Bug: Max Qubit number limit Hamiltonian Simulation

[PetarJurcevic]

Running the current Hamiltonian Simulation with >20Q gives:

---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
Cell In[15], line 4
      2 sys.path.insert(1, "hamiltonian-simulation/qiskit")
      3 import hamiltonian_simulation_benchmark
----> 4 hamiltonian_simulation_benchmark.run(min_qubits=min_qubits, max_qubits=max_qubits, skip_qubits=skip_qubits,
      5                 max_circuits=max_circuits, num_shots=num_shots,
      6                 backend_id=backend_id, provider_backend=provider_backend,
      7                 hub=hub, group=group, project=project, exec_options=exec_options)

File c:\Users\2J7579897\Notebooks_general\QEDC-benchmark\QC-App-Oriented-Benchmarks\hamiltonian-simulation/qiskit\hamiltonian_simulation_benchmark.py:286, in run(min_qubits, max_qubits, max_circuits, skip_qubits, num_shots, use_XX_YY_ZZ_gates, backend_id, provider_backend, hub, group, project, exec_options, context)
    284 h_x = precalculated_data['h_x'][:num_qubits] # precalculated random numbers between [-1, 1]
    285 h_z = precalculated_data['h_z'][:num_qubits]
--> 286 qc = HamiltonianSimulation(num_qubits, K=k, t=t, w=w, h_x= h_x, h_z=h_z)
    287 metrics.store_metric(num_qubits, circuit_id, 'create_time', time.time() - ts)
    289 # collapse the sub-circuits used in this benchmark (for qiskit)

File c:\Users\2J7579897\Notebooks_general\QEDC-benchmark\QC-App-Oriented-Benchmarks\hamiltonian-simulation/qiskit\hamiltonian_simulation_benchmark.py:70, in HamiltonianSimulation(n_spins, K, t, w, h_x, h_z)
     66 # loop over each trotter step, adding gates to the circuit defining the hamiltonian
     67 for k in range(K):
     68 
     69     # the Pauli spin vector product
---> 70     [qc.rx(2 * tau * w * h_x[i], qr[i]) for i in range(n_spins)]
     71     [qc.rz(2 * tau * w * h_z[i], qr[i]) for i in range(n_spins)]
     72     qc.barrier()
...
---> 70     [qc.rx(2 * tau * w * h_x[i], qr[i]) for i in range(n_spins)]
     71     [qc.rz(2 * tau * w * h_z[i], qr[i]) for i in range(n_spins)]
     72     qc.barrier()

Possible Fix: in precalculated_data.ipynb increase hardcoded limits:

• line 19: precalculated_data['h_x'] = list(2 * np.random.random(39) - 1)
• line 21: precalculated_data['h_z'] = list(2 * np.random.random(29) - 1)
• line 25: for n_spins in range(2,40)

or make the limits dynamic based on max_qubit_number, however, this will require a recalculation with every initialization

[rtvuser1]

We only do initialization at the beginning of a run of the whole benchmark, so I don't think dynamically initializing will be a problem. How large do you need the num_qubits to go?