# -*- coding: utf-8 -*-
# This code is part of Qiskit.
#
# (C) Copyright IBM 2019.
#
# 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.
"""Transform a circuit with virtual qubits into a circuit with physical qubits."""
from qiskit.circuit import QuantumRegister
from qiskit.dagcircuit import DAGCircuit
from qiskit.transpiler.basepasses import TransformationPass
from qiskit.transpiler.exceptions import TranspilerError
[docs]class ApplyLayout(TransformationPass):
"""Transform a circuit with virtual qubits into a circuit with physical qubits.
Transforms a DAGCircuit with virtual qubits into a DAGCircuit with physical qubits
by applying the Layout given in `property_set`.
Requires either of passes to set/select Layout, e.g. `SetLayout`, `TrivialLayout`.
Assumes the Layout has full physical qubits.
"""
[docs] def run(self, dag):
"""Run the ApplyLayout pass on `dag`.
Args:
dag (DAGCircuit): DAG to map.
Returns:
DAGCircuit: A mapped DAG (with physical qubits).
Raises:
TranspilerError: if no layout is found in `property_set` or no full physical qubits.
"""
layout = self.property_set["layout"]
if not layout:
raise TranspilerError(
"No 'layout' is found in property_set. Please run a Layout pass in advance.")
if len(layout) != (1 + max(layout.get_physical_bits())):
raise TranspilerError(
"The 'layout' must be full (with ancilla).")
q = QuantumRegister(len(layout), 'q')
new_dag = DAGCircuit()
new_dag.add_qreg(q)
for creg in dag.cregs.values():
new_dag.add_creg(creg)
for node in dag.topological_op_nodes():
if node.type == 'op':
qargs = [q[layout[qarg]] for qarg in node.qargs]
new_dag.apply_operation_back(node.op, qargs, node.cargs, node.condition)
return new_dag