def test_two_qubit_reduction(self):
"""Test mapping to qubit operator with two qubit reduction"""
mapper = ParityMapper()
qubit_conv = QubitConverter(mapper, two_qubit_reduction=True)
with self.subTest(
"Two qubit reduction ignored as no num particles given"):
qubit_op = qubit_conv.convert(self.h2_op)
self.assertEqual(qubit_op, TestQubitConverter.REF_H2_PARITY)
self.assertIsNone(qubit_conv.num_particles)
with self.subTest("Two qubit reduction, num particles given"):
qubit_op = qubit_conv.convert(self.h2_op, self.num_particles)
self.assertEqual(qubit_op,
TestQubitConverter.REF_H2_PARITY_2Q_REDUCED)
self.assertEqual(qubit_conv.num_particles, self.num_particles)
with self.subTest("convert_match()"):
qubit_op = qubit_conv.convert_match(self.h2_op)
self.assertEqual(qubit_op,
TestQubitConverter.REF_H2_PARITY_2Q_REDUCED)
self.assertEqual(qubit_conv.num_particles, self.num_particles)
with self.subTest("State is reset (Num particles lost)"):
qubit_op = qubit_conv.convert(self.h2_op)
self.assertEqual(qubit_op, TestQubitConverter.REF_H2_PARITY)
self.assertIsNone(qubit_conv.num_particles)
with self.subTest("Num particles given again"):
qubit_op = qubit_conv.convert(self.h2_op, self.num_particles)
self.assertEqual(qubit_op,
TestQubitConverter.REF_H2_PARITY_2Q_REDUCED)
with self.subTest("Set for no two qubit reduction"):
qubit_conv.two_qubit_reduction = False
self.assertFalse(qubit_conv.two_qubit_reduction)
qubit_op = qubit_conv.convert(self.h2_op)
self.assertEqual(qubit_op, TestQubitConverter.REF_H2_PARITY)
# Regression test against https://github.com/Qiskit/qiskit-nature/issues/271
with self.subTest(
"Two qubit reduction skipped when operator too small"):
qubit_conv.two_qubit_reduction = True
small_op = FermionicOp([("N_0", 1.0), ("E_1", 1.0)],
register_length=2,
display_format="sparse")
expected_op = 1.0 * (I ^ I) - 0.5 * (I ^ Z) + 0.5 * (Z ^ Z)
with contextlib.redirect_stderr(io.StringIO()) as out:
qubit_op = qubit_conv.convert(small_op,
num_particles=self.num_particles)
self.assertEqual(qubit_op, expected_op)
self.assertTrue(out.getvalue().strip().startswith(
"The original qubit operator only contains 2 qubits! "
"Skipping the requested two-qubit reduction!"))
def test_mapping_basic(self):
"""Test mapping to qubit operator"""
mapper = JordanWignerMapper()
qubit_conv = QubitConverter(mapper)
qubit_op = qubit_conv.convert(self.h2_op)
self.assertIsInstance(qubit_op, PauliSumOp)
# Note: The PauliSumOp equals, as used in the test below, use the equals of the
# SparsePauliOp which in turn uses np.allclose() to determine equality of
# coeffs. So the reference operator above will be matched on that basis so
# we don't need to worry about tiny precision changes for any reason.
self.assertEqual(qubit_op, TestQubitConverter.REF_H2_JW)
with self.subTest("Re-use test"):
qubit_op = qubit_conv.convert(self.h2_op)
self.assertEqual(qubit_op, TestQubitConverter.REF_H2_JW)
with self.subTest("convert_match()"):
qubit_op = qubit_conv.convert_match(self.h2_op)
self.assertEqual(qubit_op, TestQubitConverter.REF_H2_JW)
with self.subTest("Re-use with different mapper"):
qubit_conv.mapper = ParityMapper()
qubit_op = qubit_conv.convert(self.h2_op)
self.assertEqual(qubit_op, TestQubitConverter.REF_H2_PARITY)
with self.subTest(
"Set two qubit reduction - no effect without num particles"):
qubit_conv.two_qubit_reduction = True
qubit_op = qubit_conv.convert_match(self.h2_op)
self.assertEqual(qubit_op, TestQubitConverter.REF_H2_PARITY)
with self.subTest("Force match set num particles"):
qubit_conv.force_match(self.num_particles)
qubit_op = qubit_conv.convert_match(self.h2_op)
self.assertEqual(qubit_op,
TestQubitConverter.REF_H2_PARITY_2Q_REDUCED)