def test_bell_split(self):
"""Test the result of a two qubit bell state split by one measurement"""
# Set test circuit
self.circuit = ReferenceCircuits.bell()
# Execute
result = super().test_run_circuit()
actual = result.get_statevector_tree()
initial = actual['value']
path_0 = actual['path_0']['value']
path_1 = actual['path_1']['value']
prob_0 = actual['path_0_probability']
prob_1 = actual['path_1_probability']
# initial (before measurement) state is 1/sqrt(2)|00> + 1/sqrt(2)|11>, up to a global phase
self.assertAlmostEqual((initial[0]), 1 / math.sqrt(2))
self.assertAlmostEqual((initial[3]), 1 / math.sqrt(2))
self.assertAlmostEqual((prob_0), 1 / 2)
self.assertAlmostEqual((prob_1), 1 / 2)
self.assertEqual(initial[1], 0)
self.assertEqual(initial[2], 0)
# path 0 state is |00>, up to a global phase
self.assertAlmostEqual((path_0[0]), 1)
self.assertEqual(path_0[1], 0)
self.assertEqual(path_0[2], 0)
self.assertEqual(path_0[3], 0)
# path 1 state is |11>, up to a global phase
self.assertAlmostEqual((path_1[3]), 1)
self.assertEqual(path_1[0], 0)
self.assertEqual(path_1[1], 0)
self.assertEqual(path_1[2], 0)
def test_measure_collapse(self):
"""Test final measurement collapses statevector"""
# Set test circuit
self.circuit = ReferenceCircuits.bell()
# Execute
result = super().test_run_circuit()
actual = result.get_statevector(self.circuit)
# The final state should be EITHER |00> OR |11>
diff_00 = np.linalg.norm(np.array([1, 0, 0, 0]) - actual) ** 2
diff_11 = np.linalg.norm(np.array([0, 0, 0, 1]) - actual) ** 2
success = np.allclose([diff_00, diff_11], [0, 2]) or np.allclose([diff_00, diff_11], [2, 0])
# state is 1/sqrt(2)|00> + 1/sqrt(2)|11>, up to a global phase
self.assertTrue(success)
