FA-90913 / Quantum circuit simulation / Member archive

Collapse renormalizes by probability instead of its square root · case 03

After measuring |+> the post-measurement amplitude is 1.414 instead of 1.0.

Member previewVariant 3 · 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 4	`{"probability": 0.196294, "state": [[-2.66218, -3.769647], [0.0, 0.0]]}`	`{"probability": 0.196294, "state": [[-0.576864, -0.81684], [0.0, 0.0]]}`	Failed

MEMBER ARCHIVE

The complete case is available to members.

This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

Member access is invitation-based. Sign in with your invited account to inspect the sources.