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All instances / Heisenberg

Heisenberg square 8x8, open

Exact energy and best values (rules §6)

exact (stochastic) -0.6190371(2) SSE QMC
Sandvik (2026) · sign-problem-free QMC, exact within its error bar
best variational -0.619034(6) VMC (2D RNN)
Moss et al. (2025) · 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
open
energies
5

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
-0.6190371exact (stochastic) 0 1.7e-7 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
-0.619034best variational 0 5.8e-6 2.20e-2 5.6e-5 VMC (2D RNN)
peer reviewed
Moss et al. (2025) mschuylermoss/HeisenbergRNN 2025
-0.619033tied with best variational at 2σ 1.5e-6 3.0e-6 n/a n/a PEPS
peer reviewed
Liu et al. (2016) 2016
-0.619025tied with best variational at 2σ 9.5e-6 5.0e-6 n/a n/a VMC (minGRU)
preprint
Merali et al. (2026) ParallelScan-RNNs/PSR-NQS 2026
-0.619013 2.1e-5 2.0e-6 n/a n/a PEPS
peer reviewed
Liu et al. (2016) 2016

How these numbers were read

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

-0.6190371(2), SSE QMC

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

Reported as. E0/N_b = 0.3537355(1) (magnitude, per bond, N_b = 112), L = 8, open

Table 2, "SSE data for L x L systems with open boundary conditions. The ground state energy is normalized by the number of interaction bonds N_b = 2(L^2 - L)", row L = 8. Printed as a magnitude; E/N = -(E0/N_b) N_b / N = -0.61903712 in S.S units, Pauli total = 4 N E/N. The L = 6 value agrees with the exact-diagonalization row on square_36_O to 3.3e-7 (2 sigma), and L = 10 and 16 reproduce the rows QMBL already quotes from this paper via arXiv:2605.13807.

-0.619034(6), 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. -0.619034469127655 +/- 0.0000057981170573067555 per site (S.S), Var(E/N) = 3.361816141023155e-7

github.com/mschuylermoss/HeisenbergRNN, commit 29bf62ac28 (2025-02-24, 'reproduce figures'), Square/final_plotting/final_data/final_energy_data_plotting.pkl: ['open']['rate=0.475']['scale=4'], L = 8; the authors' best run, the lowest of the s = 2 and 4 training schedules (s = 4, r = 0.475). Plotted as a point in Fig. 12(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.

-0.619033(3), PEPS

Checked 2026-09-15 · source text of arXiv:1611.09467 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. -0.619033(3)

TABLE II, row D=10, column L=8: -0.619033(3). | Same per-site S.S convention as above row; no rescale needed.

-0.619025(5), VMC (minGRU)

Checked 2026-10-27 · arXiv:2605.13807: arXiv:2605.13807v1 (only version; no journal reference on 2026-10-27): pypdf layout text sources/2605.13807.txt read locally, checked against Table 6 of the arXiv HTML sources/2605.13807.html; no LLM transcription; single reading

Reported as. -0.619025(5)

TABLE VI, row N = 8^2 (line 683 of sources/2605.13807.txt) | energy per site in S.S units, J = 1, open boundaries; the same table row prints the QMC value equal to the instance's stored SSE row

-0.619013(2), PEPS

Checked 2026-09-15 · source text of arXiv:1611.09467 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. -0.619013(2)

TABLE II, row D=8, column L=8: -0.619013(2). This value is not among the 8 cells present in the delivered harvest (which mismatched Table I's D=8 bond-dimension row for 16/24/100-site lattices instead) but is read directly from the source text of Table II, the table the harvester's caption field actually names for this instance. | Table II's own thermodynamic-limit row (D=8 column, L=infinity: -0.66977(25)) and its exact/QMC comparison row confirm the same per-site S.S convention as the instance's exact_per_site (-0.619037125); no rescale needed.

Coverage

Newest published number here: 2026.

This instance as data

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