MergeAdjacentBarriers

class qiskit.transpiler.passes.MergeAdjacentBarriers(*args, **kwargs)[source]

Bases: TransformationPass

Return a circuit with any adjacent barriers merged together.

Only barriers which can be merged without affecting the barrier structure of the DAG will be merged.

Not all redundant barriers will necessarily be merged, only adjacent barriers are merged.

For example, the circuit:

qr = QuantumRegister(3, 'q')
circuit = QuantumCircuit(qr)
circuit.barrier(qr[0])
circuit.barrier(qr[1])
circuit.barrier(qr)

Will be transformed into a circuit corresponding to:

circuit.barrier(qr[0])
circuit.barrier(qr)

i.e,

      ░  ░             ░  ░
q_0: ─░──░─      q_0: ─░──░─
      ░  ░             ░  ░
q_1: ─░──░─  =>  q_1: ────░─
      ░  ░                ░
q_2: ────░─      q_2: ────░─
         ░

after one iteration of the pass. These two barriers were not merged by the first pass as they are not adjacent in the initial circuit.

The pass then can be reapplied to merge the newly adjacent barriers.

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(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()

Name of the pass.

Return type:

str

run(dag)[source]

Run the MergeAdjacentBarriers pass on dag.

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:

PassManagerState