Pauli Twirling with FiQCI EMS

Pauli Twirling with FiQCI EMS#

What is Pauli Twirling#

Pauli Twirling is an error mitigation (or tailoring) technique that aims to transform gate noise towards a stochastic Pauli channel which can be more efficiently mitigated by other methods. Pauli twirling generates multiple variants of a circuit by sandwiching gates in between random sets of Pauli gates. These random Pauli sets are chosen so that the action of the sandwiched gate is equal to just the original gate. The results of all the variant circuits can then be averaged to get the mitigated/tailored results.

The steps are then:

  1. Generate variant circuits by sandwiching two-qubit gates between Pauli channels that cancel out.

  2. Execute all variant circuits

  3. Average the results from execution

Usage#

Using the FiQCISampler or FiQCIBackend Pauli Twirling can be enabled by setting mitigation_level=3. With FiQCIEstimator it needs to be manually configured with pauli_twirl().

from fiqci.ems import FiQCISampler

sampler = FiQCIEstimator(backend=backend, mitigation_level=3)

Manual Configuration#

For fine-grained control, enable Pauli Twirling explicitly via the pauli_twirl() method of the primitive:

from qiskit.circuit.library import CZGate

estimator = FiQCIEstimator(backend=backend, mitigation_level=1)

estimator.pauli_twirl(
    enabled=True,
    num_twirls=5,
    gates_to_twirl=[CZGate()]
)

References#