REVIEW 2 major objections 1 cited by
Distinguishing Ordered Phases using Machine Learning and Classical Shadows
T0 review · 2 major / 0 minor · reviewed 2026-05-23 · grok-4.3
Pith's one-line read Classical shadows of local observables fed to unsupervised clustering can distinguish ordered phases in quantum spin models even with few qubits.
desk verdict The paper applies classical shadows on local observables plus unsupervised clustering to separate phases in two spin models, but the abstract supplies no numbers to back the log-scaling claim or rule out noise-driven clusters. 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
Classical shadows protocol restricted to pairwise correlations and plaquette operators, whose estimates are clustered by unsupervised machine learning.
What would settle it
Running the protocol on the benchmark models with increasing numbers of shadows and finding that the learned clusters fail to separate at the known phase boundaries.
Extended reading notes
Core claim
By estimating a small set of local observables through classical shadows and passing the resulting vectors to an unsupervised clustering algorithm, the distinct ordered phases of the axial next-nearest-neighbor Ising model and the Kitaev-Heisenberg two-leg ladder become separable, even when the system size is limited to a few qubits; the sample complexity of the shadow protocol scales only logarithmically with the number of measured features.
Load-bearing premise
The unsupervised clusters formed from the estimated local observables will correspond to the physically distinct ordered phases rather than to sampling noise or other artifacts.
Editorial extensions
If this is right
- Phase diagrams of spin models become accessible from local measurements on systems too large for exact diagonalization.
- Sample overhead remains modest when the observable set is kept small and local.
- The same pipeline applies without modification to other one- and two-dimensional Hamiltonians whose phases are characterized by local order parameters.
Reading between the lines
- The method could be applied directly to experimental data from quantum simulators that can measure only two-body correlators.
- If the logarithmic scaling holds for larger feature sets, the approach may extend to distinguishing topological phases that require slightly nonlocal but still efficiently estimable operators.
- The framework supplies a concrete numerical test for whether a given set of local observables is sufficient to resolve a particular phase diagram.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript proposes a framework combining classical shadows with unsupervised machine learning to identify quantum phase transitions. It benchmarks the approach on the axial next-nearest-neighbor Ising model and the Kitaev-Heisenberg ladder, asserting that phases can be distinguished even with few qubits via clustering of local observables (pairwise correlations, plaquette operators) and that sample complexity scales logarithmically with the number of features.
Significance. If the unsupervised clustering of shadow-estimated observables is shown to align with physical order parameters rather than noise or finite-size artifacts, the method would offer a scalable route to phase classification in regimes where exact methods fail, exploiting the efficiency of classical shadows for restricted local features.
major comments (2)
- [Abstract] Abstract: The central claim that unsupervised ML 'can effectively distinguish' the phases rests on the unverified assumption that clusters of estimated local observables align with known physical phase boundaries. No quantitative metrics (accuracy, adjusted Rand index, or comparison to exact phase diagrams), error bars, or ablation on the clustering algorithm are supplied, leaving open whether results reflect order parameters or sampling artifacts in the median-of-means estimator.
- [Abstract] Abstract: The stated logarithmic scaling of sample complexity with the number of measured features is asserted without derivation, explicit bound, or numerical demonstration on the benchmark models; this scaling is load-bearing for the scalability claim but is not shown to hold after accounting for the variance of the shadow estimator on the chosen observables.
Simulated Author's Rebuttal
We thank the referee for their careful reading and constructive comments. The points raised about validation metrics and the sample-complexity claim are well taken; we address each below and will revise the manuscript to incorporate additional quantitative evidence and derivations.
read point-by-point responses
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Referee: [Abstract] Abstract: The central claim that unsupervised ML 'can effectively distinguish' the phases rests on the unverified assumption that clusters of estimated local observables align with known physical phase boundaries. No quantitative metrics (accuracy, adjusted Rand index, or comparison to exact phase diagrams), error bars, or ablation on the clustering algorithm are supplied, leaving open whether results reflect order parameters or sampling artifacts in the median-of-means estimator.
