def test_molecular_operator_consistency(self):
# Initialize H2 InteractionOperator.
n_qubits = 4
filename = os.path.join(THIS_DIRECTORY, 'data',
'H2_sto-3g_singlet_0.7414')
molecule = MolecularData(filename=filename)
molecule_interaction = molecule.get_molecular_hamiltonian()
molecule_operator = get_fermion_operator(molecule_interaction)
constant = molecule_interaction.constant
one_body_coefficients = molecule_interaction.one_body_tensor
two_body_coefficients = molecule_interaction.two_body_tensor
# Perform decomposition.
eigenvalues, one_body_squares, one_body_corrections, trunc_error = (
low_rank_two_body_decomposition(two_body_coefficients))
self.assertAlmostEqual(trunc_error, 0.)
# Build back operator constant and one-body components.
decomposed_operator = FermionOperator((), constant)
for p, q in itertools.product(range(n_qubits), repeat=2):
term = ((p, 1), (q, 0))
coefficient = (one_body_coefficients[p, q] +
one_body_corrections[p, q])
decomposed_operator += FermionOperator(term, coefficient)
# Build back two-body component.
for l in range(one_body_squares.shape[0]):
one_body_operator = FermionOperator()
for p, q in itertools.product(range(n_qubits), repeat=2):
term = ((p, 1), (q, 0))
coefficient = one_body_squares[l, p, q]
if abs(eigenvalues[l]) > 1e-6:
self.assertTrue(is_hermitian(one_body_squares[l]))
one_body_operator += FermionOperator(term, coefficient)
decomposed_operator += eigenvalues[l] * (one_body_operator**2)
# Test for consistency.
difference = normal_ordered(decomposed_operator - molecule_operator)
self.assertAlmostEqual(0., difference.induced_norm())
# Decompose with slightly negative operator that must use eigen
molecule = MolecularData(filename=filename)
molecule.two_body_integrals[0, 0, 0, 0] -= 1
eigenvalues, one_body_squares, one_body_corrections, trunc_error = (
low_rank_two_body_decomposition(two_body_coefficients))
self.assertAlmostEqual(trunc_error, 0.)
# Check for property errors
with self.assertRaises(TypeError):
eigenvalues, one_body_squares, _, trunc_error = (
low_rank_two_body_decomposition(two_body_coefficients + 0.01j,
truncation_threshold=1.,
final_rank=1))
def __init__(self,
hamiltonian: 'ops.InteractionOperator',
truncation_threshold: Optional[float] = 1e-8,
final_rank: Optional[int] = None,
spin_basis=True) -> None:
self.truncation_threshold = truncation_threshold
self.final_rank = final_rank
# Perform the low rank decomposition of two-body operator.
self.eigenvalues, self.one_body_squares, one_body_correction, _ = (
low_rank_two_body_decomposition(
hamiltonian.two_body_tensor,
truncation_threshold=self.truncation_threshold,
final_rank=self.final_rank,
spin_basis=spin_basis))
# Get scaled density-density terms and basis transformation matrices.
self.scaled_density_density_matrices = [] # type: List[numpy.ndarray]
self.basis_change_matrices = [] # type: List[numpy.ndarray]
for j in range(len(self.eigenvalues)):
density_density_matrix, basis_change_matrix = (
prepare_one_body_squared_evolution(self.one_body_squares[j]))
self.scaled_density_density_matrices.append(
numpy.real(self.eigenvalues[j] * density_density_matrix))
self.basis_change_matrices.append(basis_change_matrix)
# Get transformation matrix and orbital energies for one-body terms
one_body_coefficients = (hamiltonian.one_body_tensor +
one_body_correction)
quad_ham = ops.QuadraticHamiltonian(one_body_coefficients)
self.one_body_energies, self.one_body_basis_change_matrix, _ = (
quad_ham.diagonalizing_bogoliubov_transform())
super().__init__(hamiltonian)
def test_one_body_square_decomposition(self):
# Initialize H2 InteractionOperator.
n_qubits = 4
filename = os.path.join(THIS_DIRECTORY, 'data',
'H2_sto-3g_singlet_0.7414')
molecule = MolecularData(filename=filename)
molecule_interaction = molecule.get_molecular_hamiltonian()
get_fermion_operator(molecule_interaction)
two_body_coefficients = molecule_interaction.two_body_tensor
# Decompose.
eigenvalues, one_body_squares, _, _ = (low_rank_two_body_decomposition(
two_body_coefficients, truncation_threshold=0))
rank = eigenvalues.size
for l in range(rank):
one_body_operator = FermionOperator()
for p, q in itertools.product(range(n_qubits), repeat=2):
term = ((p, 1), (q, 0))
coefficient = one_body_squares[l, p, q]
one_body_operator += FermionOperator(term, coefficient)
one_body_squared = one_body_operator**2
# Get the squared one-body operator via one-body decomposition.
if abs(eigenvalues[l]) < 1e-6:
with self.assertRaises(ValueError):
prepare_one_body_squared_evolution(one_body_squares[l])
continue
else:
density_density_matrix, basis_transformation_matrix = (
prepare_one_body_squared_evolution(one_body_squares[l]))
two_body_operator = FermionOperator()
for p, q in itertools.product(range(n_qubits), repeat=2):
term = ((p, 1), (p, 0), (q, 1), (q, 0))
coefficient = density_density_matrix[p, q]
two_body_operator += FermionOperator(term, coefficient)
