FAILURE MAP
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FA-90846 / Quantum circuit simulation / Open access

Statevector Pauli-Y applies the conjugate phases · case 01

After Y on |0> the simulator reports amplitude -i on |1> instead of +i, and interference with later H gates flips outcome probabilities.

Verified by executionVariant 1 · 7 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The Y kernel writes i*b to the |0> slot and -i*a to the |1> slot, which is the matrix of -Y; the simulated statevector carries the wrong sign on every Y application.

THE FAILURE

The Y kernel writes i*b to the |0> slot and -i*a to the |1> slot, which is the matrix of -Y; the simulated statevector carries the wrong sign on every Y application.

Unsuccessful approach: The attempted fix only corrects the |1> slot to i*a and keeps +i*b on |0>, which is not unitary-consistent with Y.

Case contract

Input [n, gates]; start in |0...0>, apply gates h,x,y,z,s,sdg,t (["g", q]) and cx,cz,swap (["g", a, b]) with qubit 0 as the least significant bit of the basis index; return the statevector as [re, im] pairs rounded to 6 decimals.

Why this case matters

Statevector simulators underpin circuit unit tests; a gate-kernel slip silently corrupts every downstream amplitude.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
import math
import cmath
N = 1
observations = []
def solve(x):
    n, gates = x
    dim = 1 << n
    st = [0j] * dim
    st[0] = 1 + 0j
    r = 1 / math.sqrt(2)
    for g in gates:
        op = g[0]
        if op in ('h', 'x', 'y', 'z', 's', 'sdg', 't'):
            m = 1 << g[1]
            for i in range(dim):
                if i & m:
                    continue
                a, b = st[i], st[i | m]
                if op == 'h':
                    st[i], st[i | m] = (a + b) * r, (a - b) * r
                elif op == 'x':
                    st[i], st[i | m] = b, a
                elif op == 'y':
                    st[i], st[i | m] = 1j * b, -1j * a
                elif op == 'z':
                    st[i | m] = -b
                elif op == 's':
                    st[i | m] = 1j * b
                elif op == 'sdg':
                    st[i | m] = -1j * b
                else:
                    st[i | m] = b * cmath.exp(1j * math.pi / 4)
        elif op == 'cx':
            c, t = 1 << g[1], 1 << g[2]
            for i in range(dim):
                if i & c and not i & t:
                    st[i], st[i | t] = st[i | t], st[i]
        elif op == 'cz':
            both = (1 << g[1]) | (1 << g[2])
            for i in range(dim):
                if i & both == both:
                    st[i] = -st[i]
        elif op == 'swap':
            a, b = 1 << g[1], 1 << g[2]
            for i in range(dim):
                if i & a and not i & b:
                    j = (i ^ a) | b
                    st[i], st[j] = st[j], st[i]
