Adiabatic Manipulation of a System Interacting with a Spin Bath

Abstract

The Stimulated Raman Adiabatic Passage, a very efficient technique for manipulating a quantum system based on the adiabatic theorem, is analyzed in the case where the manipulated physical system is interacting with a spin bath. The exploitation of the rotating wave approximation allows for the identification of a constant of motion, which simplifies both the analytical and the numerical treatment, which allows for evaluating the total unitary evolution of the system and bath. The efficiency of the population transfer process is investigated in several regimes, including the weak and strong coupling with the environment and the off-resonance. The formation of appropriate Zeno subspaces explains the lowering of the efficiency in the strong damping regime.

Adiabatically Manipulated Systems Interacting with Spin Baths beyond the Rotating Wave Approximation

“…It is worth concluding with two more comments concerning a comparison with the results reported in ref. [56]. First, since our second-order perturbation treatment is valid only in the weak coupling regime, we cannot obtain corrections in the strong coupling regime where a generalized quantum Zeno effect were predicted to occur.…”

“…This implies that, in a model involving RWA, the correction is zero, which is perfectly in agreement with the results of ref. [56] where the efficiency always exhibits a plateau in the weak coupling limit and up to the weak-intermediate coupling regime.…”

“…Our present study is an evolution of the earlier studyreported in ref. [56], where the system-bath interaction has been considered in the RWA. Here, in order to improve the analysis, we have also considered the effects of the counter-rotating terms.…”

“…The manipulation of spin defects in magnetic materials through adiabatic following-based techniques has recently been studied in the presence of their interaction with the surrounding spins [55]. Moreover, very recently, the effect of STIRAP processes on a system interacting with a spin bath has been theoretically analyzed under the assumptions that allow for the Rotating Wave Approximation (RWA) in the interaction between the three-state system and the spins in the environment [56]. This study has been developed through an evaluation of the unitary dynamics, despite the fact that master equations can also be derived for the spin environments [57][58][59].…”

“…In this paper, we extend the previous study in ref. [56]; we still exploit the unitary evolution of the universe but overcome the RWA in the system-environment interaction, which makes the physical model more realistic. In fact, while the RWA implies the conservation of the total number of excitations (a feature which has been extensively used in the previous analysis), it somehow excludes a variety of possible transitions.…”