  There is generally no obvious evidence in any direct relation between photon
blockade and atomic coherence. Here instead of only illustrating the photon
statistics, we show an interesting relation between the steady-state photon
blockade and the atomic coherence by designing a weakly driven cavity QED
system with a two-level atom trapped. It is shown for the first time that the
maximal atomic coherence has a perfect correspondence with the optimal photon
blockade. The negative effects of the strong dissipations on photon statistics,
atomic coherence and their correspondence are also addressed. The numerical
simulation is also given to support all of our results.
