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 "provenance": {
  "authors": [
   "Lin, Hsiang-Ku",
   "Pryadko, Leonid P."
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  "origin": "baseline",
  "construction": "Generalized bicycle (cyclic 2BGA) code over C_20: a(x) = 1 + x^4, b(x) = 1 + x + x^2 + x^7.",
  "date": "2023-06-28",
  "references": [
   "arXiv:2306.16400",
   "arXiv:2203.17216"
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  "notes": "Parameters from the Lin-Pryadko 2BGA enumeration (arXiv:2306.16400, w=6 abelian/GB tier). Explicit polynomials reconstructed by exhaustive weight-6 GB search over C_20 with the repo research kit; distance proven exact by cutoff MILP (scipy/HiGHS). Seeded so the global frontier reflects the published state of the art (issue #52).\n\nLayout certification: a verifier-accepted honest bilayer layout (stacked 4x5 grid, 2 qubits per site, layers=2, measured interaction radius ~5.000) 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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