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Tableau Hadamard skips the Y sign flip · case 04

H S H on |0> reports stabilizer +Y instead of -Y.

Member previewVariant 4 · 3 implementations · 7 checks per implementation

Case contract

Input [n, gates] with gates h, s, x, z (["g", q]) and cx (["cx", c, t]). Track the n stabilizer generators of |0...0> (initially Z on each qubit) under the Aaronson-Gottesman update rules and return them as signed strings such as "+XX", character q describing qubit q.

Why this case matters

Stabilizer simulators verify Clifford circuits and error-correction encoders; a phase-bit rule error yields wrong syndromes.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
regression: random clifford 4	`["+XZY", "+ZYI", "-IYX"]`	`["-XZY", "+ZYI", "-IYX"]`	Failed

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