Authors: We agree that quantitative validation strengthens the central claim. In the revised manuscript we will report adjusted Rand index values between the unsupervised clusters and the known phase labels obtained from exact diagonalization, include error bars obtained from independent shadow realizations, and add an ablation study comparing k-means, hierarchical clustering, and DBSCAN. These additions will directly address whether the observed clusters track physical order parameters rather than estimator artifacts. revision: yes
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Referee: [Abstract] Abstract: The stated logarithmic scaling of sample complexity with the number of measured features is asserted without derivation, explicit bound, or numerical demonstration on the benchmark models; this scaling is load-bearing for the scalability claim but is not shown to hold after accounting for the variance of the shadow estimator on the chosen observables.
Authors: The logarithmic dependence follows from standard concentration arguments for median-of-means estimators applied to a fixed collection of local observables, but we acknowledge that an explicit derivation that folds in the shadow-norm variance of the specific pairwise-correlation and plaquette operators, together with numerical verification on the ANNNI and Kitaev-Heisenberg ladders, was not supplied. We will add both the derivation and the corresponding numerical checks in the revised manuscript. revision: yes
Circularity Check
No circularity: empirical framework tested on benchmarks without self-referential derivations
full rationale
The paper presents a computational framework combining classical shadows with unsupervised ML, tested empirically on standard benchmark models (axial next-nearest-neighbor Ising and Kitaev-Heisenberg ladder). No equations, derivations, or load-bearing steps are shown that reduce claims to fitted parameters, self-definitions, or self-citation chains. The logarithmic scaling claim follows directly from the restricted observable set in the classical shadows protocol, which is an established property independent of the ML clustering step. The central assertion that clusters align with phases is validated by numerical experiments on known Hamiltonians rather than by construction. This is a self-contained empirical study with no detected circularity patterns.
Assumptions & free parameters
Cite this review
Pith. "Pith review of Distinguishing Ordered Phases using Machine Learning and Classical Shadows." pith.science (2026). https://pith.science/paper/AZBAF6GR
@misc{pith2026250117837,
author = {Pith},
title = {Pith review of: Distinguishing Ordered Phases using Machine Learning and Classical Shadows},
year = {2026},
howpublished = {\url{https://pith.science/paper/AZBAF6GR}},
note = {Machine review of arXiv:2501.17837}
}
read the original abstract
Classifying phase transitions is a fundamental and complex challenge in condensed matter physics. This work proposes a framework for identifying quantum phase transitions by combining classical shadows with unsupervised machine learning. We use the axial next-nearest neighbor Ising model as our benchmark and extend the analysis to the Kitaev-Heisenberg model on a two-leg ladder. Even with few qubits, we can effectively distinguish between the different phases of the Hamiltonian models. {Furthermore, by relying on a restricted set of local observables, such as pairwise correlations and plaquette operators, the sample complexity of the classical shadows protocol scales logarithmically with the number of measured features. This makes our approach a scalable and efficient tool for studying phase transitions in larger many-body systems where classical verification becomes intractable.
Forward citations
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Reference graph
Works this paper leans on
-
[1]
and the Kitaev-Heisenberg ladder [ 22]. Both models are relevant for describing the magnetic properties of real materials and display rich phase diagrams with multiple ordered and disordered phases. The ANNNI model is significant as the simplest model in which different types of competing magnetic orders stem from the interplay between frustrated Ising in...
-
[2]
In this phase, the system spontaneously breaks the Z2 symmetry σz j 7→ −σz j
For small k and g, the system is in the ferromagnetic phase. In this phase, the system spontaneously breaks the Z2 symmetry σz j 7→ −σz j . The two degenerate ground states are adiabatically connected to the product states in which the spins order themselves either as ↑↑ · · · ↑↑ or as ↓↓ · · · ↓↓ ; 3 FIG. 2. The Kitaev-Heisenberg ladder. Blue, green and ...
-
[3]
For large enough g, the transverse field term dominates and the system enters a paramagnetic disordered phase, with a unique ground state of spins aligned with the field
- [4]
-
[5]
For a small region of intermediate k and g, the system is in a gapless "floating phase" with power- law-decaying correlations. The phase diagram of the ANNNI chain as a function of k and g is shown in Fig. 1. The ANNNI model has a wide range of practical applications, including the description of rare-earth metals [ 26, 39], the explanation of magnetic or...
