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[[64,33,2]] d =
n
64
k
33
d
2
kd²/n
2.062
w
8
X/Z
1
g
0.0206
r
3.1623
layers
2
swaps
38

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Distance

X/Z asymmetry 1 · d_X = 2, d_Z = 2 · w_X = 8, w_Z = 8 (max(d_X,d_Z)/min(d_X,d_Z); each side carries its own earned tier: = certified exact, ≤ witness upper bound)
d_X 2 · witness weight 2 (claimed upper_bound)
witness operator (support, 2 qubits)
[11, 13]
d_Z 2 · witness weight 2 (claimed upper_bound)
witness operator (support, 2 qubits)
[37, 55]
certificate exact, d = 2 · scipy/HiGHS MILP
X: no logical < 2 exists; Z: no logical < 2 exists

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 8 · H_Z 8
qubit degrees H_X 4 · H_Z 4
trapping sets H_X (1,4)×64 (2,0)×64 (3,4)×1440 (smallest syndrome weight at each size, connected sets of up to 3 qubits)
full (size, syndrome weight): count census for H_X
(1,4): 64 (2,0): 64 (2,4): 256 (2,6): 128 (3,4): 1440 (3,6): 1536 (3,8): 768
trapping sets H_Z (1,4)×64 (2,0)×48 (3,0)×128 (smallest syndrome weight at each size, connected sets of up to 3 qubits)
full (size, syndrome weight): count census for H_Z
(1,4): 64 (2,0): 48 (2,4): 352 (3,0): 128 (3,4): 2112 (3,8): 448
witness diameter X 2.0 · Z 1.4142 (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)

Verified 2D layout

as measured by the verifier: every check drawn over the submitted coordinates; the interaction radius is the longest dashed pair
layout contributed by @dorakingx · Simulated annealing over site assignments on an integer grid with the repo's own research/local2d/fold_layout.search_layout (max-diameter objective, several bounding boxes and seeds); single layer at radius 4 tried first, then two layers at 7. Radius and per-site occupancy re-measured with the verifier's rule. · 2026-10-02
r = 3.162
X checkZ checkqubit site (32)2 qubits stacked (2 layers)dashed: the pair setting the interaction radiushover a check to isolate its qubits; click to pin — repeated clicks cycle through overlapping checks; click empty space to release
routing cost 38 nearest-neighbor SWAPs per round in total, at most 2 for one check (heuristic: MST lower bound on the layout, with one lattice step = the minimum qubit spacing 1; not a rank)

Construction & provenance

authors @MathysRennela
provenance submitted through the challenge
novelty novelty not audited
construction 2BGA (arXiv:2306.16400) on SmallGroup(32,5), from github.com/QEC-pages/2BGA-codes @ 403d194c3f98f0cadc236aecbc4a8b6139ccf23c, nonabelian.zip, diswtnonabelian_wt8wtL4_order32_k33.txt, line 1. nonidentity supports a=[2, 3, 7], b=[3, 4, 11].
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 bilayer (computed from the layout)
weight class weight ≤ 8 (computed)

How this code was found

the research note submitted with this code · raw markdown · all notes

[[64,33,2]] — two-block group-algebra code on SmallGroup(32,5)

Direction & hypothesis

Target: unrestricted weight-8 frontier for hackathon issue #1155. Reconstruct a published weight-8 2BGA code absent from the local board. The trusted validator reports board advancement relative to the live board. Efficiency kd²/n = 2.06.

