def METHOD_NAME(w):
    """
    Convert an energy from unit mK to unit GHz.
    Parameters
    ----------
    w : float / array
        The energy in the old unit.
    Returns
    -------
    w_new_unit : float / array
        The energy in the new unit.
    """
    w_GHz = w * 1.0e-12 * (_kB / _h)
    return w_GHz