-
[6]
A rung-singlet (RS) phase for −0.3π ≤ ϕ ≤ 0.48π, a trivial phase without magnetic order, where the unique ground state is adiabatically connected to a product of singlets on the rungs
-
[7]
This corresponds to a narrow region around the pure Kitaev limit at ϕ = π 2 , where J = 0 and K = 1
An antiferromagnetic Kitaev spin liquid (AFK) phase for 0.48π < ϕ < 0.53π. This corresponds to a narrow region around the pure Kitaev limit at ϕ = π 2 , where J = 0 and K = 1
-
[8]
The zigzag (ZZ) phase (named after its analog phase in the honeycomb lattice) for 0.53 π ≤ ϕ < FIG. 5. Pictorial representation of neighbors and diagonal pairwise correlations for a states in different phases of a fictitious system 0.8π. This phase has ferromagnetic order on each leg, but the magnetization has opposite signs on different legs
Show all 67 references
-
[9]
A ferromagnetic (FM) phase for 0.8 π ≤ ϕ < 1.37π, in the region around ϕ = π, where J = −1 and K = 0 ensure ferromagnetic Heisenberg interactions between the spins
-
[10]
Interestingly, this spin liquid phase is significantly wider than its antiferromagnetic counterpart
A ferromagnetic Kitaev spin liquid (FK) phase for 1.37π ≤ ϕ ≤ 1.57ϕ, the region around ϕ = 3π 2 , where J = 0 and K = −1. Interestingly, this spin liquid phase is significantly wider than its antiferromagnetic counterpart
-
[11]
snapshot
The stripy (ST) phase for 1.57 π < ϕ < 1.7π, with long-range antiferromagnetic order along each leg but ferromagnetic correlations between spins on the same rung. The phases of the Kitaev-Heisenberg model described above are shown in Figure 3. An interesting point to note abou...
2022
-
[12]
Solving the quantum many-body problem with artificial neural networks
Giuseppe Carleo and Matthias Troyer. Solving the quantum many-body problem with artificial neural networks. Science, 355(6325):602–606, 2017
2017
-
[13]
Neural-network quantum state tomography
Giacomo Torlai, Guglielmo Mazzola, Juan Carrasquilla, Matthias Troyer, Roger Melko, and Giuseppe Carleo. Neural-network quantum state tomography. Nature physics, 14(5):447–450, 2018. 11
2018
-
[14]
Machine learning and the physical sciences
Giuseppe Carleo, Ignacio Cirac, Kyle Cranmer, Laurent Daudet, Maria Schuld, Naftali Tishby, Leslie Vogt- Maranto, and Lenka Zdeborová. Machine learning and the physical sciences. Reviews of Modern Physics , 91(4):045002, 2019
2019
-
[15]
Machine learning for quantum matter
Juan Carrasquilla. Machine learning for quantum matter. Advances in Physics: X , 5(1):1797528, 2020
2020
-
[16]
Predicting many properties of a quantum system from very few measurements
Hsin-Yuan Huang, Richard Kueng, and John Preskill. Predicting many properties of a quantum system from very few measurements. Nature Physics , 16(10):1050– 1057, 2020
2020
-
[17]
Machine learning phases of matter
Juan Carrasquilla and Roger G Melko. Machine learning phases of matter. Nature Physics, 13(5):431–434, 2017
2017
-
[18]
Machine learning of quantum phase transitions
Xiao-Yu Dong, Frank Pollmann, and Xue-Feng Zhang. Machine learning of quantum phase transitions. Phys. Rev. B, 99:121104, Mar 2019
2019
-
[19]
Unsupervised machine learning of quantum phase transitions using diffusion maps
Alexander Lidiak and Zhexuan Gong. Unsupervised machine learning of quantum phase transitions using diffusion maps. Phys. Rev. Lett., 125:225701, Nov 2020
2020
-
[20]
Machine learning quantum phases of matter beyond the fermion sign problem
Peter Broecker, Juan Carrasquilla, Roger G Melko, and Simon Trebst. Machine learning quantum phases of matter beyond the fermion sign problem. Scientific reports, 7(1):8823, 2017
2017
-
[21]
