Decoherence during swapping operation

GONZALO A. ÁLVAREZ

Búzios, Brazil

Workshop; Pan American Advanced Studied Institute (PASI) and Workshop on Physics of Information - PASI 2003; 2003

Pan American Advanced Studied Institute

Seminario dictado acerca del poster "Decoherence during 1H-13C Cross-polarization" presentado en esta reunion. Resumen del Poster: As several of the Loschmidt echoes realizations using Nuclear Magnetic Resonance require polarization transfer steps, we have investigated the decoherence that occurs duiring the Cross-Polarization (CP) dynamics. A model for the quantum evolution of a coupled nuclear spin system 13C-1H connected to a reservoir is developed. The decoherence is introduced by stroboscopically (and then continously) stopping the quantum evolution. Polarization is injected to the system at each step of the interrupted evolution with certain probability. Excellent agreement with experimental data taken in molecular crystals is observed. It is remarkable that this simple model produces the exact result that can be obtained by reintroducing the neglected non-secular terms in the generalized Liouville-von Neumann approach introduced by Müller et al. [Phys. Rev. Lett. 32 (1974) 1402]. Thus, it is possible to establish the equivalence of these approaches and gain in the understanding of the physical significance of each contribution to the evolution, i.e., the part that produces dissipation and that inducing only decoherence.