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All instances / Heisenberg

Heisenberg square 14x14

Exact energy and best values (rules §6)

exact (stochastic) -0.67023225(2) SSE QMC
Sandvik (2026) · sign-problem-free QMC, exact within its error bar
best variational -0.67014(2) 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
196
boundary
periodic
energies
7

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
-0.67023225exact (stochastic) 0 2.0e-8 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
-0.67014best variational 0 2.1e-5 2.83e+0 2.0e-3 VMC (2D RNN)
peer reviewed
Moss et al. (2025) mschuylermoss/HeisenbergRNN 2025
-0.668346 1.8e-3 7.7e-6 2.21e+1 1.6e-2 VMC (Gutzwiller)
VarBench reference run
Wu et al. (2024) run script 2024
-0.66381 6.3e-3 1.0e-5 6.37e+1 4.6e-2 VMC (RBM)
VarBench reference run
Wu et al. (2024) run script 2024
-0.66256 7.6e-3 1.0e-5 6.67e+1 4.8e-2 VMC (Jastrow)
VarBench reference run
Wu et al. (2024) run script 2024
-0.6586622 1.1e-2 n/a 1.28e+2 9.4e-2 DMRG
VarBench reference run
Wu et al. (2024) run script 2024

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
-0.6703092 n/a 5.0e-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.

-0.6703092(5), 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; single reading

Reported as. -0.6703092(5)

Table III (Appendix H), row L=14, column 'RNN zero-variance E/N' | more negative than the instance's currently listed variational record (-0.6683456632653061, 'VMC with fermions'); the paper's own note that zero-variance extrapolation is not a strict bound applies here too

-0.67023225(2), SSE QMC

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

Reported as. e0 = -0.67023225(2) per spin (S.S), L = 14, 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 = 14. Pauli total = 4 N e0. The L = 6 value agrees with the exact-diagonalization row on square_36_P to 1.6e-8.

-0.67014(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. -0.6701383006816007 +/- 0.00002145833623584729 per site (S.S), Var(E/N) = 0.00000460460194010677

github.com/mschuylermoss/HeisenbergRNN, commit 29bf62ac28 (2025-02-24, 'reproduce figures'), Square/final_plotting/final_data/final_energy_data_plotting.pkl: ['periodic']['rate=0.25']['scale=4'], L = 14; the lowest of the ten training schedules (s = 4, r = 0.25). 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.

-0.668346(8), VMC (Gutzwiller)

Checked 2026-09-29 · VarBench snapshot 390a21e (vendor/varbench) and full upstream history (varbench-history, git log --follow on the file, every version); varbench/methods ed31bb0 run script and program read as text; no output log or result file exists in the methods repo for any Heisenberg row

Reported as. | -523.983 | 0.006 | 22.07 | 196 | 0 | VMC with fermions (flux+neel+Jastrow) | [code](https://github.com/varbench/methods/blob/main/scripts/Heisenberg/square_196_P/vmc_gutzwiller.sh) |

vmc_gutzwiller inputs: 2x2 supercell x '7 0 0 7' = 14x14 periodic spin torus, nelup = neldo = 98 (Sz = 0), jperp = 1, uvv = 0.25 (H = sum S.S), pi-flux + Neel field + spin Jastrow (iesspin=32); binned error (ratio 1.31). Stored = 4N x <H>/N. 1.479 above Sandvik's SSE. Entered 32046ef (2022-02-15, F. Ferrari), never changed; linked d186176 (2024-07-30).

-0.66381(1), VMC (RBM)

Checked 2026-09-29 · VarBench snapshot 390a21e (vendor/varbench) and full upstream history (varbench-history, git log --follow on the file, every version); varbench/methods ed31bb0 run script and program read as text; no output log or result file exists in the methods repo for any Heisenberg row

