# Copyright 2025 qBraid
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""
Module for conversions from QASM 3 to Cirq Circuits
"""
from __future__ import annotations
from typing import TYPE_CHECKING
import pyqasm
from qbraid_core._import import LazyLoader
from qbraid._logging import logger
from qbraid.passes.qasm.compat import normalize_if_blocks, replace_gate_names
from qbraid.programs.exceptions import QasmError
from qbraid.transpiler.annotations import weight
cirq_qasm_import = LazyLoader("cirq_contrib", globals(), "cirq.contrib.qasm_import")
if TYPE_CHECKING:
import cirq
from qbraid.programs.typer import Qasm3StringType
# Gate aliases that Cirq's built-in QASM parser does not recognize, mapped to
# their Cirq-supported equivalents.
_GATE_ALIASES = {
"cnot": "cx",
"si": "sdg",
"ti": "tdg",
"v": "sx",
"vi": "sxdg",
"phaseshift": "p",
"cphaseshift": "cp",
}
[docs]
@weight(1)
def qasm3_to_cirq(qasm: Qasm3StringType) -> cirq.Circuit:
"""Returns a Cirq circuit equivalent to the input OpenQASM 3 string.
Cirq's built-in importer handles most OpenQASM 2/3 directly, including
single-line conditionals. When it cannot, the program is normalized into a
form Cirq accepts -- gate aliases renamed, custom gates unrolled, barriers
removed, and QASM 3 braced ``if`` blocks rewritten to single-line syntax --
and parsing is retried.
Args:
qasm: OpenQASM 3 string to convert to a Cirq circuit.
Returns:
Cirq circuit representation equivalent to the input OpenQASM 3 string.
"""
try:
return cirq_qasm_import.circuit_from_qasm(qasm)
except cirq_qasm_import.QasmException:
pass
try:
qasm = replace_gate_names(qasm, _GATE_ALIASES)
qasm_module = pyqasm.loads(qasm)
qasm_module.unroll()
if qasm_module.has_barriers():
logger.warning(
"Barriers are not supported in Cirq, "
"and will be removed during program conversion."
)
qasm_module.remove_barriers()
qasm = normalize_if_blocks(pyqasm.dumps(qasm_module))
return cirq_qasm_import.circuit_from_qasm(qasm)
except cirq_qasm_import.QasmException as err:
raise QasmError(err) from err