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 "provenance": {
  "authors": [
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  "model": "Claude Opus 5",
  "novelty": "known_parameters",
  "origin": "submission",
  "date": "2026-09-21",
  "construction": "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.",
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  "contributed_by": {
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   "date": "2026-10-02",
   "method": "Simulated annealing over site assignments on an integer grid with the repo's own research/local2d/fold_layout.search_layout (max-diameter objective, several bounding boxes and seeds); single layer at radius 4 tried first, then two layers at 7. Radius and per-site occupancy re-measured with the verifier's rule."
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