  We report the implementation of projective measurement on a single 1/2
nuclear spin of the 171Yb atom by measuring the polarization of cavity-enhanced
fluorescence. To obtain cavity-enhanced fluorescence having a
nuclear-spin-dependent polarization, we construct a two-mode cavity QED system,
in which two cyclic transitions are independently coupled to each of the
orthogonally polarized cavity modes, by manipulating the energy level of 171Yb.
This system can associate the nuclear spin degrees of freedom with the
polarization of photons, which will facilitate the development of hybrid
quantum systems.
