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All instances / Heisenberg

Heisenberg square 8x8

Exact energy and best values (rules §6)

exact (stochastic) -0.67349005(2) SSE QMC
Sandvik (2026) · sign-problem-free QMC, exact within its error bar
best variational -0.6735 VMC (HQT)
Guo et al. (2026) · the lowest unflagged variational energy, a strict variational bound

Energies as E/N (S.S). Classes are different claims and are not ranked against each other.

The Hamiltonian

H = ∑⟨ij⟩ σi·σj

Nearest-neighbour Heisenberg antiferromagnet, J = 1, written with Pauli matrices.

lattice
square
sites
64
boundary
periodic
energies
6

Stored as a total energy; quoted here as E/N (S.S), which is what the papers report (how the conversion works).

Every published energy

Grouped by what the number is. The exact energy comes first where there is one; in every other group the lowest unflagged energy is its best value, and each row's distance is to that best (rules §6).

Numerically exact (1)

Exact diagonalization, an exact solution, or sign-problem-free QMC where that is established. An exact energy is shown first, before the best of each other class. QMC is exact only within its error bar, which it must state, and reads exact (stochastic); an exact diagonalization outranks it. For a diagonalization resolved by symmetry sector only the ground state's sector is listed; the lowest energies of the other sectors are the instance's spectrum, in its JSON, and are not shown as the exact energy.

E/N (S.S)distance to class bestσVar(E)V-score methodsourcecodeyearcomment
-0.67349005exact (stochastic) 0 2.0e-8 n/a n/a SSE QMC
peer reviewed
Sandvik (2026) 2026

Strict variational upper bounds (4)

Energies that a variational state reached (VMC, DMRG and MPS at finite bond dimension, PEPS, NQS, VQE). Each is an upper bound on the ground-state energy.

E/N (S.S)distance to class bestσVar(E)V-score methodsourcecodeyearcomment
-0.6735best variational 0 n/a n/a n/a VMC (HQT)
peer reviewed
Guo et al. (2026) uses NetKet 2026
-0.673482 <1e-4 3.0e-6 n/a n/a VMC (RBM)
peer reviewed
Chen et al. (2022) 2022
-0.67346tied with best variational at 2σ <1e-4 2.3e-5 3.51e-1 7.5e-4 VMC (2D RNN)
peer reviewed
Moss et al. (2025) mschuylermoss/HeisenbergRNN 2025
-0.673434 <1e-4 n/a n/a n/a VMC (ViT)
preprint
Golubev et al. (2026) uses NetKet 2026

Extrapolations (1)

Zero-variance or bond-dimension extrapolations. These are not bounds: no ansatz reached the number.

E/N (S.S)distance to class bestσVar(E)V-score methodsourcecodeyearcomment
-0.6735047 n/a 2.0e-7 n/a n/a VMC (2D RNN)
below exact by > 2σ peer reviewed
Moss et al. (2025) mschuylermoss/HeisenbergRNN 2025

How these numbers were read

Where each number below was read, and how it was checked.

-0.6735047(2), VMC (2D RNN)

Checked 2026-09-15 · source text of arXiv:2502.17144 read locally (arXiv HTML or pypdf layout text); value copied from the harvested cell and the text, no LLM transcription of numbers; adversarial re-read: confirmed

Reported as. -0.6735047(2)

Table III, row L=8, column 'RNN, zero-variance E/N' | Same row's quoted QMC[76] value (-0.67349002(4)) matches instance exact_per_site -0.67349005 to displayed precision.

-0.6735, VMC (HQT)

Checked 2026-09-15 · source text of arXiv:2607.00398 read locally (arXiv HTML or pypdf layout text); value copied from the harvested cell and the text, no LLM transcription of numbers; adversarial re-read: confirmed

Reported as. -0.6735

Table 2 (Summary of Phase Diagram Scan, 8x8), row J2/J1=0.00: E/N=-0.6735, sigma^2_{E/N}=0.0005, Phase=Neel | J2/J1=0.00 is the unfrustrated NN Heisenberg AFM, matching the candidate's empty-params 'Heisenberg' model. Value -0.6735 vs instance exact_per_site -0.67349005 matches to printed precision; paper states the 8x8 lattice is a 'torus' with 'Periodic Boundary Conditions (PBC)' throughout, matching the P-boundary candidate. | variance reported as 0.0005, not stored: convention not verified

-0.67349005(2), SSE QMC

Checked 2026-09-15 · arXiv HTML parsed locally, one value per table cell; no LLM transcription

Reported as. e0 = -0.67349005(2) per spin (S.S), L = 8, periodic

Table 1, "Results for different system sizes computed at inverse temperature beta/L = 64 for L > 30 and averaged over beta/L = 32 and beta/L = 64 simulations for L <= 30", column e0, row L = 8. Pauli total = 4 N e0. The L = 6 value agrees with the exact-diagonalization row on square_36_P to 1.6e-8.

-0.673482(3), VMC (RBM)

Checked 2026-09-15 · source text of arXiv:2206.14307 read locally (arXiv HTML or pypdf layout text); value copied from the harvested cell and the text, no LLM transcription of numbers; single reading

Reported as. -0.673482(3)

Table 3, row '8x8', column 'Energy(RBM)'; text: 'we collect 2x10^5 samples to calculate the average and statistical error' | same instance as QMC row above; slightly above exact_per_site as expected for a variational bound

-0.67346(2), VMC (2D RNN)

Checked 2026-09-16 · authors' data release read locally (pickle via numpy), values copied by key, no transcription; the file is committed as sources/2502.17144-repo-final_energy_data.json and reproduces the four values Table V prints

Reported as. -0.6734647750854492 +/- 0.000023129494476360125 per site (S.S), Var(E/N) = 0.000005349735147319734

github.com/mschuylermoss/HeisenbergRNN, commit 29bf62ac28 (2025-02-24, 'reproduce figures'), Square/final_plotting/final_data/final_energy_data_plotting.pkl: ['periodic']['rate=0.475']['scale=4'], L = 8; the lowest of the ten training schedules (s = 4, r = 0.475). Plotted as a point in Fig. 3(a), not printed in the paper; Table III prints the zero-variance extrapolation over the s >= 1 runs at this L, carried on this instance as an `extrapolated` row. Variance is Var(H)/N^2 in S.S units (see script header); total = var x N^2 x 16.

-0.673434, VMC (ViT)

Checked 2026-09-15 · source text of arXiv:2606.04558 read locally (arXiv HTML or pypdf layout text); value copied from the harvested cell and the text, no LLM transcription of numbers; single reading

Reported as. -0.673434

Table I, row J2=0.00, column '8×8, ViT (this work)' | Table I value is already printed per-site (not total): e.g. 6×6 ED at J2=0.50 prints -0.503809, exactly matching catalog J1J2/square_36_P_0.5 exact_per_site -0.5038096539; the J2=0.00 quoted QMC column value -0.67349005 [29] exactly equals catalog Heisenberg/square_64_P exact_per_site -0.67349005 (and -0.67155266 [29] equals Heisenberg/square_100_P exact_per_site -0.67155266) — confirms direct S·S per-site match, no Pauli conversion needed.

Coverage

Newest published number here: 2026.

This instance as data

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