I am trying to calculate the ground state energy of some simple molecules using 'MolecularGroundStateEnergy' tools in qiskit. When I run the calculations for very small molecules (e.g. H2, HeH+) the jobs appear in the queue very quickly and the calculations work independent of which backend I select. However, running the same code with slightly larger molecules (e.g. LiH, BeH2 and water) the jupyter notebook runs indefinitely and the jobs do not show in the IMBQ queue.
Note: I have run successful calculations for all these molecules using the state-vector simulator with no issues.
Here is the function i use to calculate energy via VQE given a molecule (created from PySCF driver):
def calc_vqe_energy(molecule): driver = molecule energy = MolecularGroundStateEnergy(driver = driver, transformation=TransformationType('full'), qubit_mapping=QubitMappingType('parity'), two_qubit_reduction=True, freeze_core=False, z2symmetry_reduction='auto') solver = energy.get_default_solver(quantum_instance) #calculate energy using the above solver calc = energy.compute_energy(solver) return calc
this is set up to run using the quantum instance:
IBMQ.save_account(token) IBMQ.load_account() provider = IBMQ.get_provider(hub='ibm-q') backend = provider.get_backend("ibmq_qasm_simulator") coupling_map = backend.configuration().coupling_map quantum_instance = QuantumInstance(backend=backend, shots=1000, coupling_map=coupling_map, measurement_error_mitigation_cls=CompleteMeasFitter, cals_matrix_refresh_period=30, skip_qobj_validation=False)
Thanks for the help!