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

Bases: BasePadding

Padding idle time with Delay instructions.

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

durations = InstructionDurations([("x", None, 160), ("cx", None, 800)])

qc = QuantumCircuit(2)
qc.delay(100, 0)
qc.x(1), 1)

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 BasePadding pass for details.

Create new padding delay pass.

  • fill_very_end – Set True to fill the end of circuit with delay.

  • target – The Target representing the target backend. If it supplied and it does not support delay instruction on a qubit, padding passes do not pad any idle time of the qubit.



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).



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.