Identifying topological order through unsupervised machine learning
Joaquin F Rodriguez-Nieva and Mathias S Scheurer. Identifying topological order through unsupervised machine learning. Nature Physics, 15(8):790–795, 2019
2019
-
[22]
Machine learning of quantum phase transitions
Xiao-Yu Dong, Frank Pollmann, and Xue-Feng Zhang. Machine learning of quantum phase transitions. Physical Review B, 99(12):121104, 2019
2019
-
[23]
Machine learning phase transitions with a quantum processor
AV Uvarov, AS Kardashin, and Jacob D Biamonte. Machine learning phase transitions with a quantum processor. Physical Review A, 102(1):012415, 2020
2020
-
[24]
Predicting topological invariants and unconventional superconducting pairing from density of states and machine learning
Flavio Noronha, Askery Canabarro, Rafael Chaves, and Rodrigo G Pereira. Predicting topological invariants and unconventional superconducting pairing from density of states and machine learning. arXiv preprint arXiv:2408.16499, 2024
2024
-
[25]
Topological quantum phase transitions retrieved through unsupervised machine learning
Yanming Che, Clemens Gneiting, Tao Liu, and Franco Nori. Topological quantum phase transitions retrieved through unsupervised machine learning. Phys. Rev. B , 102:134213, Oct 2020
2020
-
[26]
Quantum monte carlo simulations of solids
William MC Foulkes, Lubos Mitas, RJ Needs, and Guna Rajagopal. Quantum monte carlo simulations of solids. Reviews of Modern Physics, 73(1):33, 2001
2001
-
[27]
Efficient quantum state tomography
Marcus Cramer, Martin B Plenio, Steven T Flammia, Rolando Somma, David Gross, Stephen D Bartlett, Olivier Landon-Cardinal, David Poulin, and Yi-Kai Liu. Efficient quantum state tomography. Nature communications, 1(1):149, 2010
2010
-
[28]
Challenges and opportunities in quantum machine learning
Marco Cerezo, Guillaume Verdon, Hsin-Yuan Huang, Lukasz Cincio, and Patrick J Coles. Challenges and opportunities in quantum machine learning. Nature Computational Science, 2(9):567–576, 2022
2022
-
[29]
Training variational quantum algorithms is np-hard
Lennart Bittel and Martin Kliesch. Training variational quantum algorithms is np-hard. Physical review letters , 127(12):120502, 2021
2021
-
[30]
Power of data in quantum machine learning
Hsin-Yuan Huang, Michael Broughton, Masoud Mohseni, Ryan Babbush, Sergio Boixo, Hartmut Neven, and Jarrod R McClean. Power of data in quantum machine learning. Nature communications , 12(1):2631, 2021
2021
-
[31]
Shadow tomography of quantum states
Scott Aaronson. Shadow tomography of quantum states. In Proceedings of the 50th annual ACM SIGACT symposium on theory of computing, pages 325–338, 2018
2018
-
[32]
The annni model—theoretical analysis and experimental application
Walter Selke. The annni model—theoretical analysis and experimental application. Physics Reports, 170(4):213–264, 1988
1988
-
[33]
Sørensen, and Hae-Young Kee
Andrei Catuneanu, Erik S. Sørensen, and Hae-Young Kee. Nonlocal string order parameter in the S = 1 2 Kitaev-Heisenberg ladder. Phys. Rev. B , 99:195112, May 2019
2019
-
[34]
Topological characterization of quantum phase transitions in a spin-1/2 model
Xiao-Yong Feng, Guang-Ming Zhang, and Tao Xiang. Topological characterization of quantum phase transitions in a spin-1/2 model. Phys. Rev. Lett. , 98:087204, Feb 2007
2007
-
[35]
Hidenori Takagi, Tomohiro Takayama, George Jackeli, Giniyat Khaliullin, and Stephen E. Nagler. Concept and realization of Kitaev quantum spin liquids. Nature Reviews Physics, 1(4):264–280, 2019
2019
-
[36]
Least squares quantization in pcm
Stuart Lloyd. Least squares quantization in pcm. IEEE transactions on information theory, 28(2):129–137, 1982
