# Source code for qutip.qip.compiler.instruction

    from copy import deepcopy
    import numpy as np

    __all__ = ['Instruction']

    class Instruction():
        """
        The instruction that implements a quantum gate.
        It contains the control pulse required to implement the gate
        on a particular hardware model.

        Parameters
        ----------
        gate: :class:`.Gate`
            The quantum gate.
        duration: list, optional
            The execution time needed for the instruction.
        tlist: array_like, optional
            A list of time at which the time-dependent coefficients are
            applied. See :class:`.Pulse` for detailed information`
        pulse_info: list, optional
            A list of tuples, each tuple corresponding to a pair of pulse label
            and pulse coefficient, in the format (str, array_like).
            This pulses will implement the desired gate.

        Attributes
        ----------
        targets: list, optional
            The target qubits.
        controls: list, optional
            The control qubits.
        used_qubits: set
            Union of the control and target qubits.
        """
        def __init__(
                self, gate, tlist=None,
                pulse_info=(), duration=1):
            self.gate = deepcopy(gate)
            self.used_qubits = set()
            if self.targets is not None:
                self.targets.sort()  # Used when comparing the instructions
                self.used_qubits |= set(self.targets)
            if self.controls is not None:
                self.controls.sort()
                self.used_qubits |= set(self.controls)
            self.tlist = tlist
            if self.tlist is not None:
                if np.isscalar(self.tlist):
                    self.duration = self.tlist
                elif abs(self.tlist[0]) > 1.e-8:
                    raise ValueError("Pulse time sequence must start from 0")
                else:
                    self.duration = self.tlist[-1]
            else:
                self.duration = duration
            self.pulse_info = pulse_info

        @property
        def name(self):
            return self.gate.name

        @property
        def targets(self):
            return self.gate.targets

        @property
        def controls(self):
            return self.gate.controls