{
 "schema_version": "0.1",
 "name": "[[18,4,4]] twisted-torus BB code (arXiv:2503.03827)",
 "code_type": "CSS",
 "n": 18,
 "k": 4,
 "checks": {
  "X": [
   [
    0,
    1,
    4,
    9,
    11,
    13
   ],
   [
    1,
    3,
    6,
    10,
    13,
    15
   ],
   [
    2,
    4,
    7,
    11,
    14,
    16
   ],
   [
    0,
    2,
    3,
    11,
    12,
    15
   ],
   [
    4,
    6,
    8,
    13,
    16,
    17
   ],
   [
    1,
    5,
    7,
    9,
    10,
    14
   ],
   [
    2,
    5,
    6,
    14,
    15,
    17
   ],
   [
    3,
    7,
    8,
    10,
    12,
    16
   ],
   [
    0,
    5,
    8,
    9,
    12,
    17
   ]
  ],
  "Z": [
   [
    0,
    5,
    8,
    9,
    12,
    17
   ],
   [
    1,
    5,
    7,
    9,
    10,
    14
   ],
   [
    0,
    2,
    3,
    11,
    12,
    15
   ],
   [
    3,
    7,
    8,
    10,
    12,
    16
   ],
   [
    0,
    1,
    4,
    9,
    11,
    13
   ],
   [
    2,
    5,
    6,
    14,
    15,
    17
   ],
   [
    1,
    3,
    6,
    10,
    13,
    15
   ],
   [
    2,
    4,
    7,
    11,
    14,
    16
   ],
   [
    4,
    6,
    8,
    13,
    16,
    17
   ]
  ]
 },
 "distance": {
  "d": 4,
  "X": {
   "value": 4,
   "confidence": "upper_bound",
   "witness": [
    3,
    7,
    14,
    15
   ]
  },
  "Z": {
   "value": 4,
   "confidence": "upper_bound",
   "witness": [
    3,
    6,
    12,
    17
   ]
  }
 },
 "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+xy, g(x,y)=1+y+xy on the abelian quotient group Z^2/L with twist basis a_1=[0, 3], a_2=[3, 0] (n=2|det[a_1,a_2]|=2*9). 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. 2D-local layout added 2026-07-27: simulated annealing over qubit-to-site assignments on a unit-spaced triangular grid (1 layer, capacity 1 per site per layer); measured interaction radius 3.464102 (single-layer); same code, same check matrices.",
  "origin": "baseline",
  "novelty": "known_parameters"
 },
 "family": "bivariate-bicycle",
 "locality": {
  "coordinates": [
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   ],
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  "interaction_radius": 3.4641016151377544,
  "layers": 1
 }
}