Linking localization effects on the dynamic behavior of many-spin systems with quantum irreversibility

F.S. LOZANO NEGRO, A. DALLALBA, A. ZWICK; GONZALO A. ALVAREZ

Buenos Aires

Taller; IV Taller de Resonancia Magnética; 2018

Understanding the dynamics of complex quantum systems, ubiquitous in condensed matter physics and in large molecules like proteins, is an outstanding problem in physics. It contains several non-intuitive effects leading to many open questions, in particular, related to localization effects, non-thermalization and irreversibility of these dynamics.A new kind of phase transition has been observed in the coherent dynamical behavior of a 3D many-body quantum system1. It has been experimentally evidenced through quantum simulations using nuclear magnetic resonance (NMR) on a solid-state system1-3. A sudden quench on the interaction Hamiltonian dynamically induces correlations on the initially uncorrelated spins. The cluster-size of the correlated spins grows indefinitely as a function of time, and therefore, the spatial extension of the corresponding quantum superpositions that describes the states. Depending on the quench strength, a phase transition on the dynamical behavior is manifested leading to a localized dynamics for quench strengths lower than a critical value.In this work, we study the link between these dynamical localization effects and the possibility of time-reversing the spin dynamics by simulating the evolution of linear-chain spin- systems under a perturbed double quantum Hamiltonian and then refocusing the evolution by a non-perturbed double quantum Hamiltonian. We analyze the echo obtained like a measure of the decoherence of the system and we compare the simulations with the experiment?s results.References:1- G. A. Álvarez, D. Suter, and R. Kaiser, Science 349, 846 (2015).2- G. A. Álvarez and D. Suter, Phys. Rev. Lett. 104, 230403 (2010).3- G. A. Álvarez and D. Suter, Phys. Rev. A 84, 012320 (2011).