ElidePermutations

class qiskit.transpiler.passes.ElidePermutations(*args, **kwargs)

Bases: TransformationPass

Remove permutation operations from a pre-layout circuit

This pass is intended to be run before a layout (mapping virtual qubits to physical qubits) is set during the transpilation pipeline. This pass iterates over the DAGCircuit and when a SwapGate or PermutationGate are encountered it permutes the virtual qubits in the circuit and removes the swap gate. This will effectively remove any SwapGates or PermutationGate in the circuit prior to running layout. If this pass is run after a layout has been set it will become a no-op (and log a warning) as this optimization is not sound after physical qubits are selected and there are connectivity constraints to adhere to.

For tracking purposes this pass sets 3 values in the property set if there are any SwapGate or PermutationGate objects in the circuit and the pass isn’t a no-op.

original_layout: The trivial Layout for the input to this pass being run
original_qubit_indices: The mapping of qubit objects to positional indices for the state

of the circuit as input to this pass.
virtual_permutation_layout: A Layout object mapping input qubits to the output

state after eliding permutations.

These three properties are needed for the transpiler to track the permutations in the out QuantumCircuit.layout attribute. The elision of permutations is equivalent to a final_layout set by routing and all three of these attributes are needed in the case

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)

GitHub

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.