Source code for qiskit_ibm_provider.transpiler.passes.scheduling.pad_delay

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# (C) Copyright IBM 2022.
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"""Padding pass to insert Delay into empty timeslots for dynamic circuit backends."""

from qiskit.circuit import Qubit
from qiskit.circuit.delay import Delay
from qiskit.dagcircuit import DAGNode, DAGOutNode

from .block_base_padder import BlockBasePadder

[docs]class PadDelay(BlockBasePadder): """Padding idle time with Delay instructions. Consecutive delays will be merged in the output of this pass. .. code-block::python 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 .. parsed-literal:: ┌────────────────┐ 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 :class:`BlockBasePadder` pass for details. """ def __init__(self, fill_very_end: bool = True, schedule_idle_qubits: bool = False): """Create new padding delay pass. Args: fill_very_end: Set ``True`` to fill the end of circuit with delay. schedule_idle_qubits: 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. """ super().__init__(schedule_idle_qubits=schedule_idle_qubits) self.fill_very_end = fill_very_end def _pad( self, block_idx: int, qubit: Qubit, t_start: int, t_end: int, next_node: DAGNode, prev_node: DAGNode, ) -> None: if not self.fill_very_end and isinstance(next_node, DAGOutNode): return time_interval = t_end - t_start self._apply_scheduled_op(block_idx, t_start, Delay(time_interval, "dt"), qubit)