson order parameter] The interpretation of the Edwards-Anderson order parameter as marking a true thermodynamic transition requires demonstration that its onset survives extrapolation to larger system sizes or longer coherence times; without such data the finite-size/hardware alternative remains viable.
Authors: The Edwards-Anderson order parameter is obtained from the long-time limit of the disorder-averaged local spin autocorrelations. Within the experimentally accessible coherence times, this parameter saturates to a nonzero value above the critical disorder, coinciding precisely with the suppression of spin diffusion. We have verified that the onset remains stable when varying the averaging window inside the coherence time. While direct extrapolation to infinite size or infinite coherence time is not feasible with the present hardware, the simultaneous disappearance of diffusion at the same disorder value provides independent corroboration that the order parameter reflects dynamical freezing. We will revise the manuscript to add supplementary figures displaying the time dependence of the order parameter and its disorder dependence with error bars to address this point explicitly. revision: yes
- Finite-size scaling collapse cannot be performed because the superconducting qubit array has a fixed number of sites set by the experimental hardware.
Circularity Check
No significant circularity in experimental observations
full rationale
The paper reports direct experimental measurements on a 2D superconducting qubit array, including Hilbert-space return probabilities showing power-law decay, broad distributions of physical observables, onset of a finite Edwards-Anderson order parameter, and the disappearance of spin diffusion at higher disorder. These quantities are obtained as independent hardware observables rather than quantities fitted or defined in terms of each other within the paper. No self-citations, ansatzes, or uniqueness theorems are invoked as load-bearing steps in the provided text to derive the central claim of a transition out of the ergodic phase; the results are presented as empirical evidence without reduction to the inputs by construction.
Axiom & Free-Parameter Ledger
read the original abstract
Disorder in quantum many-body systems can drive transitions between ergodic and non-ergodic phases, yet the nature--and even the existence--of these transitions remains intensely debated. Using a two-dimensional array of superconducting qubits, we study an interacting spin model at finite temperature in a disordered landscape, tracking dynamics both in real space and in Hilbert space. Over a broad disorder range, we observe an intermediate non-ergodic regime with glass-like characteristics: physical observables become broadly distributed and some, but not all, degrees of freedom are effectively frozen. The Hilbert-space return probability shows slow power-law decay, consistent with finite-temperature quantum glassiness. In the same regime, we detect the onset of a finite Edwards-Anderson order parameter and the disappearance of spin diffusion. By contrast, at lower disorder, spin transport persists with a nonzero diffusion coefficient. Our results show that there is a transition out of the ergodic phase in two-dimensional systems.
Figures
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Reference graph
Works this paper leans on
-
[1]
have enabled numerous studies of ergodicity and its breakdown. Most MBL investigations have focused on the real-space phenomenology, particularly by studying the relaxation rates and asymptotic behaviour of popula- tion imbalance [49–53]. These experiments are demand- ing in terms of the number of disorder realizations and repetitions required, readily ad...
-
[2]
D. M. Basko, I. L. Aleiner, and B. L. Altshuler, Metal–insulator transition in a weakly interacting many- electron system with localized single-particle states, An- nals of Physics321, 1126 (2006)
work page 2006
-
[3]
E. Altman and R. Vosk, Universal dynamics and renor- malization in many-body-localized systems, Annu. Rev. Condens. Matter Phys.6, 383 (2015)
work page 2015
-
[4]
