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 "name": "[[42,8,3]] generalized bicycle code",
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 "provenance": {
  "authors": [
   "Wang, Renren",
   "Pryadko, Leonid P."
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  "origin": "baseline",
  "construction": "Generalized bicycle code, circulant size 21, a(x) = 1 + x^3 + x^6 + x^12, b(x) = 1 + x^7.",
  "date": "2022-03-31",
  "references": [
   "arXiv:2203.17216"
  ],
  "notes": "Distance d=3 from arXiv:2203.17216; witness here is a decoder-found logical operator of that weight (upper bound).\n\nLayout certification: a verifier-accepted honest bilayer layout (stacked 3x7 grid, 2 qubits per site, layers=2, measured interaction radius ~6.325) was found by @mathysrennela (Aug 2026). It earns the code the local-2d-bilayer class and makes the site's geometric efficiency g = 4kd^2/(n rho^2 r^4) computable. Code authorship unchanged; layout credit to @mathysrennela."
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  "rounds": 3,
  "stim_version": "1.16.0",
  "notes": "Interleaved two-block extraction (Bravyi et al. arXiv:2308.07915 Table 5 style): joint reset and measurement layers, 7 data CX layers per round; X-check term slots [2, 4, 6, 3, 1, 5], Z-check term slots [3, 2, 0, 4, 5, 1] over terms A_0..A_3, B_0..B_1; terms recovered from H alone by a commuting permutation decomposition. Order screened by RIS among the 576 slot assignments satisfying the overlap-parity criterion (first one tried); the claim then survived 2 seeds x 1000 RIS trials per basis and an observable-constrained seeded BP+OSD search over symmetric seeds, whose lightest undetected logical fault set is weight 3 in both bases.",
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