1982
-
[37]
R. J. Elliott. Phenomenological discussion of magnetic ordering in the heavy rare-earth metals. Phys. Rev. , 124:346–353, Oct 1961
1961
-
[38]
Villain and P
J. Villain and P . Bak. Two-dimensional ising model with competing interactions : floating phase, walls and dislocations. Journal de Physique, 42(5):657–668, 1981
1981
-
[39]
A two-leg quantum ising ladder: a bosonization study of the ANNNI model
D Allen, P Azaria, and P Lecheminant. A two-leg quantum ising ladder: a bosonization study of the ANNNI model. Journal of Physics A: Mathematical and General, 34(21):L305–L310, may 2001
2001
-
[40]
The one-dimensional ANNNI model in a transverse field: analytic and numerical study of effective hamiltonians
Heiko Rieger and Genadi Uimin. The one-dimensional ANNNI model in a transverse field: analytic and numerical study of effective hamiltonians. Zeitschrift für Physik B Condensed Matter, 101(4):597–611, dec 1996
1996
-
[41]
Colares Guimarães, João A
Paulo R. Colares Guimarães, João A. Plascak, Francisco C. Sá Barreto, and João Florencio. Quantum phase transitions in the one-dimensional transverse ising model with second-neighbor interactions. Phys. Rev. B , 66:064413, Aug 2002
2002
-
[42]
Evidence for a floating phase of the transverse annni model at high frustration
Matteo Beccaria, Massimo Campostrini, and Alessandra Feo. Evidence for a floating phase of the transverse annni model at high frustration. Phys. Rev. B , 76:094410, Sep 2007
2007
-
[43]
Exploring phase transitions by finite- entanglement scaling of MPS in the 1d ANNNI model
Adam Nagy. Exploring phase transitions by finite- entanglement scaling of MPS in the 1d ANNNI model. New Journal of Physics, 13(2):023015, feb 2011
2011
-
[44]
Anyons in an exactly solved model and beyond
Alexei Kitaev. Anyons in an exactly solved model and beyond. Annals of Physics , 321(1):2–111, 2006. January Special Issue
2006
-
[45]
Pereira and Reinhold Egger
Rodrigo G. Pereira and Reinhold Egger. Electrical Access to Ising Anyons in Kitaev Spin Liquids. Phys. Rev. Lett., 125:227202, Nov 2020
2020
-
[46]
A.Yu. Kitaev. Fault-tolerant quantum computation by anyons. Annals of Physics, 303(1):2–30, 2003
2003
-
[47]
Kitaev-Heisenberg Model on a Honeycomb Lattice: Possible Exotic Phases in Iridium Oxides A2IrO3
Ji ˇ rí Chaloupka, George Jackeli, and Giniyat Khaliullin. Kitaev-Heisenberg Model on a Honeycomb Lattice: Possible Exotic Phases in Iridium Oxides A2IrO3. Phys. Rev. Lett., 105:027204, Jul 2010
2010
-
[48]
Manni, J
Yogesh Singh, S. Manni, J. Reuther, T. Berlijn, R. Thomale, W. Ku, S. Trebst, and P . Gegenwart. Relevance of the Heisenberg-Kitaev Model for the Honeycomb Lattice 12 Iridates A2IrO3. Phys. Rev. Lett., 108:127203, Mar 2012
2012
-
[49]
M. Cea, M. Grossi, S. Monaco, E. Rico, L. Tagliacozzo, and S. Vallecorsa. Exploring the phase diagram of the quantum one-dimensional annni model, 2024
2024
-
[50]
The annni model — theoretical analysis and experimental application
Walter Selke. The annni model — theoretical analysis and experimental application. Physics Reports , 170(4):213–264, 1988
1988
-
[51]
Unveiling phase transitions with machine learning
Askery Canabarro, Felipe Fernandes Fanchini, André Luiz Malvezzi, Rodrigo Pereira, and Rafael Chaves. Unveiling phase transitions with machine learning. Phys. Rev. B, 100:045129, Jul 2019
2019
-
[52]
J.-J. Wen, W. Tian, V . O. Garlea, S. M. Koohpayeh, T. M. McQueen, H.-F. Li, J.-Q. Yan, J. A. Rodriguez- Rivera, D. Vaknin, and C. L. Broholm. Disorder from order among anisotropic next-nearest-neighbor Ising spin chains in SrHo2O4. Phys. Rev. B, 91:054424, Feb 2015
2015
-
[53]
Karrasch and D