R. Nandkishore and D. A. Huse, Many-body localiza- tion and thermalization in quantum statistical mechan- ics, Annu. Rev. Condens. Matter Phys.6, 15 (2015)
work page 2015
-
[5]
D. J. Luitz and Y. B. Lev, The ergodic side of the many- body localization transition, Annalen der Physik529, 1600350 (2017)
work page 2017
-
[6]
F. Alet and N. Laflorencie, Many-body localization: An introduction and selected topics, Comptes Rendus Physique19, 498 (2018)
work page 2018
-
[7]
S. Gopalakrishnan and D. A. Huse, Instability of many- body localized systems as a phase transition in a non- standard thermodynamic limit, Physical Review B99, 134305 (2019)
work page 2019
-
[8]
D. A. Abaninet al., Colloquium: Many-body localiza- tion, thermalization, and entanglement, Rev. Mod. Phys. 9 91, 021001 (2019)
work page 2019
-
[9]
J. Suntajs, J. Bonˇ ca, T. Prosen, and L. Vidmar, Quan- tum chaos challenges many-body localization, Physical Review E102, 062144 (2020)
work page 2020
-
[10]
D. Sels and A. Polkovnikov, Dynamical obstruction to localization in a disordered spin chain, Physical Review E104, 054105 (2021)
work page 2021
-
[11]
J. C. Peacock and D. Sels, Many-body delocalization from embedded thermal inclusion, Physical Review B 108, L020201 (2023)
work page 2023
-
[12]
P. Sierant, M. Lewenstein, A. Scardicchio, L. Vidmar, and J. Zakrzewski, Many-body localization in the age of classical computing, Reports on Progress in Physics88, 026502 (2025)
work page 2025
-
[13]
S. F. Edwards and P. W. Anderson, Theory of spin glasses, Journal of Physics F: Metal Physics5, 965 (1975)
work page 1975
-
[14]
K. Binder and A. P. Young, Spin glasses: Experimental facts, theoretical concepts, and open questions, Reviews of Modern Physics58, 801 (1986)
work page 1986
-
[15]
M. M´ ezard, G. Parisi, and M. A. Virasoro,Spin Glass Theory and Beyond(World Scientific, 1987)
work page 1987
-
[16]
J.-P. Bouchaud, L. F. Cugliandolo, J. Kurchan, and M. Mezard, ”Out of Equilibrium dynamics in Spin- Glasses and other Glassy Systems”, in ”Spin Glasses and Random Fields”, ed. A.P.Young, World Scientific (1998)
work page 1998
-
[17]
E. Vincent, ”Ageing, Rejuvenation and Memory: The Example of Spin Glasses”, in ”Ageing and the Glass Transition”, eds. M.Henkel, M.Pleimling and R.Sanctuary, Springer, Berlin Heidelberg (2009)
work page 2009
-
[18]
P. Esquinazi,Tunneling systems in amorphous and crys- talline solids(Springer - Verlag, Berlin Heidelberg New York, 1998)
work page 1998
-
[19]
Kogan,Electronic Noise and Fluctuations in Solids (Cambridge University Press, 2008)
S. Kogan,Electronic Noise and Fluctuations in Solids (Cambridge University Press, 2008)
work page 2008
-
[20]
Paladinoet al., 1/f noise: implications for solid-state quantum information, Rev
E. Paladinoet al., 1/f noise: implications for solid-state quantum information, Rev. Mod. Phys.86, 361 (2014)
work page 2014
-
[21]
P. Charbonneau, E. Marinari, G. Parisi, F. Ricci- tersenghi, G. Sicuro, F. Zamponi, and M. Mezard,Spin glass theory and far beyond: replica symmetry breaking after 40 years(World Scientific, 2023)
work page 2023
-
[22]
W. De Roeck, L. Giacomin, F. Huveneers, and O. Pros- niak, Absence of normal heat conduction in strongly disordered interacting quantum chains, arXiv preprint arXiv:2408.04338 (2024)
-
[23]
J. Z. Imbrie, On many-body localization for quantum spin chains, Journal of Statistical Physics163, 998 (2016)
work page 2016
- [24]
-
[25]
E. V. Doggenet al., Slow many-body delocalization beyond one dimension, Phys. Rev. Lett.125, 155701 (2020)
work page 2020
-
[26]
J. Li, A. Chan, and T. B. Wahl, Quantum circuits repro- duce the experimental two-dimensional many-body lo- calization transition point, Phys. Rev. B109, L140202 (2024)
work page 2024
-
[27]
J. Li, A. Chan, and T. B. Wahl, Two-dimensional many- body localized systems coupled to a heat bath, Phys. Rev. B111, 224211 (2025)
work page 2025
-
[28]
K. Tikhonov and A. Mirlin, Statistics of eigenstates near the localization transition on random regular graphs, Physical Review B99, 024202 (2019)
work page 2019
-
[29]
V. E. Kravtsov, I. M. Khaymovich, E. Cuevas, and M. Amini, A random matrix model with localization and ergodic transitions, New J. Phys.17, 122002 (2015)
