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circuit_to_dag.py
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circuit_to_dag.py
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# This code is part of Qiskit.
#
# (C) Copyright IBM 2017, 2018.
#
# This code is licensed under the Apache License, Version 2.0. You may
# obtain a copy of this license in the LICENSE.txt file in the root directory
# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
#
# Any modifications or derivative works of this code must retain this
# copyright notice, and modified files need to carry a notice indicating
# that they have been altered from the originals.
"""Helper function for converting a circuit to a dag"""
import copy
from qiskit.dagcircuit.dagcircuit import DAGCircuit
def circuit_to_dag(circuit, copy_operations=True, *, qubit_order=None, clbit_order=None):
"""Build a :class:`.DAGCircuit` object from a :class:`.QuantumCircuit`.
Args:
circuit (QuantumCircuit): the input circuit.
copy_operations (bool): Deep copy the operation objects
in the :class:`~.QuantumCircuit` for the output :class:`~.DAGCircuit`.
This should only be set to ``False`` if the input :class:`~.QuantumCircuit`
will not be used anymore as the operations in the output
:class:`~.DAGCircuit` will be shared instances and modifications to
operations in the :class:`~.DAGCircuit` will be reflected in the
:class:`~.QuantumCircuit` (and vice versa).
qubit_order (Iterable[~qiskit.circuit.Qubit] or None): the order that the qubits should be
indexed in the output DAG. Defaults to the same order as in the circuit.
clbit_order (Iterable[Clbit] or None): the order that the clbits should be indexed in the
output DAG. Defaults to the same order as in the circuit.
Return:
DAGCircuit: the DAG representing the input circuit.
Raises:
ValueError: if the ``qubit_order`` or ``clbit_order`` parameters do not match the bits in
the circuit.
Example:
.. code-block::
from qiskit import QuantumRegister, ClassicalRegister, QuantumCircuit
from qiskit.dagcircuit import DAGCircuit
from qiskit.converters import circuit_to_dag
q = QuantumRegister(3, 'q')
c = ClassicalRegister(3, 'c')
circ = QuantumCircuit(q, c)
circ.h(q[0])
circ.cx(q[0], q[1])
circ.measure(q[0], c[0])
circ.rz(0.5, q[1]).c_if(c, 2)
dag = circuit_to_dag(circ)
"""
dagcircuit = DAGCircuit()
dagcircuit.name = circuit.name
dagcircuit.global_phase = circuit.global_phase
dagcircuit.calibrations = circuit.calibrations
dagcircuit.metadata = circuit.metadata
if qubit_order is None:
qubits = circuit.qubits
elif len(qubit_order) != circuit.num_qubits or set(qubit_order) != set(circuit.qubits):
raise ValueError("'qubit_order' does not contain exactly the same qubits as the circuit")
else:
qubits = qubit_order
if clbit_order is None:
clbits = circuit.clbits
elif len(clbit_order) != circuit.num_clbits or set(clbit_order) != set(circuit.clbits):
raise ValueError("'clbit_order' does not contain exactly the same clbits as the circuit")
else:
clbits = clbit_order
dagcircuit.add_qubits(qubits)
dagcircuit.add_clbits(clbits)
for register in circuit.qregs:
dagcircuit.add_qreg(register)
for register in circuit.cregs:
dagcircuit.add_creg(register)
for instruction in circuit.data:
op = instruction.operation
if copy_operations:
op = copy.deepcopy(op)
dagcircuit.apply_operation_back(op, instruction.qubits, instruction.clbits, check=False)
dagcircuit.duration = circuit.duration
dagcircuit.unit = circuit.unit
return dagcircuit