def test_pauli_decomposition_3_qubit(measurement):
a1 = cirq.NamedQubit('a1')
a2 = cirq.NamedQubit('a2')
a3 = cirq.NamedQubit('a3')
for qubits in [[a1, a2, a3], [a3, a1, a2], [a2, a3, a1]]:
decomp = pauli_decomposition(measurement, qubits)
assert np.allclose(measurement, decomp.matrix(qubits))
def test_pauli_decomposition_measurement_from_vectors(vector, expected_str):
a1 = cirq.NamedQubit('a1')
a2 = cirq.NamedQubit('a2')
col = np.sqrt(0.5) * np.array(vector).reshape(4,1)
measurement = col.dot(col.T.conj())
decomp = pauli_decomposition(measurement, [a1, a2])
assert f"{decomp:.3f}" == expected_str
def test_pauli_decomposition_wrong_inputs():
a1 = cirq.NamedQubit('a1')
a2 = cirq.NamedQubit('a2')
H_not_2d = [[[0.5+0.j, 0. +0.5j],
[0. -0.5j, 0.5+0.j]]]
H_not_square = [[0.5+0.j, 0. +0.5j],
[0. -0.5j]]
H_good = [[0.5+0.j, 0. +0.5j],
[0. -0.5j, 0.5+0.j]]
with pytest.raises(ValueError, match='pauli_decomposition expects a 2-d square matrix.'):
pauli_decomposition(H_not_2d, [a1])
with pytest.raises(ValueError, match='pauli_decomposition expects a 2-d square matrix.'):
pauli_decomposition(H_not_square, [a1])
with pytest.raises(ValueError, match=re.escape('pauli_decomposition: Expect that size_of_matrix==pow(2, number_of_qubits). In your case 2!=pow(2, 2).')):
pauli_decomposition(H_good, [a1, a2])
def test_pauli_decomposition_1_qubit(measurement):
a1 = cirq.NamedQubit('a1')
decomp = pauli_decomposition(measurement, [a1])
assert np.allclose(measurement, decomp.matrix([a1]))