# Copyright (C) 2020 Unitary Fund
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <https://www.gnu.org/licenses/>.
"""Functions for generating randomized benchmarking circuits."""
from typing import List, Optional, cast
import numpy as np
from cirq.experiments.qubit_characterizations import (
_single_qubit_cliffords,
_random_single_q_clifford,
_random_two_q_clifford,
_gate_seq_to_mats,
_two_qubit_clifford_matrices,
)
from cirq import LineQubit
from mitiq import QPROGRAM
from mitiq.interface import convert_from_mitiq
[docs]def generate_rb_circuits(
n_qubits: int,
num_cliffords: int,
trials: int = 1,
return_type: Optional[str] = None,
) -> List[QPROGRAM]:
"""Returns a list of randomized benchmarking circuits, i.e. circuits that
are equivalent to the identity.
Args:
n_qubits: The number of qubits. Can be either 1 or 2.
num_cliffords: The number of Clifford group elements in the
random circuits. This is proportional to the depth per circuit.
trials: The number of random circuits at each num_cfd.
return_type: String which specifies the type of the
returned circuits. See the keys of
``mitiq.SUPPORTED_PROGRAM_TYPES`` for options. If ``None``, the
returned circuits have type ``cirq.Circuit``.
Returns:
A list of randomized benchmarking circuits.
"""
if n_qubits not in (1, 2):
raise ValueError(
"Only generates RB circuits on one or two "
f"qubits not {n_qubits}."
)
qubits = LineQubit.range(n_qubits)
cliffords = _single_qubit_cliffords()
if n_qubits == 1:
c1 = cliffords.c1_in_xy
cfd_mat_1q = cast(
np.ndarray, [_gate_seq_to_mats(gates) for gates in c1]
)
circuits = [
_random_single_q_clifford(qubits[0], num_cliffords, c1, cfd_mat_1q)
for _ in range(trials)
]
else:
cfd_matrices = _two_qubit_clifford_matrices(
qubits[0], qubits[1], cliffords,
)
circuits = [
_random_two_q_clifford(
qubits[0], qubits[1], num_cliffords, cfd_matrices, cliffords,
)
for _ in range(trials)
]
return_type = "cirq" if not return_type else return_type
return [convert_from_mitiq(circuit, return_type) for circuit in circuits]