Geometric Phase for Optical Free Induction Decay

Geometric phase is investigated for optical free induction decay with a modified Bloch equation by establishing in connecting density matrices with nonunit vector ray in a complex projective Hilbert space. Under the limiting of pure state, our approach may give out the Berry phase and Aharonov and Anandan one. Furthermore, by comparing our approach with the kinematic one, we find that, after a suitable modification to the kinematic approach, both differences are very small for the Berry phase of mixed states in the optical free induction decay under the case of quasicyclic evolution.