  According to the quantum Zeno effect, the frequent observations of a system
can dramatically slow down its dynamical evolution. We show that the Zeno
dynamics is the result of projective measurements among quantum states which
are indistinguishable. The physical time scale of the problem is provided by
the Cramer-Rao lower bound, which measure the distinguishability of states
along a path in the Hilbert space. We finally show that the Zeno dynamics with
particle entangled states might require quite smaller measurement intervals
than classically correlated states, and propose a realistic interferometric
experiment to test the prediction.
