  We constructed a cavity QED system with a diamagnetic atom of 171Yb and
performed projective measurements on a single nuclear spin. Since Yb has no
electronic spin and has 1/2 nuclear spin, the procedure of spin polarization
and state verification can be dramatically simplified compared with the pseudo
spin-1/2 system. By enhancing the photon emission rate of the 1S0-3P1
transition, projective measurement is implemented for an atom with the
measurement time of T_meas = 30us. Unwanted spin flip as well as dark counts of
the detector lead to systematic error when the present technique is applied for
the determination of diagonal elements of an unknown spin state, which is
delta|beta|^2 < 2 * 10^-2. Fast measurement on a long-lived qubit is key to the
realization of large-scale one-way quantum computing.
