Dynamics of coupled spins in the white- and quantum-noise regime

TL;DR

This paper analyzes the dynamics of coupled spins under different noise regimes, revealing how degeneracy points affect decoherence and providing analytic results for quantum noise effects at zero temperature.

Contribution

It offers new analytic insights into spin relaxation and decoherence in both white noise and quantum noise regimes, including effects near degeneracy points.

Findings

Decoherence is reduced near degeneracy points.

Purity decay slows down around degeneracy points.

Analytic form for one-phonon exchange contribution at zero temperature.

Abstract

We study the dynamics of dissipative spins for general spin-spin coupling. We investigate the population dynamics and relaxation of the purity in the white noise regime, in which exact results are available. Inter alia, we find distinct reduction of decoherence and slowdown of purity decay around degeneracy points. We also determine in analytic form the one-phonon exchange contribution to decoherence and relaxation in the ohmic quantum noise regime valid down to zero temperature.