work page 2015
-
[30]
G. D. Tomasiet al., Survival probability in general- ized rosenzweig-porter random matrix ensemble, SciPost Physics6, 014 (2019)
work page 2019
-
[31]
G. Biroli and M. Tarzia, Fractal and nonergodic phases in random matrix models, Phys. Rev. B103, 104205 (2021)
work page 2021
-
[32]
A. V. Lunkin and K. Tikhonov, Local density of states correlations in the L´ evy-Rosenzweig-Porter random ma- trix ensemble, SciPost Physics19, 015 (2025)
work page 2025
-
[33]
E. Safonova, A. Lunkin, and M. Feigel’man, Density of states correlations in L´ evy Rosenzweig-Porter model via supersymmetry approach, SciPost Phys.20, 003 (2026)
work page 2026
- [34]
-
[35]
V. N. Smelyanskiyet al., Nonergodic delocalized states for efficient population transfer within a narrow band of the energy landscape, Phys. Rev. X10, 011017 (2020)
work page 2020
-
[36]
Wineret al., Spectral form factor of a quantum spin glass, J
M. Wineret al., Spectral form factor of a quantum spin glass, J. High Energy Phys.2022, 32
work page 2022
-
[37]
M. Mezard and A. Montanari,Information, physics, and computation(Oxford University Press, 2009)
work page 2009
-
[38]
Y. B. Levet al., Absence of diffusion in an interacting system of spinless fermions on a one-dimensional disor- dered lattice, Phys. Rev. Lett.114, 100601 (2015)
work page 2015
-
[39]
K. Agarwalet al., Anomalous diffusion and griffiths ef- fects near the many-body localization transition, Phys. Rev. Lett.114, 160401 (2015)
work page 2015
- [40]
-
[41]
Pinoet al., Nonergodic metallic and insulating phases of josephson junction chains, Proc
M. Pinoet al., Nonergodic metallic and insulating phases of josephson junction chains, Proc. Natl. Acad. Sci. U.S.A.113, 536 (2016)
work page 2016
-
[42]
M. Pino, V. Kravtsov, B. Altshuler, and L. Ioffe, Multi- fractal metal in a disordered josephson junctions array, Physical Review B96, 214205 (2017)
work page 2017
-
[43]
D. M. Long, P. J. D. Crowley, V. Khemani, and A. Chan- dran, Phenomenology of the prethermal many-body lo- calized regime, Phys. Rev. Lett.131, 106301 (2023)
work page 2023
-
[44]
Tarzia, Many-body localization transition in hilbert space, Phys
M. Tarzia, Many-body localization transition in hilbert space, Phys. Rev. B102, 014208 (2020)
work page 2020
-
[45]
G. Biroliet al., Large-deviation analysis of rare reso- nances for the many-body localization transition, Phys. Rev. B110, 014205 (2024)
work page 2024
-
[46]
Thieryet al., Many-body delocalization as a quantum avalanche, Phys
T. Thieryet al., Many-body delocalization as a quantum avalanche, Phys. Rev. Lett.121, 140601 (2018)
work page 2018
-
[47]
W. D. Roeck and F. Huveneers, Stability and instabil- ity towards delocalization in many-body localization sys- tems, Phys. Rev. B95, 155129 (2017)
work page 2017
-
[48]
S. Gopalakrishnanet al., Griffiths effects and slow dy- namics in nearly many-body localized systems, Phys. Rev. B93, 134206 (2016)
work page 2016
-
[49]
Altmanet al., Quantum simulators: Architectures and opportunities, PRX Quantum2, 017003 (2021)
E. Altmanet al., Quantum simulators: Architectures and opportunities, PRX Quantum2, 017003 (2021)
work page 2021
-
[50]
M. Schreiberet al., Observation of many-body localiza- tion of interacting fermions in a quasirandom optical lat- tice, Science349, 842 (2015)
work page 2015
-
[51]
J.-y. Choi, S. Hild, J. Zeiher, P. Schauss, A. Rubio- Abadal, T. Yefsah, V. Khemani, D. Huse, I. Bloch, and C. Gross, Exploring the many-body localization transi- tion in two dimensions, Science352, 1547 (2016). 10
work page 2016
-
[52]
P. Bordiaet al., Periodically driving a many-body local- ized quantum system, Nature Physics13, 460 (2017)
work page 2017
- [53]
-
[54]
Yu,A.Chan,T.Wahl,andJ.yoonChoi,Stabilityofmany-body localization in two dimensions, arXiv:2508.20699
J. Huret al., Stability of many-body localization in two dimensions, arXiv preprint arXiv:2508.20699 (2025)
-
[55]
M. Kjaergaard, M. E. Schwartz, J. Braum¨ uller, P. Krantz, J. I.-J. Wang, S. Gustavsson, and W. D. Oliver, Superconducting qubits: Current state of play, Annual Review of Condensed Matter Physics11, 369 (2020)
