Diagnostics
computed by the verifier from the parity checks, the layout, and the stored witnesses; shown as evidence, not used for ranking
girth H_X 4 · H_Z 4 (shortest cycle of each side’s Tanner graph; longer is friendlier to belief propagation)
check weights H_X 6 · H_Z 6
qubit degrees H_X 2–4 (mean 3.0) · H_Z 2–4 (mean 3.0)
trapping sets H_X (1,2)×24 (2,0)×24 (3,0)×96 (smallest syndrome weight at each size, connected sets of up to 3 qubits)
full (size, syndrome weight): count census for H_X
(1,2): 24
(1,4): 24
(2,0): 24
(2,2): 96
(2,4): 48
(3,0): 96
(3,2): 240
(3,4): 192
(3,6): 96
trapping sets H_Z (1,2)×24 (2,0)×24 (3,0)×96 (smallest syndrome weight at each size, connected sets of up to 3 qubits)
full (size, syndrome weight): count census for H_Z
(1,2): 24
(1,4): 24
(2,0): 24
(2,2): 96
(2,4): 48
(3,0): 96
(3,2): 240
(3,4): 192
(3,6): 96
witness diameter X 2.2361 · Z 1.0 (Euclidean support diameter of the stored distance witnesses in the layout; an upper bound on the exhibited logicals’ spread, not a minimum over all logicals)
Construction & provenance
provenance submitted through the challenge
novelty novelty not audited
construction 2BGA (arXiv:2306.16400) on SmallGroup(24,2), from github.com/QEC-pages/2BGA-codes @ 403d194c3f98f0cadc236aecbc4a8b6139ccf23c, abelian.zip, diswtabelian_wt6wtL2_order24_k24.txt, line 1. nonidentity supports a=[5], b=[5, 6, 15].
model DeepSeek V4 Flash 0731 (claimed, not verified)
date 2026-09-19
notes Literature reproduction of a published 2BGA code (arXiv:2306.16400; github.com/QEC-pages/2BGA-codes @ 403d194c3f98f0cadc236aecbc4a8b6139ccf23c). Checked against the live board: not equivalent to any existing entry.
family generalized bicycle (a tag, not a ranking)
locality 2D-local single (computed from the layout)
weight class weight ≤ 6 (computed)
How this code was found
[[48,24,2]] — two-block group-algebra code on SmallGroup(24,2)
Direction & hypothesis
Target: unrestricted weight-6 frontier for hackathon issue #1155. Reconstruct a published weight-6 2BGA code absent from the local board. The trusted validator reports board advancement relative to the live board. Efficiency kd²/n = 2.00.
What was searched
Scraped GitHub for downloadable parity-check matrix artifacts and parameter tables. From github.com/QEC-pages/2BGA-codes @ 403d194c3f98f0cadc236aecbc4a8b6139ccf23c, abelian.zip, diswtabelian_wt6wtL2_order24_k24.txt, line 1. This row is SmallGroup(24,2) with nonidentity GAP supports a=[5], b=[5, 6, 15]. Reconstructed via GAP (Cayley table) and the repository's group-algebra constructor.
Evidence trail
The trusted candidate gate returned passed: true, structural verification passed (CSS, connectivity, k=24), and no lighter logical was found in the refutation search. Distance is a witness-backed upper bound d ≤ 2, not an exact certificate. The published distance (d=2) is consistent with this run.
Dead ends
None for this candidate. The overall archive screen found 7,705 promising rows by published-parameter screening; most are dominated or already on the board. This row survived the screen and the gate.
Tools
DeepSeek V4 Flash 0731 (provenance.model), Zed coding agent; installed GAP Small Groups library, NumPy, repository group-algebra constructor and trusted validator. Public artifacts fetched by immutable commit URL and treated as data. Bounded local CPU run, no paid compute.
Reproduction
Use GAP g := SmallGroup(24,2), e := Elements(g). Construct the zero-based Cayley table mul[i,j] = Position(e,e[i+1]*e[j+1])-1. The published nonidentity supports are a=[5], b=[5, 6, 15] in GAP's one-based indexing. Add identity and convert to zero-based. Build HX=[L(a)|R(b)], HZ=[R(b)^T|L(a)^T] with left/right regular representations. Verify CSS; k = 48 - rank(HX) - rank(HZ) = 24. Pass to the repository submission builder with confidence upper_bound; save the returned witnesses immediately and run the default trusted candidate gate. Do not replace the returned distance with the paper's number.
Parity checks
X-checks 24 (max weight 6) · Z-checks 24 (max weight 6)
H_X (24 checks, sparse supports)
[0, 4, 24, 28, 43, 47]
[1, 7, 25, 31, 32, 41]
[2, 10, 26, 30, 34, 39]
[3, 11, 27, 35, 36, 44]
[0, 4, 24, 28, 43, 47]
[5, 14, 24, 28, 29, 38]
[6, 15, 30, 39, 40, 46]
[1, 7, 25, 31, 32, 41]
[8, 17, 32, 37, 41, 45]
[9, 18, 25, 31, 33, 42]
[2, 10, 26, 30, 34, 39]
[3, 11, 27, 35, 36, 44]
[12, 20, 26, 34, 36, 44]
[13, 21, 27, 35, 37, 45]
[5, 14, 24, 28, 29, 38]
[6, 15, 30, 39, 40, 46]
[16, 22, 29, 38, 40, 46]
[8, 17, 32, 37, 41, 45]
[9, 18, 25, 31, 33, 42]
[19, 23, 33, 42, 43, 47]
[12, 20, 26, 34, 36, 44]
[13, 21, 27, 35, 37, 45]
[16, 22, 29, 38, 40, 46]
[19, 23, 33, 42, 43, 47]
H_Z (24 checks, sparse supports)
[0, 4, 5, 14, 24, 28]
[1, 7, 9, 18, 25, 31]
[2, 10, 12, 20, 26, 34]
[3, 11, 13, 21, 27, 35]
[0, 4, 5, 14, 24, 28]
[5, 14, 16, 22, 29, 38]
[2, 6, 10, 15, 30, 39]
[1, 7, 9, 18, 25, 31]
[1, 7, 8, 17, 32, 41]
[9, 18, 19, 23, 33, 42]
[2, 10, 12, 20, 26, 34]
[3, 11, 13, 21, 27, 35]
[3, 11, 12, 20, 36, 44]
[8, 13, 17, 21, 37, 45]
[5, 14, 16, 22, 29, 38]
[2, 6, 10, 15, 30, 39]
[6, 15, 16, 22, 40, 46]
[1, 7, 8, 17, 32, 41]
[9, 18, 19, 23, 33, 42]
[0, 4, 19, 23, 43, 47]
[3, 11, 12, 20, 36, 44]
[8, 13, 17, 21, 37, 45]
[6, 15, 16, 22, 40, 46]
[0, 4, 19, 23, 43, 47]