Fix ElidePermutations pass in the presence of PermutationGates (backport #14603)
#14621
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mtreinish
approved these changes
Jun 16, 2025
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Summary
Fixes #14602.
Details and comments
The
ElidePermutationstranspiler pass removes swap gates and permutation gates from the circuit, tracking the current permutation of the qubits using the internal variablemapping. Previously, this mapping was not updated correctly in the presence of permutation gates, leading to incorrect output circuits and updates to the pass manager's property set (namely, to"virtual_permutation_layout").The correct update rule should be$$M [ Q [i] ] \leftarrow M [Q [ P[i] ] ]$$ for $i=1,\dots,k$ , where $M$ is the current mapping within the $Q$ is the set of qubits the permutation gate is defined on, and $P$ is the "permutation pattern" of the permutation gate (stating which qubits get mapped to positions $0$ , $1$ , etc. when the permutation gate is applied).
ElidePermutationspass,This is an automatic backport of pull request #14603 done by Mergify.