y import qapply

        >>> c = H(0)*H(1)*Qubit('00')
        >>> c
        H(0)*H(1)*|00>
        >>> q = qapply(c)
        >>> measure_all(q)
        [(|00>, 1/4), (|01>, 1/4), (|10>, 1/4), (|11>, 1/4)]
    ra