work page 2020
-
[56]
J. P. A. Z´ unigaet al., Critical properties of the superfluid - boseglass transition in two dimensions, Phys. Rev. Lett. 114, 155301 (2015)
work page 2015
-
[57]
L. Leviandieret al., Fourier transform: A tool to measure statistical level properties in very complex spectra, Phys. Rev. Lett.56, 2449 (1986)
work page 1986
-
[58]
E. J. Torres-Herreraet al., Generic dynamical features of quenched interacting quantum systems: Survival proba- bility, density imbalance, and out-of-time-ordered corre- lator, Phys. Rev. B97, 060303(R) (2018)
work page 2018
-
[59]
E. J. Torres-Herrera and L. F. Santos, Dynamics at the many-body localization transition, Phys. Rev. B92, 014208 (2016)
work page 2016
-
[60]
M. Hopjan and L. Vidmar, Scale-invariant survival prob- ability at eigenstate transitions, Phys. Rev. Lett.131, 060404 (2023)
work page 2023
-
[61]
M. Hopjan and L. Vidmar, Scale-invariant critical dy- namics at eigenstate transitions, Phys. Rev. Res.5, 043301 (2023)
work page 2023
-
[62]
C. E. Porter and R. G. Thomas, Fluctuations of nuclear reaction widths, Phys. Rev.104, 483 (1956)
work page 1956
-
[63]
Since our dynamics conserves total spin projectionS z tot = 0, the Hilbert space dimension is equal toN=n!/( n 2 !)2
-
[64]
B. Altshulr, V. Kravtsov, and I. Lerner, Statistics of mesoscopic fluctuations and instability of one-parameter scaling, Sov.Phys.-JETP64, 1352 (1986)
work page 1986
-
[65]
V. I. Fal’ko and K. B. Efetov, Statistics of prelocalized states in disordered conductors, Phys. Rev. B52, 17413 (1995)
work page 1995
-
[66]
A. Mirlin and F. Evers, Anderson transitions, Rev. Mod. Phys.80, 1355 (2008)
work page 2008
-
[67]
A. De Luca, B. L. Altshuler, V. E. Kravtsov, and A. Scardicchio, Anderson localization on the bethe lat- tice: Nonergodicity of extended states, Phys. Rev. Lett. 113, 046806 (2014)
work page 2014
-
[68]
L. F. Cugliandolo, G. Schehr, M. Tarzia, and D. Ven- turelli, Multifractal phase in the weighted adjacency ma- trices of random erd¨ os-r´ enyi graphs, Phys. Rev. B110, 174202 (2024)
work page 2024
-
[69]
Support set of random wave-functions on the Bethe lattice
A. De Luca, B. L. Altshuler, V. E. Kravtsov, and A. Scardicchio, Support set of random wave- functions on the bethe lattice, arXiv preprint (2014), arXiv:1401.0019
work page internal anchor Pith review Pith/arXiv arXiv 2014
-
[70]
J. H. Bardarson, F. Pollmann, and J. E. Moore, Un- bounded growth of entanglement in models of many-body localization, Phys. Rev. Lett.109, 017202 (2012)
work page 2012
-
[71]
Google Quantum AI, Quantum error correction below the surface code threshold, Nature638, 920 (2025)
work page 2025
-
[72]
T. I. Andersen, N. Astrakhantsev, A. H. Karamlou, J. Berndtsson, J. Motruk, A. Szasz, J. A. Gross, A. Schuckert, T. Westerhout, Y. Zhang,et al., Thermal- ization and criticality on an analogue–digital quantum simulator, Nature638, 79 (2025)
work page 2025
-
[73]
W. A. Phillips, Two-level states in glasses, Reports on Progress in Physics50, 1657 (1987)
work page 1987
-
[74]
D. B. Gutmanet al., Energy transport in the anderson insulator, Phys. Rev. B93, 245427 (2016)
work page 2016
-
[75]
L. Faoro and L. B. Ioffe, Internal loss of superconduct- ing resonators induced by interacting two-level systems, Phys. Rev. Lett.109, 157005 (2012)
work page 2012
-
[76]
V. K. Varmaet al., Energy diffusion in the ergodic phase of a many-body localizable spin chain, J. Stat. Mech. , 053101 (2017)
work page 2017
-
[77]
J. Herbrych and P. Prelovsek, Spin and energy diffusion versus subdiffusion in disordered spin chains, Phys. Rev. B112, 045108 (2025)
work page 2025
-
[78]
M. V. Feigel’man, L. B. Ioffe, and M. M´ ezard, Superconductor-insulator transition and energy localiza- tion, Phys. Rev. B82, 184534 (2010)
work page 2010
-
[79]
R. Abou-Chacra, D. J. Thouless, and P. W. Anderson, A self-consistent theory of localization, J. Phys. C6, 1734 (1973)
work page 1973
-
[80]
V. E. Kravtsov, B. L. Altshuler, and L. B. Ioffe, Non- ergodic extended states in disordered systems, Ann. Phys.389, 148 (2018)
work page 2018
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