The Loschmidt echo as a robust decoherence quantifier for many-body systems

PABLO ZANGARA; AXEL D. DENTE; PATRICIA R. LEVSTEIN; HORACIO M. PASTAWSKI

PHYSICAL REVIEW A - ATOMIC, MOLECULAR AND OPTICAL PHYSICS

AMER PHYSICAL SOC

Lugar: New York; Año: 2004

1050-2947

"The Loschmidt echo as a robust decoherence quantifier for many-body systems".  http://arxiv.org/abs/1111.2004We employ the Loschmidt Echo, i.e. the signal recovered after the reversal of an evolution, toidentify and quantify the processes contributing to decoherence. This procedure, which has beenextensively used in single particle physics, is here employed in a spin ladder. The isolated chainshave 1/2 spins with XY interaction and their excitations would sustain a one-body like propagation.One of them constitutes the controlled system S whose reversible dynamics is degraded by theweak coupling with the uncontrolled second chain, i.e. the environment E. The perturbative SEcoupling is swept through arbitrary combinations of XY and Ising like interactions, that containthe standard Heisenberg and dipolar ones. Different time regimes are identified for the LoschmidtEcho dynamics in this perturbative configuration. In particular, the exponential decay scales as aFermi golden rule, where the contributions of the different SE terms are individually evaluated andanalyzed. Comparisons with previous analytical and numerical evaluations of decoherence basedon the attenuation of specific interferences, show that the Loschmidt Echo is an advantageousdecoherence quantifier at any time, regardless of the S internal dynamics.