def T1_sequence(length, target):
    """
    Generate a gate sequence to measure relaxation time in a two-qubit chip.

    Parameters
    ----------
    length : int
        Number of Identity gates.
    target : int
        Which qubit is measured.

    Returns
    -------
    list
        Relaxation sequence.

    """
    wait = ["Id"]
    prepare_1 = [f"rx90p[{str(target)}]"] * 2
    S = []
    S.extend(prepare_1)
    S.extend(wait * length)
    return S