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  ]
 },
 "distance": {
  "d": 6,
  "X": {
   "value": 8,
   "confidence": "upper_bound",
   "witness": [
    48,
    49,
    56,
    57,
    152,
    153,
    176,
    177
   ]
  },
  "Z": {
   "value": 6,
   "confidence": "upper_bound",
   "witness": [
    64,
    65,
    132,
    133,
    188,
    189
   ]
  }
 },
 "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 [[54,21,3]] entry, using a sparse independent-row presentation of its checks: n' = 4n + m_X + m_Z = 249, k' = 2k = 42, 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 8/6); a 100000-trial fast-backend search (seed 5000) found nothing lighter (min weight 6). Base provenance: Check deletion from the board entry [[54,20,4]] (codes/54-20-4.json): row 2 of H_X removed. Dropping one stabiliser generator frees one logical qubit 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"
}