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arXiv:0907.2729 · Modern Physics Letters A

THE EFFECT OF RANDOM COUPLING COEFFICIENTS ON DECOHERENCE

MARIO CASTAGNINO, SEBASTIAN FORTIN, OLIMPIA LOMBARDI

Published Mar 14, 2010• 10 citations
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Abstract

The aim of this letter is to analyze the effect on decoherence of the randomness of the coupling coefficients involved in the interaction Hamiltonian. By studying the spin-bath model with computer simulations, we show that such randomness greatly improves the "efficiency" of decoherence and, then, its physical meaning deserves to be considered.

DOI
10.1142/s0217732310032196

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The aim of this letter is to analyze the effect on decoherence of the randomness of the coupling coefficients involved in the interaction Hamiltonian. By studying the spin-bath model with computer simulations, we show that such randomness greatly improves the "efficiency" of decoherence and, then, its physical meaning deserves to be considered.
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According to a usual reading, decoherence is a process resulting from the interaction between a small system and its large environment where information and energy are dissipated. The particular models treated in the literature on the subject reinforce this idea since, in general, the behavior of a particle immersed in a large "bath" composed by many particles is studied. The aim of this letter is to warn against this usual simplified reading. By means of the analysis of a well-known model, we will show that decoherence may occur in a system interacting with an environment consisting of only one particle.
The study of the decoherence of qubits in spin systems is almost restricted to environments whose constituents are spin-12\frac{1}{2}21​ particles. In this paper we consider environments that are composed of particles of higher spin, and we investigate the consequences on the dynamics of a qubit coupled to such baths via Heisenberg XYXYXY and Ising interactions. It is shown that, while the short time decay in both cases gets faster as the magnitude of the spin increases, the asymptotic behavior exhibits an improvement of the suppression of the decoherence when the coupling is through Heisenberg XYXYXY interactions. In the case of a transverse Ising model, we find that the mean-field approximation breaks down for high values of the spin.