    return [[round(v.real, 6) + 0.0, round(v.imag, 6) + 0.0] for v in st]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['regression: y on ground state', [1, [['y', 0]]], [[0.0, 0.0], [0.0, 1.0]]], ['regression: y after x', [1, [['x', 0], ['y', 0]]], [[0.0, -1.0], [0.0, 0.0]]], ['regression: random circuit 15', [2, [['cx', 1, 0], ['z', 0], ['cz', 1, 0], ['h', 1], ['h', 0], ['y', 1], ['h', 1]]], [[0.0, 0.0], [0.0, 0.0], [0.0, -0.707107], [0.0, -0.707107]]], ['control: empty circuit on two qubits', [2, []], [[1.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0]]], ['control: bell pair', [2, [['h', 0], ['cx', 0, 1]]], [[0.707107, 0.0], [0.0, 0.0], [0.0, 0.0], [0.707107, 0.0]]], ['control: ghz three qubits', [3, [['h', 0], ['cx', 0, 1], ['cx', 1, 2]]], [[0.707107, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.707107, 0.0]]], ['control: cx with control on high qubit', [2, [['x', 1], ['cx', 1, 0]]], [[0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [1.0, 0.0]]]], [['regression: random circuit 2', [3, [['z', 0], ['sdg', 1], ['cx', 1, 0], ['cz', 0, 1], ['cx', 2, 0], ['y', 0], ['z', 2]]], [[0.0, 0.0], [0.0, 1.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0]]], ['regression: random circuit 4', [2, [['cx', 0, 1], ['cz', 0, 1], ['h', 1], ['x', 1], ['y', 0], ['swap', 0, 1]]], [[0.0, 0.0], [0.0, 0.0], [0.0, 0.707107], [0.0, 0.707107]]], ['repair check: random circuit 17', [3, [['swap', 2, 0], ['t', 2], ['y', 1], ['sdg', 0], ['y', 1], ['cz', 0, 1], ['z', 2]]], [[1.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0]]], ['control: swap moves excitation', [3, [['x', 0], ['swap', 0, 2]]], [[0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [1.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0]]], ['control: t after h', [1, [['h', 0], ['t', 0]]], [[0.707107, 0.0], [0.5, 0.5]]], ['control: sdg after h', [2, [['h', 1], ['sdg', 1]]], [[0.707107, 0.0], [0.0, 0.0], [0.0, -0.707107], [0.0, 0.0]]], ['control: h on excited qubit', [1, [['x', 0], ['h', 0]]], [[0.707107, 0.0], [-0.707107, 0.0]]]], [['regression: random circuit 19', [1, [['sdg', 0], ['y', 0], ['sdg', 0], ['s', 0], ['x', 0], ['z', 0], ['t', 0]]], [[0.0, 1.0], [0.0, 0.0]]], ['regression: random circuit 21', [3, [['cz', 2, 0], ['s', 0], ['cx', 1, 0], ['y', 2], ['sdg', 0], ['sdg', 2], ['cx', 0, 2]]], [[0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [1.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0]]], ['regression: y after x', [1, [['x', 0], ['y', 0]]], [[0.0, -1.0], [0.0, 0.0]]], ['control: single x on qubit 0 of three', [3, [['x', 0]]], [[0.0, 0.0], [1.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0]]], ['control: random circuit 1', [3, [['cx', 1, 2], ['cz', 2, 1]]], [[1.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0]]], ['control: random circuit 3', [2, [['x', 1], ['s', 1], ['x', 0], ['h', 0], ['s', 1], ['h', 1]]], [[-0.5, 0.0], [0.5, 0.0], [0.5, 0.0], [-0.5, 0.0]]], ['control: random circuit 5', [2, [['cx', 1, 0], ['cx', 0, 1], ['t', 1], ['h', 1]]], [[0.707107, 0.0], [0.0, 0.0], [0.707107, 0.0], [0.0, 0.0]]]], [['regression: random circuit 31', [3, [['cx', 0, 2], ['x', 2], ['y', 2]]], [[0.0, -1.