ApplyLayout
class qiskit.transpiler.passes.ApplyLayout(*args, **kwargs)
Bases: TransformationPass
Apply or update the mapping of virtual qubits to physical qubits in the DAGCircuit.
A “layout” in Qiskit is a mapping of virtual qubits (as the user typically creates circuits in terms of) to the physical qubits used to represent them on hardware.
This pass has two modes of operation, depending on the state of the layout and post_layout keys in the PropertySet:
-
Standard operation:
post_layoutis not set. This takes in aDAGCircuitdefined over virtual qubits, and rewrites it in terms of physical qubits. In this case, thelayoutfield must have been chosen by a layout pass (for exampleSetLayoutorVF2Layout), and both it and theDAGCircuitmust have been expanded with ancillas (seeEnlargeWithAncillaandFullAncillaAllocation). -
Improving a layout:
post_layoutis set (such as byVF2PostLayout). In this case, thepost_layoutmust already be the correct size. It is interpreted as an _additional_ relabelling on top of the relabelling that is already applied to the inputDAGCircuit.After the pass runs, the
layoutfield will be updated to represent the composition of the two relabellings, as will theDAGCircuitand any final permutation. Thepost_layoutfield will be removed.
Attributes
is_analysis_pass
Check if the pass is an analysis pass.
If the pass is an AnalysisPass, that means that the pass can analyze the DAG and write the results of that analysis in the property set. Modifications on the DAG are not allowed by this kind of pass.
is_transformation_pass
Check if the pass is a transformation pass.
If the pass is a TransformationPass, that means that the pass can manipulate the DAG, but cannot modify the property set (but it can be read).
Methods
execute
execute(passmanager_ir, state, callback=None)
Execute optimization task for input Qiskit IR.
Parameters
- passmanager_ir (Any) – Qiskit IR to optimize.
- state (PassManagerState) – State associated with workflow execution by the pass manager itself.
- callback (Callable | None) – A callback function which is caller per execution of optimization task.
Returns
Optimized Qiskit IR and state of the workflow.
Return type
tuple[Any, qiskit.passmanager.compilation_status.PassManagerState]
name
run
run(dag)
Run the ApplyLayout pass on dag.
Parameters
dag (DAGCircuit) – DAG to map.
Returns
A mapped DAG (with physical qubits).
Return type
Raises
TranspilerError – if no layout is found in property_set or no full physical qubits.
update_status
update_status(state, run_state)
Update workflow status.
Parameters
- state (PassManagerState) – Pass manager state to update.
- run_state (RunState) – Completion status of current task.
Returns
Updated pass manager state.
Return type