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Tableau CNOT propagates Z forward instead of backward · case 02

A Z stabilizer on the target is not copied onto the control, so a Bell state reports +XX, +ZI instead of +XX, +ZZ.

Member previewVariant 2 · 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 0	`["+ZII", "+IZZ", "+IIZ"]`	`["+ZII", "+IZI", "+IZZ"]`	Failed

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