# Confirm that the rotations diagonalize the one-body squares.
hopefully_diagonal = basis_transformation_matrix.dot(
numpy.dot(
one_body_squares[l],
numpy.transpose(
numpy.conjugate(basis_transformation_matrix))))
diagonal = numpy.diag(hopefully_diagonal)
difference = hopefully_diagonal - numpy.diag(diagonal)
self.assertAlmostEqual(0., numpy.amax(numpy.absolute(difference)))
density_density_alternative = numpy.outer(diagonal, diagonal)
difference = density_density_alternative - density_density_matrix
self.assertAlmostEqual(0., numpy.amax(numpy.absolute(difference)))
# Test spectra.
one_body_squared_spectrum = eigenspectrum(one_body_squared)
two_body_spectrum = eigenspectrum(two_body_operator)
difference = two_body_spectrum - one_body_squared_spectrum
self.assertAlmostEqual(0., numpy.amax(numpy.absolute(difference)))
def test_random_operator_consistency(self):
# Initialize a random InteractionOperator and FermionOperator.
n_orbitals = 3
n_qubits = 2 * n_orbitals
random_interaction = random_interaction_operator(n_orbitals,
expand_spin=True,
real=True,
seed=8)
random_fermion = get_fermion_operator(random_interaction)
# Decompose.
eigenvalues, one_body_squares, one_body_correction, error = (
low_rank_two_body_decomposition(
random_interaction.two_body_tensor))
self.assertFalse(error)
# Build back operator constant and one-body components.
decomposed_operator = FermionOperator((), random_interaction.constant)
one_body_coefficients = (random_interaction.one_body_tensor +
one_body_correction)
for p, q in itertools.product(range(n_qubits), repeat=2):
term = ((p, 1), (q, 0))
coefficient = one_body_coefficients[p, q]
decomposed_operator += FermionOperator(term, coefficient)
# Build back two-body component.
for l in range(n_orbitals**2):
one_body_operator = FermionOperator()
for p, q in itertools.product(range(n_qubits), repeat=2):
term = ((p, 1), (q, 0))
coefficient = one_body_squares[l, p, q]
one_body_operator += FermionOperator(term, coefficient)
decomposed_operator += eigenvalues[l] * (one_body_operator**2)
# Test for consistency.
difference = normal_ordered(decomposed_operator - random_fermion)
self.assertAlmostEqual(0., difference.induced_norm())
def test_rank_reduction(self):
# Initialize H2 InteractionOperator.
n_qubits = 4
n_orbitals = 2
filename = os.path.join(THIS_DIRECTORY, 'data',
'H2_sto-3g_singlet_0.7414')
molecule = MolecularData(filename=filename)
molecule_interaction = molecule.get_molecular_hamiltonian()
fermion_operator = get_fermion_operator(molecule_interaction)
constant = molecule_interaction.constant
two_body_coefficients = molecule_interaction.two_body_tensor
# Rank reduce with threshold.
errors = []
for truncation_threshold in [1., 0.1, 0.01, 0.001]:
# Decompose with threshold.
(test_eigenvalues, one_body_squares, one_body_correction,
trunc_error) = low_rank_two_body_decomposition(
two_body_coefficients,
truncation_threshold=truncation_threshold)
# Make sure error is below truncation specification.
self.assertTrue(trunc_error > 0.)
self.assertTrue(trunc_error < truncation_threshold)
self.assertTrue(len(test_eigenvalues) < n_orbitals**2)
self.assertTrue(len(one_body_squares) == len(test_eigenvalues))
# Build back operator constant and one-body components.
decomposed_operator = FermionOperator((), constant)
one_body_coefficients = (molecule_interaction.one_body_tensor +
one_body_correction)
for p, q in itertools.product(range(n_qubits), repeat=2):
term = ((p, 1), (q, 0))
coefficient = one_body_coefficients[p, q]
decomposed_operator += FermionOperator(term, coefficient)
# Build back two-body component.
for l in range(len(test_eigenvalues)):
one_body_operator = FermionOperator()
for p, q in itertools.product(range(n_qubits), repeat=2):
term = ((p, 1), (q, 0))
coefficient = one_body_squares[l, p, q]
one_body_operator += FermionOperator(term, coefficient)
decomposed_operator += (test_eigenvalues[l] *
one_body_operator**2)
# Test for consistency.
difference = normal_ordered(decomposed_operator - fermion_operator)
errors += [difference.induced_norm()]
self.assertTrue(errors[-1] <= trunc_error)
self.assertTrue(errors[3] <= errors[2] <= errors[1] <= errors[0])
# Rank reduce by imposing final rank.
errors = []
for final_rank in [1, 2, 3, 4]:
# Decompose with threshold.
(test_eigenvalues, one_body_squares, one_body_correction,
trunc_error) = low_rank_two_body_decomposition(
two_body_coefficients, final_rank=final_rank)
# Make sure error is below truncation specification.
self.assertTrue(len(test_eigenvalues) == final_rank)
# Build back operator constant and one-body components.
decomposed_operator = FermionOperator((), constant)
one_body_coefficients = (molecule_interaction.one_body_tensor +
one_body_correction)
for p, q in itertools.product(range(n_qubits), repeat=2):
term = ((p, 1), (q, 0))
coefficient = one_body_coefficients[p, q]
decomposed_operator += FermionOperator(term, coefficient)
# Build back two-body component.
for l in range(final_rank):
one_body_operator = FermionOperator()
for p, q in itertools.product(range(n_qubits), repeat=2):
term = ((p, 1), (q, 0))
coefficient = one_body_squares[l, p, q]
one_body_operator += FermionOperator(term, coefficient)
decomposed_operator += (test_eigenvalues[l] *
one_body_operator**2)
# Test for consistency.
difference = normal_ordered(decomposed_operator - fermion_operator)
errors += [difference.induced_norm()]
self.assertTrue(errors[3] <= errors[2] <= errors[1] <= errors[0])
