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], [ 196, 197, 198, 199, 247, 251, 252, 253, 261 ], [ 200, 201, 202, 203, 248, 250, 256, 257 ], [ 204, 205, 206, 207, 246, 247, 249, 250, 255 ], [ 208, 209, 210, 211, 248, 250, 255, 258 ], [ 212, 213, 214, 215, 247, 248, 249, 257 ], [ 216, 217, 218, 219, 252, 253 ], [ 220, 221, 222, 223, 251, 254 ] ] }, "distance": { "d": 16, "X": { "value": 16, "confidence": "upper_bound", "witness": [ 28, 29, 36, 37, 56, 57, 92, 93, 96, 97, 116, 117, 124, 125, 188, 189 ] }, "Z": { "value": 16, "confidence": "upper_bound", "witness": [ 24, 25, 64, 65, 132, 133, 152, 153, 156, 157, 176, 177, 188, 189, 196, 197 ] } }, "provenance": { "authors": [ "@MathysRennela" ], "construction": "Distance-amplified code: one [[4,2,2]] tensor-product amplification step (central three-term truncation of the chain-complex tensor product, arXiv:2609.37231 Eq. 1/Eq. 12-15) applied to the board's [[56,12,8]] entry, using a sparse independent-row presentation of its checks: n' = 4n + m_X + m_Z = 268, k' = 2k = 24, check weight w' = w+1 = 9. X/Z witnesses are the base witnesses tensored with the weight-2 [[4,2,2]] logical on the central register (weights 16/16); a 100000-trial fast-backend search (seed 5000) found nothing lighter (min weight 16). Base provenance: contributed via qldpc submit", "references": [ "arXiv:2609.37231" ], "date": "2026-09-30", "notes": "Constructed and packaged with the Space Bunny Alpha 1.0 model.", "model": "Space Bunny Alpha 1.0" }, "family": "distance-amplified" }