r"""Running  SPAM error mitigation via Qermit MitRes on measurement of expectation value for H2."""


from inquanto.protocols import gen_UnCorrelated_SPAM_MitRes

from inquanto.ansatzes import MultiConfigurationStateSparse
from inquanto.express import get_noisy_backend, load_h5
from inquanto.protocols import PauliAveraging

# get an example system from express database, get fermionic objects, and qubit encode
h2 = load_h5("h2_sto3g_symmetry.h5", as_tuple=True)
print("HF energy:", h2.energy_hf)
hamiltonian = h2.hamiltonian_operator
state = h2.hf_state
qstate = state.qubit_encode()
kernel = hamiltonian.qubit_encode()

# prepare a compact chemical ansatz, just Hartree-Fock here as an example (note it has no symbols)
ansatz = MultiConfigurationStateSparse(qstate)

noisy_backend = get_noisy_backend(ansatz.n_qubits)

# SPAM error mitigation.
spam = gen_UnCorrelated_SPAM_MitRes(
    backend=noisy_backend,
    calibration_shots=1000,
    num_calibration_qubits=ansatz.n_qubits,
)

# instantiate and build the protocol.
protocol = PauliAveraging(
    noisy_backend,
    shots_per_circuit=1000,
)
protocol.build(
    {},
    ansatz,
    kernel,
    noise_mitigation=None,
).compile_circuits()

# run the protocol via SPAM MitRes
protocol.run_mitres(spam)

exp_val = protocol.evaluate_expectation_value(ansatz, kernel)
print("Energy from SPAM-mitigated measurement:", exp_val)