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All instances / Hubbard

Hubbard rectangular 8x16, U = 8, n = 0.875, t12 (t2 = -0.2)

Record

-0.7419 E/site

Transformer backflow (MARCH)

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

The Hamiltonian

H = −t1 ∑⟨ij⟩,σ (c†iσcjσ + h.c.) −t2 ∑⟨⟨ij⟩⟩,σ (c†iσcjσ + h.c.) + U ∑i ni↑ni↓

t1 = 1, t2 = -0.2, U = 8, N↑ = N↓ = 56 on 128 sites.

This instance is a t12 variant with a next-nearest-neighbour hopping t2, written as in VarBench's Eq. (S6). t2 is the t′ of the sources' H = −t ∑⟨ij⟩ − t′ ∑⟨⟨ij⟩⟩ + U ∑ ni↑ni↓. The couplings are those each source prints (see the rows).

lattice
rectangular-8x16
sites
128
boundary
periodic
Nf
56
U
8
t1
1
t2
-0.2
energies
5

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 (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/sitedistance to recordσVar(E)V-score methodsourceyear
-0.7419record 0 n/a n/a n/a Transformer backflow (MARCH)
peer reviewed
Gu et al. (2026) 2026
-0.741 9.0e-4 n/a n/a n/a Tensor backflow (NNN backflow, direct optimization, 1 Lanczos step)
peer reviewed
Liang (2025) 2025
-0.7406 1.3e-3 n/a n/a n/a Tensor backflow (NN backflow, direct optimization, 1 Lanczos step)
peer reviewed
Liang (2025) 2025
-0.7359 6.0e-3 n/a n/a n/a Tensor backflow (NNN backflow, direct optimization)
peer reviewed
Liang (2025) 2025
-0.7354 6.5e-3 n/a n/a n/a Tensor backflow (NN backflow, direct optimization)
peer reviewed
Liang (2025) 2025

How these numbers were read

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

-0.7419, Transformer backflow (MARCH)

Checked 2026-10-22 · source text of arXiv:2507.02644 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. −0.7419

Supplementary Table 5, row 16 × 8, t' = -0.2; dl/gu-si.txt line 195; no error bar | Energy per site in units of t. PBC per the Supplementary Table 5 caption ('Raw data for the energies of Hubbard model under PBC'); U = 8 and hole doping 1/8 per the main text (Fig. 4 caption: 'U = 8 and hole doping δ = 1/8 under PBC'; the t' = -0.2 study: 'Lx × 8 with Lx ranging from 8 to 32, with t' = -0.2 and δ = 1/8'). H has -t' sum_<<ij>>, so t2 = t'. The 16 x 4 and 16 x 16 values at t' = 0 equal the arXiv text's -0.76298 and -0.75630 to the printed digits. No error bar printed. Version read: journal Supplementary Information (41467_2026_74028_MOESM1_ESM.pdf); the arXiv text has no raw-data table.

-0.741, Tensor backflow (NNN backflow, direct optimization, 1...

Checked 2026-10-22 · source text of arXiv:2507.01856 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. −0.7410

Table V, row 8 × 16, t' = -0.2, NNN backflow; dl/liang-prb.txt line 493, column Ep=1; no error bar | Energy per site in units of t at n = 0.875, U = 8, t' = -0.2 (Table V caption: 'n = 0.875 and U = 8'; Table VI column 'n, U, t′ = 0.875, 8, −0.2'). PBC: the 8 x 16 NNN Ep = 1 value -0.7410 and the 12 x 12 U_UHF = 4 Ep = 1 value -0.7420 equal Table II's PBC rows. Ep = 0 is the tensor-backflow state, Ep = 1 the same state after one Lanczos step; both are variational. No error bar printed. Version read: Phys. Rev. B 113, 155121 (publisher PDF); arXiv:2507.01856v4 (sources/2507.01856.txt) prints the same numbers.

-0.7406, Tensor backflow (NN backflow, direct optimization, 1...

Checked 2026-10-22 · source text of arXiv:2507.01856 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. −0.7406

Table V, row 8 × 16, t' = -0.2, NN backflow; dl/liang-prb.txt line 492, column Ep=1; no error bar | Energy per site in units of t at n = 0.875, U = 8, t' = -0.2 (Table V caption: 'n = 0.875 and U = 8'; Table VI column 'n, U, t′ = 0.875, 8, −0.2'). PBC: the 8 x 16 NNN Ep = 1 value -0.7410 and the 12 x 12 U_UHF = 4 Ep = 1 value -0.7420 equal Table II's PBC rows. Ep = 0 is the tensor-backflow state, Ep = 1 the same state after one Lanczos step; both are variational. No error bar printed. Version read: Phys. Rev. B 113, 155121 (publisher PDF); arXiv:2507.01856v4 (sources/2507.01856.txt) prints the same numbers.

-0.7359, Tensor backflow (NNN backflow, direct optimization)

Checked 2026-10-22 · source text of arXiv:2507.01856 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. −0.7359

Table V, row 8 × 16, t' = -0.2, NNN backflow; dl/liang-prb.txt line 493, column Ep=0; no error bar | Energy per site in units of t at n = 0.875, U = 8, t' = -0.2 (Table V caption: 'n = 0.875 and U = 8'; Table VI column 'n, U, t′ = 0.875, 8, −0.2'). PBC: the 8 x 16 NNN Ep = 1 value -0.7410 and the 12 x 12 U_UHF = 4 Ep = 1 value -0.7420 equal Table II's PBC rows. Ep = 0 is the tensor-backflow state, Ep = 1 the same state after one Lanczos step; both are variational. No error bar printed. Version read: Phys. Rev. B 113, 155121 (publisher PDF); arXiv:2507.01856v4 (sources/2507.01856.txt) prints the same numbers.

-0.7354, Tensor backflow (NN backflow, direct optimization)

Checked 2026-10-22 · source text of arXiv:2507.01856 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. −0.7354

Table V, row 8 × 16, t' = -0.2, NN backflow; dl/liang-prb.txt line 492, column Ep=0; no error bar | Energy per site in units of t at n = 0.875, U = 8, t' = -0.2 (Table V caption: 'n = 0.875 and U = 8'; Table VI column 'n, U, t′ = 0.875, 8, −0.2'). PBC: the 8 x 16 NNN Ep = 1 value -0.7410 and the 12 x 12 U_UHF = 4 Ep = 1 value -0.7420 equal Table II's PBC rows. Ep = 0 is the tensor-backflow state, Ep = 1 the same state after one Lanczos step; both are variational. No error bar printed. Version read: Phys. Rev. B 113, 155121 (publisher PDF); arXiv:2507.01856v4 (sources/2507.01856.txt) prints the same numbers.

Coverage

Newest published number here: 2026.

This instance as data

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