KeyError: 0 problem. Is there a way to fix?-CodePudding

I'm quite new to quantum coding and i keep on getting this error in my code.


***hamiltonian = second_q_ops[0]***
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) 
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) 
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, `your text`
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") 
plt.plot(distances, exact_energies, label="Exact Energy") 
plt.plot(distances, vqe_energies, label="VQE Energy") 
plt.xlabel('Atomic distance (Angstrom)') 
plt.ylabel('Energy') 
plt.legend() 
plt.show()

The problem is in bold.it says:
Traceback (most recent call last):
  Input In [8] in <cell line: 132>
    problem, converter) = get_qubit_op(dist)
  Input In [8] in get_qubit_op
    hamiltonian = second_q_ops[0]
KeyError: 0

Can anyone help me? Thanks Full script in this link. Quantum code

I tried Changing the variabes in those two parts of the error to 0 but it gave me KeyError: Ill Geometry. I also tried changing the number to different things but it didn't work.

CodePudding user response：

That error is due to a interface change in qiskit_nature, where aux_operators are now returned as dictionaries instead of lists.

You can temporarily switch back to the old behavior by adding the following two lines to the top of your script:

from qiskit_nature.settings import settings
settings.dict_aux_operators = False

in the long run, you should migrate your code to the updated interface.