(Poster) Stability induced by chaos and disorder in the time reversal focalization

HERNAN L. CALVO; HORACIO M. PASTAWSKI

Dresden

Congreso; 75th Annual Meeting of the Deutsche Physikalische Gesellschaft; 2011

Deutsche Physikalische Gesellschaft

The experimental procedure known as the time reversal mirror successfully achieves the focusing of a local excitation after its propagation through a chaotic or disordered medium. An initially localized pulse that becomes in a series of low amplitude reverberations is registered by a transducer that re-injects the signal in the reversetemporal order. This enables the focalization of the original pulse whose quality increases with the level of disorder in the system. We study the stability of this phenomenon against two irreversible processes: the escape in an open cavity, and a closed cavity under the effects of an external perturbation. Within a semiclassical approach in termsof time-dependent trajectories, the multiple reflections of the redundant registration yield a focalization signal that can be related with the Loschmidt echo amplitude. Both situations describe a Fermi Golden Rule regime, where the decay of the focalization is dominated by the perturbation strength. However, in the closed cavity this decaydiminishes with the Lyapunov exponent of the system. This counter-intuitive result is a form of the quantum Zeno effect, which provides a new interpretation of the remarkable stability of the experiments.