QMBLthe quantum many-body leaderboard

All instances / Hubbard

Hubbard square 4x4, U = 8, n = 0.875

Record

-0.74177(5) E/site

HFPS (GCNN)

Chen et al. (2026) · lowest unflagged energy published, a strict variational bound (rules §6)

The Hamiltonian

H = −t ∑⟨ij⟩,σ (c†iσcjσ + h.c.) + U ∑i ni↑ni↓

t = 1, U = 8, N↑ = N↓ = 7 on 16 sites.

lattice
square
sites
16
boundary
periodic
Nf
7
U
8
energies
2

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

Every published energy

Grouped by what the number is. On a solved instance the exact energy is the record; otherwise the lowest unflagged energy of any group holds it (rules §6).

Strict variational upper bounds (2)

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/sitedistance to recordσVar(E)V-score methodsourceyear
-0.74177record 0 5.0e-5 n/a n/a HFPS (GCNN)
peer reviewed
Chen et al. (2026) 2026
-0.7409 8.7e-4 1.0e-4 n/a n/a HFDS (full hidden sub-matrix)
peer reviewed
Moreno et al. (2022) 2022

How these numbers were read

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

-0.74177(5), HFPS (GCNN)

Checked 2026-10-22 · source text of arXiv:2507.10705 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. -0.74177(5)

TABLE IV, 4x4 row; sources/2507.10705.txt line 968; version read: arXiv v1 (sources/2507.10705.txt); PNAS copy not reached (Cloudflare 403, 2026-10-16) | Eq. (15): H = -t sum_<ij> + U sum n_up n_dn, t = 1, t' = 0, periodic; all tables per site (E/Nsite).

-0.7409(1), HFDS (full hidden sub-matrix)

Checked 2026-10-22 · source text of arXiv:2111.10420 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. -0.7409(1)

Appendix H Table IV, L=4, column "Energy per site HFDS (PBC-PBC)"; sources/2111.10420.txt line 1253; version read: arXiv:2111.10420v2 text, Appendix H (sources/2111.10420.txt); the PNAS SI (Cloudflare 403 on 2026-10-16) was read for this paper's earlier rows on 2026-09-29 | Eq. (1): H = -sum t_ij (c+c + h.c.) + U sum n_up n_dn, t = 1. Tables I-III print totals on the 4x4 torus (ED -17.698 on 16 sites); Tables IV and V print 'energy per site'. The rounded U of the tables (0.6, 2.15, 3.6, 7.75) are the grid 10^(k/9): QMBL's ED at U = 0.59948425 gives -19.47476333 and at 2.15443469 (n = 1/2) -18.40532088, the printed ED values, against -19.47434179 at U = 0.6 and -18.40534078 at U = 2.1544 (checks/hubbard-u-labels/results-2026-10-16/, run_fermions.mjs).

Coverage

Newest published number here: 2026.

This instance as data

JSON · source file on GitHub · add a result · open an issue about this instance