Complete positivity, finite-temperature effects, and additivity of noise for time-local qubit dynamics

Abstract

<p>We present a general model of qubit dynamics which entails pure dephasing and dissipative time-local master equations. This allows us to describe the combined effect of thermalization and dephasing beyond the usual Markovian approximation. We investigate the complete positivity conditions and introduce a heuristic model that is always physical and provides the correct Markovian limit. We study the effects of temperature on the non-Markovian behavior of the system and show that the noise additivity property discussed by Yu and Eberly [<a href="http://dx.doi.org/10.1103/PhysRevLett.97.140403">Phys. Rev. Lett. <b>97</b>, 140403 (2006)</a>] holds beyond the Markovian limit.</p>