  We explicitly calculate information, fidelity, and reversibility of an
arbitrary single-qubit measurement on a completely unknown state. These
quantities are expressed as functions of a single parameter, which is the ratio
of the two singular values of the measurement operator corresponding to the
obtained outcome. Thus, our results give information tradeoff relations to the
fidelity and to the reversibility at the level of a single outcome rather than
that of an overall outcome average.
