wai-quantum 0.3.28: the dense state vector at any angle, the same bits threaded or not #147

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dcharlot merged 1 commit from wai-quantum-sv into main 2026-10-05 05:06:49 -04:00

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2026-10-04

Transaction Science

wai-quantum 0.3.28: the dense state vector at any angle, the same bits threaded or not ...

The byte-exact simulator is fixed-point and dyadic by design. quantum_sv is
the general state vector for everything else (arbitrary rotations, sqrt W,
fSim, random unitaries), and the ground truth approximate methods are
measured against, up to about 30 qubits.

- Split real and imaginary arrays; qubit 0 most significant, as in the
  tensor networks.
- Kernels: unrolled one- and two-qubit, general k-qubit, and a diagonal
  fast path.
- Fusion around multi-qubit gates: pending one-qubit gates join the next
  multi-qubit gate on their qubit, trailing ones the last, and above width 2
  adjacent multi-qubit gates merge. Each move only crosses gates on other
  qubits.
- Threads, with no unsafe code: block-aligned slices, and for gates on the
  top qubits a split at the top target bit, or into four quarters for
  adjacent pairs.
- Every path computes each amplitude through one row sum in one order, so
  threading never changes a bit. The native-vs-WASI pin caught a path whose
  sum ran in a different order; the fix is the shared row_dot, and a test
  now forces 1/2/3/8/32 threads and demands identical states (falsified by
  reversing one kernel's sum).
- Reductions (norm, Pauli expectations, sorted-uniform sampling) are summed
  in fixed chunks.

gates: Gate moves here from quantum_tn (re-exported there), with the
standard gates by name: H, X, Y, Z, S, T, sqrt X/Y/W, RX/RY/RZ, phase, CX,
CZ, SWAP, iSWAP, CPhase, RZZ, fSim.

Checked:
- final states of random circuits on 8, 12 and 16 qubits agree with an
  independent simulator to 2e-16 at fusion widths 0, 2 and 4;
- tensor-network amplitudes equal the state vector's to 1e-12 on 18 qubits
  (tests/tn_vs_sv.rs);
- a 26-qubit, depth-20, 770-gate circuit runs in about 9 s at width 2, in
  double precision.

CLI: wai-quantum sv --file CIRCUIT.jsonl [--fuse --top --sample --expect
--json]; tn shares its circuit reader. Byte-identical natively and under
wasm32-wasip2.

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

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