def __init__(self,
hamiltonian: openfermion.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, _ = (
openfermion.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 = (
openfermion.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 = openfermion.QuadraticHamiltonian(one_body_coefficients)
self.one_body_energies, self.one_body_basis_change_matrix, _ = (
quad_ham.diagonalizing_bogoliubov_transform()
)
super().__init__(hamiltonian)
def __init__(self,
hamiltonian: openfermion.InteractionOperator,
iterations: int=1,
final_rank: Optional[int]=None,
include_all_cz: bool=False,
include_all_z: bool=False,
adiabatic_evolution_time: Optional[float]=None,
spin_basis: bool=True,
qubits: Optional[Sequence[cirq.Qid]]=None
) -> None:
"""
Args:
hamiltonian: The Hamiltonian used to generate the ansatz
circuit and default initial parameters.
iterations: The number of iterations of the basic template to
include in the circuit. The number of parameters grows linearly
with this value.
final_rank: The rank at which to truncate the decomposition.
include_all_cz: Whether to include all possible CZ-type
parameterized gates in the ansatz (irrespective of the ansatz
Hamiltonian)
include_all_z: Whether to include all possible Z-type
parameterized gates in the ansatz (irrespective of the ansatz
Hamiltonian)
adiabatic_evolution_time: The time scale for Hamiltonian evolution
used to determine the default initial parameters of the ansatz.
This is the value A from the docstring of this class.
If not specified, defaults to the sum of the absolute values
of the entries of the two-body tensor of the Hamiltonian.
spin_basis: Whether the Hamiltonian is given in the spin orbital
(rather than spatial orbital) basis.
qubits: Qubits to be used by the ansatz circuit. If not specified,
then qubits will automatically be generated by the
`_generate_qubits` method.
"""
self.hamiltonian = hamiltonian
self.iterations = iterations
self.final_rank = final_rank
self.include_all_cz = include_all_cz
self.include_all_z = include_all_z
if adiabatic_evolution_time is None:
adiabatic_evolution_time = (
numpy.sum(numpy.abs(hamiltonian.two_body_tensor)))
self.adiabatic_evolution_time = cast(float, adiabatic_evolution_time)
# Perform the low rank decomposition of two-body operator.
self.eigenvalues, one_body_squares, self.one_body_correction, _ = (
openfermion.low_rank_two_body_decomposition(
hamiltonian.two_body_tensor,
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 = (
openfermion.prepare_one_body_squared_evolution(
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 + self.one_body_correction)
quad_ham = openfermion.QuadraticHamiltonian(one_body_coefficients)
self.one_body_energies, self.one_body_basis_change_matrix, _ = (
quad_ham.diagonalizing_bogoliubov_transform()
)
super().__init__(qubits)
