# Copyright 2021 Huawei Technologies Co., Ltd
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# ============================================================================
"""UCCSD ansatz."""
import itertools
from collections import OrderedDict
import numpy as np
from mindquantum.core.circuit import Circuit, decompose_single_term_time_evolution
from mindquantum.core.operators import FermionOperator, down_index, up_index
from mindquantum.third_party.interaction_operator import InteractionOperator
from mindquantum.utils.type_value_check import _require_package
from .transform import Transform
def _para_uccsd_singlet_generator(mol, threshold=0): # pylint: disable=too-many-locals,too-many-statements
"""
Generate a uccsd quantum circuit.
Args:
mol (molecular): A hdf5 molecular file generated by HiQ Fermion.
threshold (float, optional): A threshold of parameters. If the absolute value of parameter is
lower than the threshold, than we will not update it in VQE
algorithm. Default: ``0``.
"""
n_qubits = mol.n_qubits
n_electrons = mol.n_electrons
params = {}
if n_qubits % 2 != 0:
raise ValueError('The total number of spin-orbitals should be even.')
out = []
out_tmp = []
n_spatial_orbitals = n_qubits // 2
n_occupied = int(np.ceil(n_electrons / 2))
n_virtual = n_spatial_orbitals - n_occupied
# Unpack amplitudes
n_single_amplitudes = n_occupied * n_virtual
# Generate excitations
spin_index_functions = [up_index, down_index]
# Generate all spin-conserving single and double excitations derived
# from one spatial occupied-virtual pair
for i, (p, q) in enumerate(itertools.product(range(n_virtual), range(n_occupied))): # pylint: disable=invalid-name
# Get indices of spatial orbitals
virtual_spatial = n_occupied + p
occupied_spatial = q
virtual_up = virtual_spatial * 2
occupied_up = occupied_spatial * 2
virtual_down = virtual_spatial * 2 + 1
occupied_down = occupied_spatial * 2 + 1
single_amps = mol.ccsd_single_amps[virtual_up, occupied_up]
double1_amps = mol.ccsd_double_amps[virtual_up, occupied_up, virtual_down, occupied_down]
single_amps_name = 'p' + str(i)
double1_amps_name = 'p' + str(i + n_single_amplitudes)
for spin in range(2):
# Get the functions which map a spatial orbital index to a
# spin orbital index
this_index = spin_index_functions[spin]
other_index = spin_index_functions[1 - spin]
# Get indices of spin orbitals
virtual_this = this_index(virtual_spatial)
virtual_other = other_index(virtual_spatial)
occupied_this = this_index(occupied_spatial)
occupied_other = other_index(occupied_spatial)
# Generate single excitations
if abs(single_amps) > threshold:
params[single_amps_name] = single_amps
fermion_ops1 = FermionOperator(((occupied_this, 1), (virtual_this, 0)), 1)
fermion_ops2 = FermionOperator(((virtual_this, 1), (occupied_this, 0)), 1)
out.append([fermion_ops1 - fermion_ops2, single_amps_name])
# Generate double excitation
if abs(double1_amps) > threshold:
params[double1_amps_name] = double1_amps
fermion_ops1 = FermionOperator(
((virtual_this, 1), (occupied_this, 0), (virtual_other, 1), (occupied_other, 0)), 1
)
fermion_ops2 = FermionOperator(
((occupied_other, 1), (virtual_other, 0), (occupied_this, 1), (virtual_this, 0)), 1
)
out.append([fermion_ops1 - fermion_ops2, double1_amps_name])
out.extend(out_tmp)
out_tmp = []
# Generate all spin-conserving double excitations derived
# from two spatial occupied-virtual pairs
for i, ((p, q), (r, s)) in enumerate( # pylint: disable=invalid-name
itertools.combinations(itertools.product(range(n_virtual), range(n_occupied)), 2)
):
# Get indices of spatial orbitals
virtual_spatial_1 = n_occupied + p
occupied_spatial_1 = q
virtual_spatial_2 = n_occupied + r
occupied_spatial_2 = s
virtual_1_up = virtual_spatial_1 * 2
