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All instances / Heisenberg

Heisenberg square 16x16, open

Exact energy and best values (rules §6)

exact (stochastic) -0.6435317(2) SSE QMC
Sandvik (2026) · sign-problem-free QMC, exact within its error bar
best variational -0.643522(7) 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
256
boundary
open
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
-0.6435317exact (stochastic) 0 1.9e-7 n/a n/a SSE QMC
peer reviewed
Sandvik (2026) 2026

Strict variational upper bounds (5)

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
-0.643522best variational 0 7.2e-6 5.43e-1 3.2e-4 VMC (2D RNN)
peer reviewed
Moss et al. (2025) mschuylermoss/HeisenbergRNN 2025
-0.643504tied with best variational at 2σ 1.8e-5 3.0e-6 n/a n/a VMC (minGRU)
preprint
Merali et al. (2026) ParallelScan-RNNs/PSR-NQS 2026
-0.643448 7.4e-5 1.0e-6 n/a n/a VMC (NAQS)
peer reviewed
Sharir et al. (2019) uses FlowKet 2019
-0.643396 1.3e-4 6.0e-6 n/a n/a VMC (minGRU)
preprint
Merali et al. (2026) ParallelScan-RNNs/PSR-NQS 2026
-0.643391 1.3e-4 3.0e-6 n/a n/a PEPS
peer reviewed
Liu et al. (2017) 2017

How these numbers were read

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

-0.6435317(2), SSE QMC

Checked 2026-09-14 · arXiv HTML parsed locally from a benchmark comparison table, no LLM transcription

Reported as. -0.6435317 (+/- 2e-7) per site in S.S units

Read from Table 2 of arXiv:2605.13807 (2D Heisenberg, square lattice, OBC, E/N in S.S units), parsed from the arXiv HTML. Column "QMC [49]" = arXiv:2601.20189.

-0.643522(7), 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. -0.6435218453407288 +/- 0.0000071965624241340895 per site (S.S), Var(E/N) = 5.179051072445873e-7

github.com/mschuylermoss/HeisenbergRNN, commit 29bf62ac28 (2025-02-24, 'reproduce figures'), Square/final_plotting/final_data/final_energy_data_plotting.pkl: ['open']['rate=0.25']['scale=2'], L = 16; the authors' best run, the lowest of the s = 2 and 4 training schedules (s = 2, r = 0.25). 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.

-0.643504(3), VMC (minGRU)

Checked 2026-09-14 · arXiv HTML parsed locally from a benchmark comparison table, no LLM transcription

Reported as. -0.643504 (+/- 0.000003) per site in S.S units

Read from Table 2 of arXiv:2605.13807 (2D Heisenberg, square lattice, OBC, E/N in S.S units), parsed from the arXiv HTML. The citing paper's own result; 29 GPU-days on a single L40S.

-0.643448(1), VMC (NAQS)

Checked 2026-09-15 · source text of arXiv:1902.04057 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. -0.643448(1)

Table II, 16x16 row, 'NAQS' column | Same table/instance as PEPS row; matches exact_per_site scale.

-0.643396(6), VMC (minGRU)

Checked 2026-09-15 · source text of arXiv:2605.13807 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. -0.643396(6)

TABLE VI, N=16^2 row | per-site convention confirmed via row's own QMC quote -0.6435317(2)

-0.643391(3), PEPS

Checked 2026-09-14 · arXiv HTML parsed locally from a benchmark comparison table, no LLM transcription

Reported as. -0.643391 (+/- 0.000003) per site in S.S units

Read from Table 2 of arXiv:2605.13807 (2D Heisenberg, square lattice, OBC, E/N in S.S units), parsed from the arXiv HTML. Column "PEPS [33]".

Coverage

Newest published number here: 2026. Literature last checked 2026-09-15 (table harvest of cached arXiv sources (match_tables.mjs --all), every matched paper read for this instance): 3 papers read, 1 of them with an energy on this page.

This instance as data

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