I keep getting KeyError:0 message when I run the code

Question

I keep getting an error message like "KeyError:0" for this code when I ran it. The code is in two parts ("get_qubit_op(dist), and exact_solver(problem, converter)"). The first part does not give me any error but the second part gives me an error when I try to call the first part.

def get_qubit_op(dist):
    # Define Molecule
    molecule = Molecule(
        # Coordinates in Angstrom
        geometry=[
            ["Li", [0.0, 0.0, 0.0]],
            ["H", [dist, 0.0, 0.0]]
        ],
        multiplicity=1,  # = 2*spin + 1
        charge=0,
    )
driver = ElectronicStructureMoleculeDriver(
    molecule=molecule,
    basis="sto3g",
    driver_type=ElectronicStructureDriverType.PYSCF)

# Get properties
properties = driver.run()
num_particles = (properties
                    .get_property("ParticleNumber")
                    .num_particles)
num_spin_orbitals = int(properties
                        .get_property("ParticleNumber")
                        .num_spin_orbitals)

# Define Problem, Use freeze core approximation, remove orbitals.
problem = ElectronicStructureProblem(
    driver,
    [FreezeCoreTransformer(freeze_core=True,
                           remove_orbitals=[-3,-2])])

second_q_ops = problem.second_q_ops()  # Get 2nd Quant OP
num_spin_orbitals = problem.num_spin_orbitals
num_particles = problem.num_particles

mapper = ParityMapper()  # Set Mapper
hamiltonian = second_q_ops[0]  # Set Hamiltonian
# Do two qubit reduction
converter = QubitConverter(mapper,two_qubit_reduction=True)
reducer = TwoQubitReduction(num_particles)
qubit_op = converter.convert(hamiltonian)
qubit_op = reducer.convert(qubit_op)

return qubit_op, num_particles, num_spin_orbitals, problem, converter

def exact_solver(problem, converter):
    solver = NumPyMinimumEigensolverFactory()
    calc = GroundStateEigensolver(converter, solver)
    result = calc.solve(problem)
    return result

backend = BasicAer.get_backend("statevector_simulator")
distances = np.arange(0.5, 4.0, 0.2)
exact_energies = []
vqe_energies = []
optimizer = SLSQP(maxiter=5)

# pylint: disable=undefined-loop-variable
for dist in distances:
    (qubit_op, num_particles, num_spin_orbitals, problem, converter) = get_qubit_op(dist)
    result = exact_solver(problem,converter)
    exact_energies.append(result.total_energies[0].real)
    init_state = HartreeFock(num_spin_orbitals, num_particles, converter)
    var_form = UCCSD(converter,
                     num_particles,
                     num_spin_orbitals,
                     initial_state=init_state)
    vqe = VQE(var_form, optimizer, quantum_instance=backend)
    vqe_calc = vqe.compute_minimum_eigenvalue(qubit_op)
    vqe_result = problem.interpret(vqe_calc).total_energies[0].real
    vqe_energies.append(vqe_result)
    print(f"Interatomic Distance: {np.round(dist, 2)}",
          f"VQE Result: {vqe_result:.5f}",
          f"Exact Energy: {exact_energies[-1]:.5f}")

print("All energies have been calculated")

I was expecting it to work cuz its the same code in the textbook

I keep getting KeyError:0 message when I run the code

0 Answers0