def get_molecular_data(interaction_operator,
geometry=None,
basis=None,
multiplicity=None,
n_electrons=None,
reduce_spin=True,
data_directory=None):
"""Output a MolecularData object generated from an InteractionOperator
Args:
interaction_operator(InteractionOperator): two-body interaction
operator defining the "molecular interaction" to be simulated.
geometry(string or list of atoms):
basis(string): String denoting the basis set used to discretize the
system.
multiplicity(int): Spin multiplicity desired in the system.
n_electrons(int): Number of electrons in the system
reduce_spin(bool): True if one wishes to perform spin reduction on
integrals that are given in interaction operator. Assumes
spatial (x) spin structure generically.
Returns:
molecule(MolecularData):
Instance that captures the
interaction_operator converted into the format that would come
from an electronic structure package adorned with some meta-data
that may be useful.
"""
n_spin_orbitals = interaction_operator.n_qubits
# Introduce bare molecular operator to fill
molecule = MolecularData(geometry=geometry,
basis=basis,
multiplicity=multiplicity,
data_directory=data_directory)
molecule.nuclear_repulsion = interaction_operator.constant
# Remove spin from integrals and put into molecular operator
if reduce_spin:
reduction_indices = list(range(0, n_spin_orbitals, 2))
else:
reduction_indices = list(range(n_spin_orbitals))
molecule.n_orbitals = len(reduction_indices)
molecule.one_body_integrals = interaction_operator.one_body_tensor[
numpy.ix_(reduction_indices, reduction_indices)]
molecule.two_body_integrals = interaction_operator.two_body_tensor[
numpy.ix_(reduction_indices, reduction_indices, reduction_indices,
reduction_indices)]
# Fill in other metadata
molecule.overlap_integrals = numpy.eye(molecule.n_orbitals)
molecule.n_qubits = n_spin_orbitals
molecule.n_electrons = n_electrons
molecule.multiplicity = multiplicity
return molecule
def _build_of_molecule(self, molecule, mean_field):
"""Initialize the instance of Openfermion MolecularData class.
Interface the pyscf and Openfermion data.
`pyscf.ao2mo` is used to transform the AO integrals into
the MO integrals.
Args:
molecule (pyscf.gto.Mole): The molecule to simulate.
mean_field (pyscf.scf.RHF): The mean field of the molecule.
Returns:
openfermion.hamiltonian.MolecularData: Molecular Data in Openfermion (of_mole).
"""
of_mole = MolecularData(geometry=molecule.atom,
basis=molecule.basis,
multiplicity=molecule.spin + 1)
of_mole.mf = mean_field
of_mole.mol = molecule
of_mole.n_atoms = molecule.natm
of_mole.atoms = [row[0] for row in molecule.atom],
of_mole.protons = 0
of_mole.nuclear_repulsion = molecule.energy_nuc()
of_mole.charge = molecule.charge
of_mole.n_electrons = molecule.nelectron
of_mole.n_orbitals = len(mean_field.mo_energy)
of_mole.n_qubits = 2 * of_mole.n_orbitals
of_mole.hf_energy = mean_field.e_tot
of_mole.orbital_energies = mean_field.mo_energy
of_mole.mp2_energy = None
of_mole.cisd_energy = None
of_mole.fci_energy = None
of_mole.ccsd_energy = None
of_mole.general_calculations = {}
of_mole._canonical_orbitals = mean_field.mo_coeff
of_mole._overlap_integrals = mean_field.get_ovlp()
of_mole.h_core = mean_field.get_hcore()
of_mole._one_body_integrals = of_mole._canonical_orbitals.T @ of_mole.h_core @ of_mole._canonical_orbitals
twoint = mean_field._eri
eri = ao2mo.restore(8, twoint, of_mole.n_orbitals)
eri = ao2mo.incore.full(eri, of_mole._canonical_orbitals)
eri = ao2mo.restore(1, eri, of_mole.n_orbitals)
of_mole._two_body_integrals = np.asarray(eri.transpose(0, 2, 3, 1),
order='C')
return of_mole
def make_molecular_energy_obj(molecule_name,
basis="sto-3g",
geometry_info=None,
n_cancel_orbital=0,
n_frozen_orbital=0,
cas_irrep_nocc=None,
cas_irrep_ncore=None,
fermi_qubit_transform=bravyi_kitaev,
is_computed=False):
if geometry_info == None:
geometry_info = equilibrium_geometry_dict[molecule_name]
# Get geometry
if molecule_name not in geometry_generator_dict.keys():
print("No such example molecule, using default H2 hamiltonian.")
molecule_name = "H2"
geometry = geometry_generator_dict[molecule_name](geometry_info)
# Get fermion Hamiltonian
multiplicity = 1
charge = 0
molecule = MolecularData(geometry, basis, multiplicity, charge,
str(geometry_info))
molecule.symmetry = True
if not is_computed:
molecule = run_pyscf(molecule,
run_fci=1,
n_frozen_orbital=n_frozen_orbital,
n_cancel_orbital=n_cancel_orbital,
cas_irrep_nocc=cas_irrep_nocc,
cas_irrep_ncore=cas_irrep_ncore,
verbose=False)
molecule.load()
active_space_start = n_frozen_orbital
active_space_stop = molecule.n_orbitals - n_cancel_orbital
n_active_orb = active_space_stop - active_space_start
molecule.n_orbitals = n_active_orb
molecule.n_qubits = n_active_orb * 2
molecule.n_electrons = molecule.n_electrons - active_space_start * 2
fermion_hamiltonian = get_fermion_operator(
molecule.get_molecular_hamiltonian(
occupied_indices=molecule.frozen_orbitals,
active_indices=molecule.active_orbitals))
# Map ferimon Hamiltonian to qubit Hamiltonian
qubit_hamiltonian = fermi_qubit_transform(fermion_hamiltonian)
# qubit_electron_operator=fermi_qubit_transform(get_electron_fermion_operator(molecule.n_electrons))
qubit_electron_operator = get_HF_operator(molecule.n_electrons,
fermi_qubit_transform)
# qubit_hamiltonian=get_dressed_operator(qubit_electron_operator,qubit_hamiltonian)
# Ignore terms in Hamiltonian that close to zero
qubit_hamiltonian.compress()
# Set the terminate_energy to be achieving the chemical accuracy
terminate_energy = molecule.fci_energy + CHEMICAL_ACCURACY
obj_info = {
"n_qubit": molecule.n_qubits,
"start_cost": molecule.hf_energy,
"terminate_cost": terminate_energy
}
init_operator = HartreeFockInitBlock(
get_operator_qsubset(qubit_electron_operator))
return EnergyObjective(qubit_hamiltonian, molecule.n_qubits, init_operator,
obj_info)