elif self.ados.exponents[k].type == BathExponent.types["-"]:
            if sign1 == -1:
                op = _data.mul(self._s_pre_minus_post_Qdag[k], -1j * sign2)
            else:
                op = _data.mul(self._s_pre_plus_post_Qdag[k], -1j * sign2)