occupied_1_up = occupied_spatial_1 * 2
virtual_2_up = virtual_spatial_2 * 2 + 1
occupied_2_up = occupied_spatial_2 * 2 + 1
double2_amps = mol.ccsd_double_amps[virtual_1_up, occupied_1_up, virtual_2_up, occupied_2_up]
double2_amps_name = 'p' + str(i + 2 * n_single_amplitudes)
# Generate double excitations
for (spin_a, spin_b) in itertools.product(range(2), repeat=2):
# Get the functions which map a spatial orbital index to a
# spin orbital index
index_a = spin_index_functions[spin_a]
index_b = spin_index_functions[spin_b]
# Get indices of spin orbitals
virtual_1_a = index_a(virtual_spatial_1)
occupied_1_a = index_a(occupied_spatial_1)
virtual_2_b = index_b(virtual_spatial_2)
occupied_2_b = index_b(occupied_spatial_2)
if abs(double2_amps) > threshold:
params[double2_amps_name] = double2_amps
fermion_ops1 = FermionOperator(
((virtual_1_a, 1), (occupied_1_a, 0), (virtual_2_b, 1), (occupied_2_b, 0)), 1
)
fermion_ops2 = FermionOperator(
((occupied_2_b, 1), (virtual_2_b, 0), (occupied_1_a, 1), (virtual_1_a, 0)), 1
)
out.append([fermion_ops1 - fermion_ops2, double2_amps_name])
return out, params
def _transform2pauli(fermion_ansatz):
"""Transform a fermion ansatz to pauli ansatz based on jordan-wigner transformation."""
out = OrderedDict()
for i in fermion_ansatz:
qubit_generator = Transform(i[0]).jordan_wigner()
if qubit_generator.terms:
for key, term in qubit_generator.terms.items():
if key not in out:
out[key] = OrderedDict({i[1]: float(term.imag)})
else:
if i[1] in out[key]:
out[key][i[1]] += float(term.imag)
else:
out[key][i[1]] = float(term.imag)
return out
def _pauli2circuit(pauli_ansatz):
"""Transform a pauli ansatz to parameterized quantum circuit."""
circuit = Circuit()
for k, v in pauli_ansatz.items():
circuit += decompose_single_term_time_evolution(k, v)
return circuit
[文档]def generate_uccsd(molecular, threshold=0):
"""
Generate a uccsd quantum circuit based on a molecular data generated by Openfermion.
Args:
molecular (Union[str, MolecularData]): the name of the molecular data file,
or openfermion MolecularData.
threshold (float): the threshold to filter out the uccsd amplitude. We only keep the
excitation operator with absolute value of amplitude greater than `threshold`, so
that if `threshold=0`, we only keep excitation operator with non zero amplitude. Default: ``0``.
Returns:
- **uccsd_circuit** (Circuit), the ansatz circuit generated by uccsd method.
- **initial_amplitudes** (numpy.ndarray), the initial parameter values of uccsd circuit.
- **parameters_name** (list[str]), the name of initial parameters.
- **qubit_hamiltonian** (QubitOperator), the hamiltonian of the molecule.
- **n_qubits** (int), the number of qubits in simulation.
- **n_electrons** (int), the number of electrons of the molecule.
"""
try:
# pylint: disable=import-outside-toplevel
from openfermion.chem import MolecularData
except (ImportError, AttributeError):
_require_package("openfermion", "1.5.0")
if isinstance(molecular, str):
mol = MolecularData(filename=molecular)
mol.load()
else:
mol = molecular
print(f"ccsd:{mol.ccsd_energy}.")
print(f"fci:{mol.fci_energy}.")
fermion_ansatz, parameters = _para_uccsd_singlet_generator(mol, threshold)
pauli_ansatz = _transform2pauli(fermion_ansatz)
uccsd_circuit = _pauli2circuit(pauli_ansatz)
ham_of = mol.get_molecular_hamiltonian()
inter_ops = InteractionOperator(*ham_of.n_body_tensors.values())
ham_hiq = FermionOperator(inter_ops)
qubit_hamiltonian = Transform(ham_hiq).jordan_wigner()
qubit_hamiltonian = qubit_hamiltonian.compress()
parameters_name = list(parameters.keys())
initial_amplitudes = [parameters[i] for i in parameters_name]
return uccsd_circuit, initial_amplitudes, parameters_name, qubit_hamiltonian, mol.n_qubits, mol.n_electrons