FA-90917 / Quantum circuit simulation / Member archive

Collapse reports unnormalized branch mass as probability · case 02

An input 2|00> + 2|11> reports probability 4 for outcome 0 of qubit 1.

Member previewVariant 2 · 3 implementations · 7 checks per implementation

Case contract

Input [n, amps, q, outcome]; measure qubit q (0 = LSB) of the possibly unnormalized state. Return {"probability": p, "state": post} with p normalized by the total squared norm and the post-measurement state renormalized to unit norm with the other branch zeroed; values rounded to 6 decimals. Return "impossible" when p < 1e-12.

Why this case matters

Mid-circuit measurement and collapse drive dynamic circuits; wrong renormalization breaks every later probability.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
regression: random collapse 3	`{"probability": 2.568824, "state": [[0.0, 0.0], [0.38933, 0.23834], [0.0, 0.0], [-0.184058, 0.179067], [0.0, 0.0], [-0.286382, 0.06676], [0.0, 0.0], [0.616439, 0.509123]]}`	`{"probability": 0.422407, "state": [[0.0, 0.0], [0.38933, 0.23834], [0.0, 0.0], [-0.184058, 0.179067], [0.0, 0.0], [-0.286382, 0.06676], [0.0, 0.0], [0.616439, 0.509123]]}`	Failed

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