qiskit.transpiler.preset_passmanagers.level_2_pass_manager
level_2_pass_manager(pass_manager_config)
Level 2 pass manager: medium optimization by initial layout selection and gate cancellation using commutativity rules.
This pass manager applies the user-given initial layout. If none is given, a search for a perfect layout (i.e. one that satisfies all 2-qubit interactions) is conducted. If no such layout is found, qubits are laid out on the most densely connected subset which also exhibits the best gate fidelitites.
The pass manager then transforms the circuit to match the coupling constraints. It is then unrolled to the basis, and any flipped cx directions are fixed. Finally, optimizations in the form of commutative gate cancellation and redundant reset removal are performed.
In simulators where coupling_map=None, only the unrolling and optimization stages are done.
Parameters
pass_manager_config (PassManagerConfig) – configuration of the pass manager.
Return type
PassManager
Returns
a level 2 pass manager.
Raises
TranspilerError – if the passmanager config is invalid.