Source code for qlauncher.problems.problem_initialization.molecule

 1from qiskit.quantum_info import SparsePauliOp
 2
 3from qiskit_nature.second_q.formats.molecule_info import MoleculeInfo
 4from qiskit_nature.second_q.drivers import PySCFDriver
 5from qiskit_nature.second_q.mappers import ParityMapper, QubitMapper
 6from qiskit_nature.second_q.problems import ElectronicStructureProblem
 7
 8from qlauncher.base import Problem
 9
10

[docs]
11class Molecule(Problem):
12    def __init__(self, instance: MoleculeInfo, mapper: QubitMapper | None = None, basis_set: str = 'STO-6G', instance_name: str = 'unnamed') -> None:
13        self.basis_set = basis_set
14        self.mapper = ParityMapper() if mapper is None else mapper
15        self.problem: ElectronicStructureProblem = self._get_problem(instance)
16        self.operator: SparsePauliOp = self._get_operator(self.problem)
17        super().__init__(instance, instance_name)
18

[docs]
19    @staticmethod
20    def from_preset(instance_name: str) -> "Molecule":
21        match instance_name:
22            case 'H2':
23                instance = MoleculeInfo(["H", "H"], [(0.0, 0.0, 0.0), (0.0, 0.0, 0.74)])
24            case _:
25                raise ValueError(f"Molecule {instance_name} not supported, currently you can use: 'H2'")
26        return Molecule(instance, instance_name=instance_name)

27
28    def _get_problem(self, molecule) -> ElectronicStructureProblem:
29        driver = PySCFDriver.from_molecule(molecule, basis=self.basis_set)
30        problem = driver.run()
31        return problem
32
33    def _get_operator(self, problem) -> SparsePauliOp:
34        self.mapper.num_particles = problem.num_particles
35        hamiltonian = self.mapper.map(problem.hamiltonian.second_q_op())
36        if not isinstance(hamiltonian, SparsePauliOp):
37            raise ValueError
38        return hamiltonian