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   "confidence": "upper_bound",
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 "provenance": {
  "authors": [
   "@MathysRennela"
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  "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 [[40,10,4]], 2D-local bilayer layout entry, using a sparse independent-row presentation of its checks: n' = 4n + m_X + m_Z = 190, k' = 2k = 20, check weight w' = w+1 = 6. 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: Reconstructed from qecdb.org record (see provenance.references); H-field X/Z row split, k recomputed, witnesses from the kit's random search.",
  "references": [
   "arXiv:2609.37231"
  ],
  "date": "2026-09-30",
  "notes": "Constructed and packaged with the Space Bunny Alpha 1.0 model. Filed under the -b slug: the board's codes/190-20-8.json (merged in #2396, by @FarLab) is the same construction -- one [[4,2,2]] amplification of codes/40-10-4.json -- presented on a different row basis of the base checks. Both have n=190, k=20, rank(H_X)=rank(H_Z)=85 per side, the same row-weight and column-weight multisets, and verify/validate_candidate.py reports exact_duplicate_of null but wl_equivalent_of 190-20-8.json, so the two are flagged as possibly equivalent and are NOT claimed to be distinct codes; the difference is a generating-set choice, not a new construction. Replacing that entry is reserved to its listed authors (verify/check_authorship.py, issue #611), which is why this is a separate file. No 2D-local layout is claimed: the entry's name in earlier drafts said '2D-local bilayer layout' but no layout block was ever attached, and none was found here. Lifting the base's layout (codes/40-10-4.json, measured max check diameter 5.3852) through the amplification needs each base qubit's four amplifier copies on two sites, and with layers=2 (capacity 2 per site) and the required 1.0 site spacing, 8 of the 40 base sites are boxed in -- their nearest admissible second site is 2.0 away -- putting rows through them at 7.10 or more against the 7.0 local-2d-bilayer cap. The entry is therefore unrestricted, with coordinates withheld rather than shipped over the cap.",
  "model": "Space Bunny Alpha 1.0"
 },
 "family": "distance-amplified"
}