demo_spin.py

import os
from qiskit_nature_qe import qe_driver
from qiskit_algorithms import NumPyMinimumEigensolver
from qiskit_nature.second_q.mappers import JordanWignerMapper
from qiskit_nature.second_q.algorithms import GroundStateEigensolver
from qiskit.exceptions import QiskitError

if __name__ == "__main__":
    hdf5_up_file = os.path.join(
        "qe_files", "out_H2_spin", "H2_spin.save", "wfcup1.hdf5"
    )
    hdf5_dw_file = os.path.join(
        "qe_files", "out_H2_spin", "H2_spin.save", "wfcdw1.hdf5"
    )
    xml_file = os.path.join(
        "qe_files", "out_H2_spin", "H2_spin.save", "data-file-schema.xml"
    )

    driver = qe_driver.QE_Driver([hdf5_up_file, hdf5_dw_file], xml_file)

    problem = driver.run()

    # ------------------ Solve with NumPyMinimumEigensolver ------------------
    mapper = JordanWignerMapper()
    algo = NumPyMinimumEigensolver()
    algo.filter_criterion = problem.get_default_filter_criterion()

    solver = GroundStateEigensolver(mapper, algo)
    # FIXME: Get numpy ground state solver running
    try:
        result = solver.solve(problem)
        print(result)
    except QiskitError as e:
        print("Could not find ground-state!")