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PadDelay(fill_very_end=True, schedule_idle_qubits=False)

Padding idle time with Delay instructions.

Consecutive delays will be merged in the output of this pass.

The ASAP-scheduled circuit output may become

q_0:Delay(160[dt]) ├──■──
q_1: ──────┤ X ├───────┤ X ├
           └───┘       └───┘

Note that the additional idle time of 60dt on the q_0 wire coming from the duration difference between Delay of 100dt (q_0) and XGate of 160 dt (q_1) is absorbed in the delay instruction on the q_0 wire, i.e. in total 160 dt.

See BlockBasePadder pass for details.

Create new padding delay pass.


  • fill_very_end (bool) – Set True to fill the end of circuit with delay.
  • schedule_idle_qubits (bool) – Set to true if you’d like a delay inserted on idle qubits. This is useful for timeline visualizations, but may cause issues for execution on large backends.



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.


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).



PadDelay.__call__(circuit, property_set=None)

Runs the pass on circuit.


  • circuit (QuantumCircuit) – the dag on which the pass is run.
  • property_set (PropertySet or dict or None) – input/output property set. An analysis pass might change the property set in-place.


If on transformation pass, the resulting QuantumCircuit. If analysis

pass, the input circuit.

Return type



Return the name of the pass.


Run the padding pass on dag.


dag (DAGCircuit) – DAG to be checked.


DAG with idle time filled with instructions.

Return type



TranspilerError – When a particular node is not scheduled, likely some transform pass is inserted before this node is called.

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