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 "name": "[[48,4,8]] twisted-torus BB code (arXiv:2503.03827)",
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 "n": 48,
 "k": 4,
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   "confidence": "upper_bound",
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 "provenance": {
  "authors": [
   "Zijian Liang",
   "Ke Liu",
   "Hao Song",
   "Yu-An Chen"
  ],
  "construction": "Twisted-torus bivariate-bicycle code from Generalized toric codes on twisted tori for quantum error correction (PRX Quantum 6, 020357, 2025). Stabilizers f(x,y)=1+x+x^2, g(x,y)=1+y+x^2 on the abelian quotient group Z^2/L with twist basis a_1=[0, 3], a_2=[8, 1] (n=2|det[a_1,a_2]|=2*24). Reconstructed from the published polynomials and twist; CSS form H_X=[f|g], H_Z=[gbar|fbar].",
  "references": [
   "arXiv:2503.03827"
  ],
  "date": "2025",
  "notes": "Reconstructed baseline from Liang, Liu, Song, Chen, Generalized toric codes on twisted tori for quantum error correction (PRX Quantum 6, 020357, 2025), arXiv:2503.03827. The [[n,k,d]] parameter set and stabilizer polynomials are published in that paper; this entry reproduces them. Distance is an upper bound per the paper (probabilistic for d>20); the witness is the surrogate logical of that weight. Seeded to fill a board coverage gap at this block size, not a discovery. Also, a verifier-accepted honest bilayer layout (stacked 4x6 grid, 2 qubits per site, layers=2, measured interaction radius ~5.831) was found by @mathysrennela (Aug 2026) and is shipped in this file's locality block; 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. Credit for this layout goes to @mathysrennela; code authorship remains with the paper's authors.",
  "origin": "baseline",
  "novelty": "known_parameters"
 },
 "family": "bivariate-bicycle",
 "locality": {
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 "circuit": {
  "d_circ": {
   "X": {
    "value": 8,
    "confidence": "upper_bound",
    "witness": [
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   "Z": {
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    "confidence": "upper_bound",
    "witness": [
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  "rounds": 8,
  "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 plus flag layers (2 flag qubits per check ancilla, flag CX gaps 1,4;2,5); X-check term slots [3, 2, 4, 5, 1, 6], Z-check term slots [2, 4, 3, 0, 5, 1] over terms A_0..A_2, B_0..B_2; terms recovered from H by commuting permutation decomposition; order chosen by a seeded BP+OSD search on the DEM plus RIS"
 }
}