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[[6,5,1]] d ≤
n
6
k
5
d
1
kd²/n
0.833
w
6
X/Z
2

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Distance

X/Z asymmetry 2 · d_X ≤ 1, d_Z ≤ 2 · w_X = 6, w_Z = 0 (max(d_X,d_Z)/min(d_X,d_Z); each side carries its own earned tier: = certified exact, ≤ witness upper bound)
d_X 1 · witness weight 1 (claimed upper_bound)
witness operator (support, 1 qubits)
[1]
d_Z 2 · witness weight 2 (claimed upper_bound)
witness operator (support, 2 qubits)
[0, 1]
certificate none yet · distance stands as a self-certified upper bound (d ≤)

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 acyclic · H_Z acyclic (shortest cycle of each side’s Tanner graph; longer is friendlier to belief propagation)
check weights H_X 6 · H_Z 0
qubit degrees H_X 1 · H_Z 0
trapping sets H_X (1,1)×6 (2,0)×15 (3,1)×20 (smallest syndrome weight at each size, connected sets of up to 3 qubits)
full (size, syndrome weight): count census for H_X
(1,1): 6 (2,0): 15 (3,1): 20
trapping sets H_Z (1,0)×6 (smallest syndrome weight at each size, connected sets of up to 3 qubits)
full (size, syndrome weight): count census for H_Z
(1,0): 6

Construction & provenance

authors @MathysRennela
provenance submitted through the challenge
novelty novelty not audited
construction C-DELETE-CHECK b1 from 6-4-2.json
model Beam 1.0 (claimed, not verified)
date 2026-10-19
family other (a tag, not a ranking)
locality unrestricted (computed from the layout)
weight class weight ≤ 6 (computed)

How this code was found

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

[[6,5,1]] C-DELETE-CHECK b1 from 6-4-2.json

Direction & hypothesis

Board-advancing code found by the priced construction calculus. Operation: C-DELETE-CHECK applied to a board entry, raising k / lowering check weight while keeping a witness-backed distance. Rule used: C-DELETE-CHECK.

What was searched

A single deletion move on an existing board code, validated by the trusted gate.

Evidence trail

Distance witnesses: X=[0], Z=[0, 1]. The gate's refutation search found no lighter logical.

Dead ends

None recorded for this candidate.

Tools

Model: Beam 1.0. The local verdict is verify/validate_candidate.py.

Reproduction

Reconstruct the parent board code, delete the named check, and recompute n, k, and the witness-backed distance. The resulting checks are the submitted ones.

Parity checks

X-checks 1 (max weight 6) · Z-checks 0 (max weight 0)
H_X (1 checks, sparse supports)
[0, 1, 2, 3, 4, 5]
H_Z (0 checks, sparse supports)
Code ID 6-5-1 · download JSON · raw on GitHub