def test_backend_change(self, user_expectation):
"""Test that VQE works when backend changes."""
vqe = VQE(
ansatz=TwoLocal(rotation_blocks=["ry", "rz"],
entanglement_blocks="cz"),
optimizer=SLSQP(maxiter=2),
expectation=user_expectation,
quantum_instance=BasicAer.get_backend("statevector_simulator"),
)
result0 = vqe.compute_minimum_eigenvalue(operator=self.h2_op)
if user_expectation is not None:
with self.subTest("User expectation kept."):
self.assertEqual(vqe.expectation, user_expectation)
vqe.quantum_instance = BasicAer.get_backend("qasm_simulator")
# works also if no expectation is set, since it will be determined automatically
result1 = vqe.compute_minimum_eigenvalue(operator=self.h2_op)
if user_expectation is not None:
with self.subTest(
"Change backend with user expectation, it is kept."):
self.assertEqual(vqe.expectation, user_expectation)
with self.subTest("Check results."):
self.assertEqual(len(result0.optimal_point),
len(result1.optimal_point))
def test_reuse(self):
"""Test re-using a VQE algorithm instance."""
vqe = VQE()
with self.subTest(msg='assert running empty raises AlgorithmError'):
with self.assertRaises(AlgorithmError):
_ = vqe.run()
var_form = TwoLocal(rotation_blocks=['ry', 'rz'],
entanglement_blocks='cz')
vqe.var_form = var_form
with self.subTest(msg='assert missing operator raises AlgorithmError'):
with self.assertRaises(AlgorithmError):
_ = vqe.run()
vqe.operator = self.h2_op
with self.subTest(msg='assert missing backend raises AlgorithmError'):
with self.assertRaises(AlgorithmError):
_ = vqe.run()
vqe.quantum_instance = self.statevector_simulator
with self.subTest(msg='assert VQE works once all info is available'):
result = vqe.run()
self.assertAlmostEqual(result.eigenvalue.real,
self.h2_energy,
places=5)
operator = PrimitiveOp(
np.array([[1, 0, 0, 0], [0, -1, 0, 0], [0, 0, 2, 0], [0, 0, 0,
3]]))
with self.subTest(msg='assert minimum eigensolver interface works'):
result = vqe.compute_minimum_eigenvalue(operator)
self.assertAlmostEqual(result.eigenvalue.real, -1.0, places=5)
def test_reuse(self):
"""Test re-using a VQE algorithm instance."""
vqe = VQE()
with self.subTest(msg="assert running empty raises AlgorithmError"):
with self.assertRaises(AlgorithmError):
_ = vqe.compute_minimum_eigenvalue(operator=self.h2_op)
ansatz = TwoLocal(rotation_blocks=["ry", "rz"],
entanglement_blocks="cz")
vqe.ansatz = ansatz
with self.subTest(msg="assert missing operator raises AlgorithmError"):
with self.assertRaises(AlgorithmError):
_ = vqe.compute_minimum_eigenvalue(operator=self.h2_op)
vqe.expectation = MatrixExpectation()
vqe.quantum_instance = self.statevector_simulator
with self.subTest(msg="assert VQE works once all info is available"):
result = vqe.compute_minimum_eigenvalue(operator=self.h2_op)
self.assertAlmostEqual(result.eigenvalue.real,
self.h2_energy,
places=5)
operator = PrimitiveOp(
np.array([[1, 0, 0, 0], [0, -1, 0, 0], [0, 0, 2, 0], [0, 0, 0,
3]]))
with self.subTest(msg="assert minimum eigensolver interface works"):
result = vqe.compute_minimum_eigenvalue(operator=operator)
self.assertAlmostEqual(result.eigenvalue.real, -1.0, places=5)
def test_backend_change(self, user_expectation):
"""Test that VQE works when backend changes."""
vqe = VQE(
var_form=TwoLocal(rotation_blocks=['ry', 'rz'],
entanglement_blocks='cz'),
optimizer=SLSQP(maxiter=2),
expectation=user_expectation,
quantum_instance=BasicAer.get_backend('statevector_simulator'))
result0 = vqe.compute_minimum_eigenvalue(operator=self.h2_op)
if user_expectation is not None:
with self.subTest('User expectation kept.'):
self.assertEqual(vqe.expectation, user_expectation)
else:
with self.subTest('Expectation created.'):
self.assertIsInstance(vqe.expectation, ExpectationBase)
try:
vqe.quantum_instance = BasicAer.get_backend('qasm_simulator')
except Exception as ex: # pylint: disable=broad-except
self.fail("Failed to change backend. Error: '{}'".format(str(ex)))
return
result1 = vqe.compute_minimum_eigenvalue(operator=self.h2_op)
if user_expectation is not None:
with self.subTest(
'Change backend with user expectation, it is kept.'):
self.assertEqual(vqe.expectation, user_expectation)
else:
with self.subTest(
'Change backend without user expectation, one created.'):
self.assertIsInstance(vqe.expectation, ExpectationBase)
with self.subTest('Check results.'):
self.assertEqual(len(result0.optimal_point),
len(result1.optimal_point))