wai-quantum 0.3.25: error correction at circuit level, sampled, modelled and decoded exactly #143

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2026-10-04

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wai-quantum 0.3.25: error correction at circuit level, sampled, modelled and decoded exactly ...

quantum_frame takes an error-correction experiment as what it is: a noisy
Clifford circuit with detectors and observables.

- parse reads the ecosystem's circuit text (resets and measurements in Z and
  X, H/S/sqrt(X)/Paulis/CX/CZ/SWAP, flip and depolarizing noise, detectors,
  observables, REPEAT), and refuses anything else rather than skipping it.
- sample is bit-packed Pauli-frame simulation, 64 shots per word, with
  geometric skipping between noise hits; reproducible from
  (circuit, shots, seed).
- error_model derives the detector error model by backward sensitivity
  propagation. It converts depolarizing channels to equivalent independent
  mechanisms exactly, XOR-merges identical ones, and refuses non-deterministic
  detectors. A graphlike mechanism stays one matching edge; otherwise it splits
  into X and Z halves, then into per-qubit parts.
- surface_code_memory generates the rotated surface-code memory experiment.

quantum_match decodes by exact minimum-weight perfect matching: Dijkstra on
integer weights, with boundary paths computed once and dominated pairs cut,
then Edmonds' blossom. memory_experiment and fit_code_model measure
P(d) = a(p/p*)^((d+1)/2): a = 0.023, p* = 0.0100 under uniform circuit
noise, and CodeFit::surface_code feeds that into a resource estimate.

Checked against an independent implementation:
- generated circuits identical byte for byte (135 configurations, d 2-15,
  1-8 rounds);
- error models identical mechanism for mechanism, to 1e-12 in probability
  (41 circuits: rotated and unrotated surface codes in both bases,
  repetition codes);
- decoded logical error rates within 1.4 standard errors on all 12 grid
  points.

tests/frame_reference.rs keeps a circuit and a model from that implementation
as fixtures. Blossom equals brute force on 3000 random graphs. A mirrored
random Clifford circuit over every gate type ties the sampler's forward rules
to the model's backward ones. Mutating the depolarizing conversion, any gate
rule on either side, the determinism check or the decomposition fails a named
test. bit_identity pins sampling, decoding and the fit natively and under
wasm32-wasip2; repro gains an in-crate exp, within an ulp.

CLI: wai-quantum qec [-d --rounds --p --shots --seed --json] | --file |
--circuit | --dem | --fit, and estimate --prefactor/--threshold for a
measured code. Byte-identical natively and under wasm32-wasip2.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

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