C. Karrasch and D. Schuricht. Dynamical phase transitions after quenches in nonintegrable models. Phys. Rev. B, 87:195104, May 2013
2013
-
[54]
Strongly interacting majorana modes in an array of josephson junctions
Fabian Hassler and Dirk Schuricht. Strongly interacting majorana modes in an array of josephson junctions. New Journal of Physics, 14(12):125018, dec 2012
2012
-
[55]
Milsted, L
A. Milsted, L. Seabra, I. C. Fulga, C. W. J. Beenakker, and E. Cobanera. Statistical translation invariance protects a topological insulator from interactions. Phys. Rev. B , 92:085139, Aug 2015
2015
-
[56]
Unveiling phase transitions with machine learning
Askery Canabarro, Felipe Fernandes Fanchini, André Luiz Malvezzi, Rodrigo Pereira, and Rafael Chaves. Unveiling phase transitions with machine learning. Physical Review B, 100(4):045129, 2019
2019
-
[57]
Detecting quantum phase transitions in a frustrated spin chain via transfer learning of a quantum classifier algorithm
André J Ferreira-Martins, Leandro Silva, Alberto Palhares, Rodrigo Pereira, Diogo O Soares-Pinto, Rafael Chaves, and Askery Canabarro. Detecting quantum phase transitions in a frustrated spin chain via transfer learning of a quantum classifier algorithm. Physical Review A, 109...
2024
-
[58]
Quantum spin liquids: a review
Lucile Savary and Leon Balents. Quantum spin liquids: a review. Rep. Prog. Phys., 80(1):016502, nov 2016
2016
-
[59]
Broholm, R
C. Broholm, R. J. Cava, S. A. Kivelson, D. G. Nocera, M. R. Norman, and T. Senthil. Quantum spin liquids. Science, 367(6475):eaay0668, 2020
2020
-
[60]
Ground state and low-energy excitations of the Kitaev-Heisenberg two-leg ladder
Cliò Efthimia Agrapidis, Jeroen van den Brink, and Satoshi Nishimoto. Ground state and low-energy excitations of the Kitaev-Heisenberg two-leg ladder. Phys. Rev. B, 99:224418, Jun 2019
2019
-
[61]
Rau, Eric Kin-Ho Lee, and Hae-Young Kee
Jeffrey G. Rau, Eric Kin-Ho Lee, and Hae-Young Kee. Generic spin model for the honeycomb iridates beyond the kitaev limit. Phys. Rev. Lett., 112:077204, Feb 2014
2014
-
[62]
Beyond Kitaev physics in strong spin-orbit coupled magnets
Ioannis Rousochatzakis, Natalia B Perkins, Qiang Luo, and Hae-Young Kee. Beyond Kitaev physics in strong spin-orbit coupled magnets. Rep. Prog. Phys. , 87(2):026502, feb 2024
2024
-
[63]
An introduction to topological data analysis: fundamental and practical aspects for data scientists
Frédéric Chazal and Bertrand Michel. An introduction to topological data analysis: fundamental and practical aspects for data scientists. Frontiers in artificial intelligence, 4:667963, 2021
2021
-
[64]
k- means clustering for persistent homology
Yueqi Cao, Prudence Leung, and Anthea Monod. k- means clustering for persistent homology. Advances in Data Analysis and Classification, pages 1–25, 2024
2024
-
[65]
Efficient estimation of pauli observables by derandomization
Hsin-Yuan Huang, Richard Kueng, and John Preskill. Efficient estimation of pauli observables by derandomization. Physical review letters , 127(3):030503, 2021
2021
-
[66]
Integration k-means clustering method and elbow method for identification of the best customer profile cluster
Muhammad Ali Syakur, B Khusnul Khotimah, EMS Rochman, and Budi Dwi Satoto. Integration k-means clustering method and elbow method for identification of the best customer profile cluster. In IOP conference series: materials science and engineering, volume 336, page 012017. IOP ...
2018
-
[67]
Em algorithms for pca and spca
Sam Roweis. Em algorithms for pca and spca. Advances in neural information processing systems, 10, 1997
1997
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