def multiply(self, other):
        """Return the QuantumChannel self + other.

        Args:
            other (complex): a complex number.

        Returns:
            Kraus: the scalar multiplication other * self as a Kraus object.

        Raises:
            QiskitError: if other is not a valid scalar.
        """
        if not isinstance(other, Number):
            raise QiskitError("other is not a number")
        # If the number is complex we need to convert to general
        # kraus channel so we multiply via Choi representation
        if isinstance(other, complex) or other < 0:
            # Convert to Choi-matrix
            return Kraus(Choi(self).multiply(other))
        # If the number is real we can update the Kraus operators
        # directly
        val = np.sqrt(other)
        kraus_r = None
        kraus_l = [val * k for k in self._data[0]]
        if self._data[1] is not None:
            kraus_r = [val * k for k in self._data[1]]
        return Kraus((kraus_l, kraus_r), self._input_dim, self._output_dim)
Return the QuantumChannel self + other.

        Args:
            other (complex): a complex number.

        Returns:
            Kraus: the scalar multiplication other * self as a Kraus object.

        Raises:
            QiskitError: if other is not a valid scalar.