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237, 238, 239, 275, 280, 283 ], [ 240, 241, 242, 243, 278, 288 ], [ 244, 245, 246, 247, 276 ] ] }, "distance": { "d": 12, "X": { "value": 12, "confidence": "upper_bound", "witness": [ 60, 61, 72, 73, 80, 81, 112, 113, 144, 145, 204, 205 ] }, "Z": { "value": 12, "confidence": "upper_bound", "witness": [ 88, 89, 100, 101, 104, 105, 108, 109, 216, 217, 244, 245 ] } }, "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 [[62,10,6]] twisted-torus BB code (arXiv:2503.03827) entry, using a sparse independent-row presentation of its checks: n' = 4n + m_X + m_Z = 300, k' = 2k = 20, check weight w' = w+1 = 7. X/Z witnesses are the base witnesses tensored with the weight-2 [[4,2,2]] logical on the central register (weights 12/12); a 100000-trial fast-backend search (seed 5000) found nothing lighter (min weight 12). Base provenance: Twisted-torus bivariate-bicycle code from Generalized toric codes on twisted tori for quantum error correction (PRX Quantum 6, 020357, 2025). Stabilizers f(x,y)=1+x+x^-1y, g(x,y)=1+y+x^-1y^-1 on the abelian quotient group Z^2/L with twist basis a_1=[0, 31], a_2=[1, 13] (n=2|det[a_1,a_2]|=2*31). Reconstructed from the published polynomials and twist; CSS form H_X=[f|g], H_Z=[gbar|fbar].", "references": [ "arXiv:2609.37231", "arXiv:2503.03827" ], "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" }