What was searched

Scraped GitHub for downloadable parity-check matrix artifacts and parameter tables. From github.com/QEC-pages/2BGA-codes @ 403d194c3f98f0cadc236aecbc4a8b6139ccf23c, nonabelian.zip, diswtnonabelian_wt8wtL4_order32_k33.txt, line 1. This row is SmallGroup(32,5) with nonidentity GAP supports a=[2, 3, 7], b=[3, 4, 11]. 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=33), 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 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(32,5), 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=[2, 3, 7], b=[3, 4, 11] 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 = 64 - rank(HX) - rank(HZ) = 33. 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 32 (max weight 8) · Z-checks 32 (max weight 8)
H_X (32 checks, sparse supports)
[0, 2, 21, 31, 32, 34, 35, 42] [0, 1, 2, 16, 33, 38, 39, 48] [0, 2, 28, 29, 32, 34, 35, 42] [3, 10, 28, 29, 32, 34, 35, 42] [1, 4, 11, 16, 36, 43, 45, 54] [5, 8, 12, 26, 37, 44, 46, 55] [0, 2, 6, 7, 33, 38, 39, 48] [3, 6, 7, 10, 33, 38, 39, 48] [4, 8, 11, 26, 40, 49, 51, 58] [5, 9, 12, 27, 41, 50, 52, 59] [3, 10, 21, 31, 32, 34, 35, 42] [4, 6, 7, 11, 36, 43, 45, 54] [5, 12, 17, 19, 37, 44, 46, 55] [6, 7, 13, 22, 36, 43, 45, 54] [14, 17, 19, 23, 37, 44, 46, 55] [9, 15, 24, 27, 47, 56, 57, 62] [1, 3, 10, 16, 33, 38, 39, 48] [4, 11, 17, 19, 40, 49, 51, 58] [5, 12, 18, 20, 41, 50, 52, 59] [13, 17, 19, 22, 40, 49, 51, 58] [14, 18, 20, 23, 41, 50, 52, 59] [15, 21, 24, 31, 53, 60, 61, 63] [1, 13, 16, 22, 36, 43, 45, 54] [8, 14, 23, 26, 37, 44, 46, 55] [15, 18, 20, 24, 47, 56, 57, 62] [18, 20, 25, 30, 47, 56, 57, 62] [8, 13, 22, 26, 40, 49, 51, 58] [9, 14, 23, 27, 41, 50, 52, 59] [15, 24, 28, 29, 53, 60, 61, 63] [25, 28, 29, 30, 53, 60, 61, 63] [9, 25, 27, 30, 47, 56, 57, 62] [21, 25, 30, 31, 53, 60, 61, 63]
H_Z (32 checks, sparse supports)
[0, 2, 3, 10, 32, 33, 34, 38] [1, 6, 7, 16, 33, 36, 48, 54] [0, 2, 3, 10, 32, 33, 34, 38] [0, 2, 3, 10, 35, 39, 42, 48] [4, 11, 13, 22, 36, 40, 43, 49] [5, 12, 14, 23, 37, 41, 44, 50] [1, 6, 7, 16, 38, 39, 43, 45] [1, 6, 7, 16, 38, 39, 43, 45] [8, 17, 19, 26, 37, 40, 55, 58] [9, 18, 20, 27, 41, 47, 59, 62] [0, 2, 3, 10, 35, 39, 42, 48] [4, 11, 13, 22, 36, 40, 43, 49] [5, 12, 14, 23, 37, 41, 44, 50] [4, 11, 13, 22, 45, 51, 54, 58] [5, 12, 14, 23, 46, 52, 55, 59] [15, 24, 25, 30, 47, 53, 56, 60] [1, 6, 7, 16, 33, 36, 48, 54] [8, 17, 19, 26, 44, 46, 49, 51] [9, 18, 20, 27, 50, 52, 56, 57] [8, 17, 19, 26, 44, 46, 49, 51] [9, 18, 20, 27, 50, 52, 56, 57] [21, 28, 29, 31, 32, 42, 53, 63] [4, 11, 13, 22, 45, 51, 54, 58] [5, 12, 14, 23, 46, 52, 55, 59] [15, 24, 25, 30, 47, 53, 56, 60] [15, 24, 25, 30, 57, 61, 62, 63] [8, 17, 19, 26, 37, 40, 55, 58] [9, 18, 20, 27, 41, 47, 59, 62] [21, 28, 29, 31, 34, 35, 60, 61] [21, 28, 29, 31, 34, 35, 60, 61] [15, 24, 25, 30, 57, 61, 62, 63] [21, 28, 29, 31, 32, 42, 53, 63]
Code ID 64-33-2 · download JSON · raw on GitHub