# -*- coding: utf-8 -*-
# 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 dag to a circuit."""
from qiskit.circuit import QuantumCircuit
[docs]def dag_to_circuit(dag):
"""Build a ``QuantumCircuit`` object from a ``DAGCircuit``.
Args:
dag (DAGCircuit): the input dag.
Return:
QuantumCircuit: the circuit representing the input dag.
Example:
.. jupyter-execute::
from qiskit import QuantumRegister, ClassicalRegister, QuantumCircuit
from qiskit.dagcircuit import DAGCircuit
from qiskit.converters import circuit_to_dag
from qiskit.circuit.library.standard_gates import CHGate, U2Gate, CXGate
from qiskit.converters import dag_to_circuit
%matplotlib inline
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)
circuit = dag_to_circuit(dag)
circuit.draw()
"""
name = dag.name or None
circuit = QuantumCircuit(*dag.qregs.values(), *dag.cregs.values(), name=name)
for node in dag.topological_op_nodes():
# Get arguments for classical control (if any)
inst = node.op.copy()
inst.condition = node.condition
circuit._append(inst, node.qargs, node.cargs)
return circuit