Berry phase due to quantum measurements

The usual, "static" version of the quantum Zeno effect consists in the hind rance of the evolution of a quantum systems due to repeated measurements. T here is however a "dynamic" version of the same phenomenon, first discussed by von Neumann in 1932 and subsequently explored by Aharonov and Anandan, in which a system is forced to follow a given trajectory. A Berry phase app ears if such a trajectory is a closed loop in the projective Hilbert space. A specific example involving neutron spin is considered and a similar situ ation with photon polarization is investigated.