# 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 converting Braket circuits to/from OpenQASM 3
"""
from __future__ import annotations
from typing import TYPE_CHECKING
import pyqasm
from openqasm3 import ast
from openqasm3.visitor import QASMVisitor
from pyqasm.exceptions import ValidationError
from qbraid_core._import import LazyLoader
from qbraid.passes.qasm.compat import (
remove_stdgates_include,
replace_gate_names,
)
from qbraid.programs.exceptions import QasmError
from qbraid.transpiler.annotations import weight
braket_circuits = LazyLoader("braket_circuits", globals(), "braket.circuits")
braket_openqasm = LazyLoader("braket_openqasm", globals(), "braket.ir.openqasm")
if TYPE_CHECKING:
import braket.circuits
from qbraid.programs.typer import Qasm3StringType
class _DelayFinder(QASMVisitor):
"""Records whether a program contains a ``delay`` instruction."""
def __init__(self):
self.found = False
# pylint: disable-next=invalid-name,unused-argument
def visit_DelayInstruction(self, node: ast.DelayInstruction, context=None) -> None:
"""Record that the program contains a delay instruction."""
self.found = True
def contains_delay(program: ast.Program) -> bool:
"""Check whether a parsed OpenQASM 3 program contains a ``delay`` instruction.
Traverses the AST directly so nested delays (e.g. inside a ``box``) are caught too.
Args:
program: A parsed OpenQASM 3 AST (e.g. ``pyqasm.loads(qasm).original_program``).
Returns:
True if the program contains a delay instruction, False otherwise.
"""
finder = _DelayFinder()
finder.visit(program)
return finder.found
def transform_notation(qasm3: str) -> str:
"""
Process an OpenQASM 3 program that was generated by
an external tool to make it compatible with Amazon Braket.
"""
replacements = {
"cx": "cnot",
"ccx": "ccnot",
"sdg": "si",
"tdg": "ti",
"sx": "v",
"id": "i",
"sxdg": "vi",
"p": "phaseshift",
"cp": "cphaseshift",
}
qasm3 = remove_stdgates_include(qasm3)
qasm3 = replace_gate_names(qasm3, replacements)
return qasm3
[docs]
@weight(1)
def qasm3_to_braket(qasm: Qasm3StringType) -> braket.circuits.Circuit:
"""Converts an OpenQASM 3.0 string to a ``braket.circuits.Circuit``.
Args:
qasm: OpenQASM 3 string
Returns:
The Amazon Braket circuit equivalent to the input OpenQASM 3.0 string
Raises:
QasmError: If qasm to braket conversion fails, or if the program contains
a delay instruction, which Braket cannot represent.
"""
prior_errors: list[tuple[str, BaseException]] = []
try:
module = pyqasm.loads(qasm)
except ValidationError as err:
module = None
prior_errors.append(("PyQASM validation", err))
# Braket has no gate-level delay and silently drops delay instructions inside
# Circuit.from_ir, producing a circuit that runs but measures the wrong thing. Detect
# delays up front and fail loudly. ``original_program`` is populated by ``loads`` even
# when a later ``unroll`` would reject the program (e.g. a verbatim box), so this reuses
# the parse pyqasm already did without a second one and still catches nested delays.
if module is not None and contains_delay(module.original_program):
raise QasmError("Delay instructions are not supported by Amazon Braket.")
if module is not None:
try:
module.unroll()
qasm = pyqasm.dumps(module)
except ValidationError as err:
prior_errors.append(("PyQASM validation", err))
try:
qasm = transform_notation(qasm)
except Exception as err: # pylint: disable=broad-exception-caught
prior_errors.append(("Transform", err))
try:
program = braket_openqasm.Program(source=qasm)
return braket_circuits.Circuit.from_ir(source=program.source, inputs=program.inputs)
except Exception as err:
msg = f"Error converting qasm3 string to braket circuit: {err}"
if prior_errors:
msg += ". Prior errors: " + "; ".join(f"{label}: {e}" for label, e in prior_errors)
raise QasmError(msg) from err