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0]]], ['regression: random circuit 32', [1, [['x', 0], ['sdg', 0], ['x', 0], ['sdg', 0], ['s', 0], ['y', 0]]], [[0.0, 0.0], [1.0, 0.0]]], ['repair check: random circuit 17', [3, [['swap', 2, 0], ['t', 2], ['y', 1], ['sdg', 0], ['y', 1], ['cz', 0, 1], ['z', 2]]], [[1.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0]]], ['control: random circuit 6', [2, [['cz', 0, 1], ['cz', 0, 1], ['z', 1], ['sdg', 0], ['x', 0], ['x', 1], ['cx', 0, 1]]], [[0.0, 0.0], [1.0, 0.0], [0.0, 0.0], [0.0, 0.0]]], ['control: random circuit 7', [2, [['s', 0], ['cz', 1, 0], ['x', 1], ['cx', 1, 0], ['swap', 1, 0]]], [[0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [1.0, 0.0]]], ['control: random circuit 8', [1, [['s', 0], ['h', 0], ['s', 0]]], [[0.707107, 0.0], [0.0, 0.707107]]], ['control: random circuit 9', [1, [['z', 0], ['t', 0], ['z', 0], ['h', 0]]], [[0.707107, 0.0], [0.707107, 0.0]]]], [['regression: random circuit 39', [3, [['swap', 0, 2], ['cx', 2, 1], ['y', 2], ['z', 2], ['cx', 0, 1], ['sdg', 0], ['cx', 2, 0]]], [[0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, -1.0], [0.0, 0.0], [0.0, 0.0]]], ['regression: y on ground state', [1, [['y', 0]]], [[0.0, 0.0], [0.0, 1.0]]], ['regression: y after x', [1, [['x', 0], ['y', 0]]], [[0.0, -1.0], [0.0, 0.0]]], ['control: random circuit 10', [3, [['cz', 0, 1], ['h', 0], ['z', 0], ['cx', 0, 1], ['s', 0], ['sdg', 0]]], [[0.707107, 0.0], [0.0, 0.0], [0.0, 0.0], [-0.707107, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0]]], ['control: random circuit 11', [2, [['s', 0], ['h', 0]]], [[0.707107, 0.0], [0.707107, 0.0], [0.0, 0.0], [0.0, 0.0]]], ['control: random circuit 12', [3, [['sdg', 2], ['h', 2], ['h', 1], ['s', 0], ['z', 0], ['cx', 0, 1]]], [[0.5, 0.0], [0.0, 0.0], [0.5, 0.0], [0.0, 0.0], [0.5, 0.0], [0.0, 0.0], [0.5, 0.0], [0.0, 0.0]]], ['control: random circuit 13', [2, [['sdg', 0], ['cz', 0, 1], ['swap', 0, 1], ['cx', 1, 0]]], [[1.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0]]]]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
regression: y on ground state[[0.0, 0.0], [0.0, -1.0]][[0.0, 0.0], [0.0, 1.0]]Failed
regression: y after x[[0.0, 1.0], [0.0, 0.0]][[0.0, -1.0], [0.0, 0.0]]Failed
regression: random circuit 15[[0.0, 0.0], [0.0, 0.0], [0.0, 0.707107], [0.0, 0.707107]][[0.0, 0.0], [0.0, 0.0], [0.0, -0.707107], [0.0, -0.707107]]Failed
control: empty circuit on two qubits[[1.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0]][[1.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0]]Passed
control: bell pair[[0.707107, 0.0], [0.0, 0.0], [0.0, 0.0], [0.707107, 0.0]][[0.707107, 0.0], [0.0, 0.0], [0.0, 0.0], [0.707107, 0.0]]Passed
control: ghz three qubits[[0.707107, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.707107, 0.0]][[0.707107, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.707107, 0.0]]Passed
control: cx with control on high qubit[[0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [1.0, 0.0]][[0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [1.0, 0.0]]Passed

