def test_probabilities_w(self):
"""Test probabilities method with W state"""
psi = (
Statevector.from_label("001")
+ Statevector.from_label("010")
+ Statevector.from_label("100")
) / np.sqrt(3)
state = DensityMatrix(psi)
# 3-qubit qargs
target = np.array([0, 1 / 3, 1 / 3, 0, 1 / 3, 0, 0, 0])
for qargs in [[0, 1, 2], [2, 1, 0], [1, 2, 0], [1, 0, 2]]:
with self.subTest(msg=f"P({qargs})"):
probs = state.probabilities(qargs)
self.assertTrue(np.allclose(probs, target))
# 2-qubit qargs
target = np.array([1 / 3, 1 / 3, 1 / 3, 0])
for qargs in [[0, 1], [2, 1], [1, 2], [1, 2]]:
with self.subTest(msg=f"P({qargs})"):
probs = state.probabilities(qargs)
self.assertTrue(np.allclose(probs, target))
# 1-qubit qargs
target = np.array([2 / 3, 1 / 3])
for qargs in [[0], [1], [2]]:
with self.subTest(msg=f"P({qargs})"):
probs = state.probabilities(qargs)
self.assertTrue(np.allclose(probs, target))
def test_probabilities_ghz(self):
"""Test probabilities method for GHZ state"""
psi = (Statevector.from_label('000') +
Statevector.from_label('111')) / np.sqrt(2)
state = DensityMatrix(psi)
# 3-qubit qargs
target = np.array([0.5, 0, 0, 0, 0, 0, 0, 0.5])
for qargs in [[0, 1, 2], [2, 1, 0], [1, 2, 0], [1, 0, 2]]:
with self.subTest(msg='P({})'.format(qargs)):
probs = state.probabilities(qargs)
self.assertTrue(np.allclose(probs, target))
# 2-qubit qargs
target = np.array([0.5, 0, 0, 0.5])
for qargs in [[0, 1], [2, 1], [1, 2], [1, 2]]:
with self.subTest(msg='P({})'.format(qargs)):
probs = state.probabilities(qargs)
self.assertTrue(np.allclose(probs, target))
# 1-qubit qargs
target = np.array([0.5, 0.5])
for qargs in [[0], [1], [2]]:
with self.subTest(msg='P({})'.format(qargs)):
probs = state.probabilities(qargs)
self.assertTrue(np.allclose(probs, target))