Reported as. | -520.4234 | 0.0079 | 63.70537 | 196 | 0 | RBM (alpha = 1) | [code](https://github.com/varbench/methods/blob/main/scripts/Heisenberg/square_196_P/vmc_rbm.sh) |

scripts/Heisenberg/square_196_P/vmc_rbm.sh: 'python3 vmc.py --ham heis --boundary peri --sign mars --ham_dim 2 --L 14 --zero_mag --net rbm --seed 123 --show_progress' -> 14x14 square lattice, periodic (nk.graph.Grid); NetKet Heisenberg J = 1 in Pauli form with Marshall sign rule (a sublattice rotation on a bipartite lattice, spectrum unchanged); Sz = 0 (total_sz=0, MetropolisExchange); real float32 RBM, alpha = 1 (nk.models.RBM, log_cosh); 10^4 SR steps; final estimate over 2^20 samples (vmc.py lines 268-269). sigma/sqrt(Var/2^20) = 1.014: the stored sigma is the error of that final estimate. 5.0387 above Sandvik's SSE -525.462084(16). History: entered 10f5c12 (2022-07-11, Dian Wu) as -517.807 | 0.0096 | 94.5612 | RBM (alpha = 1); af1d48f (2022-09-01, 'Add Jastrow baseline'): energy -517.807 -> -520.4234; sigma 0.0096 -> 0.0079; variance 94.5612 -> 63.70537; linked 5047bfd (2024-07-30). The value change sits in af1d48f, titled 'Add Jastrow baseline' (a re-run: lower energy and variance). Program files postdate the value (scripts added to varbench/methods 2024-07-30); they document the settings after the run.

-0.66256(1), VMC (Jastrow)

Checked 2026-09-29 · VarBench snapshot 390a21e (vendor/varbench) and full upstream history (varbench-history, git log --follow on the file, every version); varbench/methods ed31bb0 run script and program read as text; no output log or result file exists in the methods repo for any Heisenberg row

Reported as. | -519.4475 | 0.0081 | 66.74661 | 196 | 0 | Jastrow baseline | [code](https://github.com/varbench/methods/blob/main/scripts/Heisenberg/square_196_P/vmc_jastrow.sh) |

scripts/Heisenberg/square_196_P/vmc_jastrow.sh: 'python3 vmc.py --ham heis --boundary peri --sign mars --ham_dim 2 --L 14 --zero_mag --net jas --seed 123 --show_progress' -> 14x14 square lattice, periodic (nk.graph.Grid); NetKet Heisenberg J = 1 in Pauli form with Marshall sign rule (a sublattice rotation on a bipartite lattice, spectrum unchanged); Sz = 0 (total_sz=0, MetropolisExchange); real float32 Jastrow (nk.models.Jastrow); 10^4 SR steps; final estimate over 2^20 samples (vmc.py lines 268-269). sigma/sqrt(Var/2^20) = 1.015: the stored sigma is the error of that final estimate. 6.0146 above Sandvik's SSE -525.462084(16). History: entered af1d48f (2022-09-01, Dian Wu) as -519.4475 | 0.0081 | 66.74661 | Jastrow baseline; linked fdb4bfb (2024-07-30). Program files postdate the value (scripts added to varbench/methods 2024-07-30); they document the settings after the run.

-0.6586622, DMRG

Checked 2026-09-29 · VarBench snapshot 390a21e (vendor/varbench) and full upstream history (varbench-history, git log --follow on the file, every version); varbench/methods ed31bb0 run script and program read as text; no output log or result file exists in the methods repo for any Heisenberg row

Reported as. | -516.3911695223306 | | 127.79517553787447 | 100 | 0 | DMRG (bond dimension = 512) | [code](https://github.com/varbench/methods/blob/main/scripts/Heisenberg/square_196_P/dmrg.sh) |

dmrg.sh: heisenberg_2d.jl --peri --L 14 --zero_mag --max_B 512: 14x14 torus, Pauli, J = 1, Sz = 0, 50 sweeps at D = 512. 9.071 above Sandvik's SSE (1.7%). The DOF cell (VarBench 100, typed by hand in c85080f) is already corrected to 196 on the row (ruling 2026-09-21), v_score recomputed; the VarBench snapshot still prints 100. Entered c85080f (2022-09-03, Dian Wu), never changed; linked 2024-07-19.

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): 2 papers read, 1 of them with an energy on this page.

This instance as data

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