SHA-256 / 9ebe68fa205de75f7fc69f8a01d2fc59ef7a1aa72250556f8dda54e012ad82c4

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
import math
import cmath
N = 1
observations = []
def solve(x):
    n, gates = x
    dim = 1 << n
    st = [0j] * dim
    st[0] = 1 + 0j
    r = 1 / math.sqrt(2)
    for g in gates:
        op = g[0]
        if op in ('h', 'x', 'y', 'z', 's', 'sdg', 't'):
            m = 1 << g[1]
            for i in range(dim):
                if i & m:
                    continue
                a, b = st[i], st[i | m]
                if op == 'h':
                    st[i], st[i | m] = (a + b) * r, (a - b) * r
                elif op == 'x':
                    st[i], st[i | m] = b, a
                elif op == 'y':
                    st[i], st[i | m] = 1j * b, 1j * a
                elif op == 'z':
                    st[i | m] = -b
                elif op == 's':
                    st[i | m] = 1j * b
                elif op == 'sdg':
                    st[i | m] = -1j * b
                else:
                    st[i | m] = b * cmath.exp(1j * math.pi / 4)
        elif op == 'cx':
            c, t = 1 << g[1], 1 << g[2]
            for i in range(dim):
                if i & c and not i & t:
                    st[i], st[i | t] = st[i | t], st[i]
        elif op == 'cz':
            both = (1 << g[1]) | (1 << g[2])
            for i in range(dim):
                if i & both == both:
                    st[i] = -st[i]
        elif op == 'swap':
            a, b = 1 << g[1], 1 << g[2]
            for i in range(dim):
                if i & a and not i & b:
                    j = (i ^ a) | b
                    st[i], st[j] = st[j], st[i]
    return [[round(v.real, 6) + 0.0, round(v.imag, 6) + 0.0] for v in st]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['regression: y on ground state', [1, [['y', 0]]], [[0.0, 0.0], [0.0, 1.0]]], ['regression: y after x', [1, [['x', 0], ['y', 0]]], [[0.0, -1.0], [0.0, 0.0]]], ['regression: random circuit 15', [2, [['cx', 1, 0], ['z', 0], ['cz', 1, 0], ['h', 1], ['h', 0], ['y', 1], ['h', 1]]], [[0.0, 0.0], [0.0, 0.0], [0.0, -0.707107], [0.0, -0.707107]]], ['control: empty circuit on two qubits', [2, []], [[1.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0]]], ['control: bell pair', [2, [['h', 0], ['cx', 0, 1]]], [[0.707107, 0.0], [0.0, 0.0], [0.0, 0.0], [0.707107, 0.0]]], ['control: ghz three qubits', [3, [['h', 0], ['cx', 0, 1], ['cx', 1, 2]]], [[0.707107, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.707107, 0.0]]], ['control: cx with control on high qubit', [2, [['x', 1], ['cx', 1, 0]]], [[0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [1.0, 0.0]]]], [['regression: random circuit 2', [3, [['z', 0], ['sdg', 1], ['cx', 1, 0], ['cz', 0, 1], ['cx', 2, 0], ['y', 0], ['z', 2]]], [[0.0, 0.0], [0.0, 1.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0]]], ['regression: random circuit 4', [2, [['cx', 0, 1], ['cz', 0, 1], ['h', 1], ['x', 1], ['y', 0], ['swap', 0, 1]]], [[0.0, 0.0], [0.0, 0.0], [0.0, 0.707107], [0.0, 0.707107]]], ['repair check: random circuit 17', [3, [['swap', 2, 0], ['t', 2], ['y', 1], ['sdg', 0], ['y', 1], ['cz', 0, 1], ['z', 2]]], [[1.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0]]], ['control: swap moves excitation', [3, [['x', 0], ['swap', 0, 2]]], [[0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [1.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0]]], ['control: t after h', [1, [['h', 0], ['t', 0]]], [[0.707107, 0.0], [0.5, 0.5]]], ['control: sdg after h', [2, [['h', 1], ['sdg', 1]]], [[0.707107, 0.0], [0.0, 0.0], [0.0, -0.707107], [0.0, 0.0]]], ['control: h on excited qubit', [1, [['x', 0], ['h', 0]]], [[0.707107, 0.0], [-0.707107, 0.0]]]], [['regression: random circuit 19', [1, [['sdg', 0], ['y', 0], ['sdg', 0], ['s', 0], ['x', 0], ['z', 0], ['t', 0]]], [[0.0, 1.0], [0.0, 0.0]]], ['regression: random circuit 21', [3, [['cz', 2, 0], ['s', 0], ['cx', 1, 0], ['y', 2], ['sdg', 0], ['sdg', 2], ['cx', 0, 2]]], [[0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [1.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0]]], ['regression: y after x', [1, [['x', 0], ['y', 0]]], [[0.0, -1.0], [0.0, 0.0]]], ['control: single x on qubit 0 of three', [3, [['x', 0]]], [[0.0, 0.0], [1.