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    164,
    165
   ]
  },
  "Z": {
   "value": 8,
   "confidence": "upper_bound",
   "witness": [
    24,
    25,
    36,
    37,
    64,
    65,
    120,
    121
   ]
  }
 },
 "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 [[42,13,4]] entry, using a sparse independent-row presentation of its checks: n' = 4n + m_X + m_Z = 197, k' = 2k = 26, 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 8/8); a 100000-trial fast-backend search (seed 5000) found nothing lighter (min weight 8). Base provenance: Check deletion from the board entry [[42,11,4]] (codes/42-11-4.json): rows [12, 15] of H_Z removed. Dropping two independent stabiliser generators frees two logical qubits and cannot raise the distance.",
  "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"
}