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0]]], ['control: random circuit 1', [3, [['cx', 1, 2], ['cz', 2, 1]]], [[1.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0]]], ['control: random circuit 3', [2, [['x', 1], ['s', 1], ['x', 0], ['h', 0], ['s', 1], ['h', 1]]], [[-0.5, 0.0], [0.5, 0.0], [0.5, 0.0], [-0.5, 0.0]]], ['control: random circuit 5', [2, [['cx', 1, 0], ['cx', 0, 1], ['t', 1], ['h', 1]]], [[0.707107, 0.0], [0.0, 0.0], [0.707107, 0.0], [0.0, 0.0]]]], [['regression: random circuit 31', [3, [['cx', 0, 2], ['x', 2], ['y', 2]]], [[0.0, -1.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0]]], ['regression: random circuit 32', [1, [['x', 0], ['sdg', 0], ['x', 0], ['sdg', 0], ['s', 0], ['y', 0]]], [[0.0, 0.0], [1.0, 0.0]]], ['repair check: random circuit 17', [3, [['swap', 2, 0], ['t', 2], ['y', 1], ['sdg', 0], ['y', 1], ['cz', 0, 1], ['z', 2]]], [[1.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0]]], ['control: random circuit 6', [2, [['cz', 0, 1], ['cz', 0, 1], ['z', 1], ['sdg', 0], ['x', 0], ['x', 1], ['cx', 0, 1]]], [[0.0, 0.0], [1.0, 0.0], [0.0, 0.0], [0.0, 0.0]]], ['control: random circuit 7', [2, [['s', 0], ['cz', 1, 0], ['x', 1], ['cx', 1, 0], ['swap', 1, 0]]], [[0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [1.0, 0.0]]], ['control: random circuit 8', [1, [['s', 0], ['h', 0], ['s', 0]]], [[0.707107, 0.0], [0.0, 0.707107]]], ['control: random circuit 9', [1, [['z', 0], ['t', 0], ['z', 0], ['h', 0]]], [[0.707107, 0.0], [0.707107, 0.0]]]], [['regression: random circuit 39', [3, [['swap', 0, 2], ['cx', 2, 1], ['y', 2], ['z', 2], ['cx', 0, 1], ['sdg', 0], ['cx', 2, 0]]], [[0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, -1.0], [0.0, 0.0], [0.0, 0.0]]], ['regression: y on ground state', [1, [['y', 0]]], [[0.0, 0.0], [0.0, 1.0]]], ['regression: y after x', [1, [['x', 0], ['y', 0]]], [[0.0, -1.0], [0.0, 0.0]]], ['control: random circuit 10', [3, [['cz', 0, 1], ['h', 0], ['z', 0], ['cx', 0, 1], ['s', 0], ['sdg', 0]]], [[0.707107, 0.0], [0.0, 0.0], [0.0, 0.0], [-0.707107, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0]]], ['control: random circuit 11', [2, [['s', 0], ['h', 0]]], [[0.707107, 0.0], [0.707107, 0.0], [0.0, 0.0], [0.0, 0.0]]], ['control: random circuit 12', [3, [['sdg', 2], ['h', 2], ['h', 1], ['s', 0], ['z', 0], ['cx', 0, 1]]], [[0.5, 0.0], [0.0, 0.0], [0.5, 0.0], [0.0, 0.0], [0.5, 0.0], [0.0, 0.0], [0.5, 0.0], [0.0, 0.0]]], ['control: random circuit 13', [2, [['sdg', 0], ['cz', 0, 1], ['swap', 0, 1], ['cx', 1, 0]]], [[1.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0]]]]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
regression: y on ground state[[0.0, 0.0], [0.0, 1.0]][[0.0, 0.0], [0.0, 1.0]]Passed
regression: y after x[[0.0, 1.0], [0.0, 0.0]][[0.0, -1.0], [0.0, 0.0]]Failed
regression: random circuit 15[[0.0, 0.707107], [0.0, 0.707107], [0.0, 0.0], [0.0, 0.0]][[0.0, 0.0], [0.0, 0.0], [0.0, -0.707107], [0.0, -0.707107]]Failed
control: empty circuit on two qubits[[1.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0]][[1.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0]]Passed
control: bell pair[[0.707107, 0.0], [0.0, 0.0], [0.0, 0.0], [0.707107, 0.0]][[0.707107, 0.0], [0.0, 0.0], [0.0, 0.0], [0.707107, 0.0]]Passed
control: ghz three qubits[[0.707107, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.707107, 0.0]][[0.707107, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [0.707107, 0.0]]Passed
control: cx with control on high qubit[[0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [1.0, 0.0]][[0.0, 0.0], [0.0, 0.0], [0.0, 0.0], [1.0, 0.0]]Passed

SHA-256 / 0ebf1353fefc1e7bd39203a7bacb0df365b4b3de510c5c71830c211721cb54c1

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 7 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

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Verification & scope

A deterministic bounded teaching model with a stipulated toy contract; amplitudes are rounded to fixed decimals for strict JSON output. It is not a production quantum SDK and claims no standards conformance. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:51:30.423036+00:00.

Case digest / 8ce1832c825ffe6bedfb1d52c45f38e6c1debc89e8eeacda3635a9d9c047bcda