Quantum regression beyond the Born-Markov approximation for generalized spin-boson models

TL;DR

This paper investigates the validity of quantum regression beyond the Born-Markov approximation in generalized spin-boson models, demonstrating conditions under which quantum regression can be exactly satisfied.

Contribution

It analyzes CP-divisibility and quantum regression validity beyond standard approximations for a class of multi-level spin-boson models, showing how to engineer system-bath coupling for exact quantum regression.

Findings

Quantum regression can be exactly satisfied in certain generalized spin-boson models.

CP-divisibility analysis extends beyond the Born-Markov approximation.

Engineered system-bath coupling enables exact quantum regression.

Abstract

The quantum regression formula for an open quantum system consists in an infinite hierarchy of conditions for its multi-time correlation functions, thus requiring full access to the total "system+environment" evolution, and providing a stronger requirement than CP-divisibility. Here, we analyze CP-divisibility and check the validity of quantum regression beyond the Born-Markov approximation (e.g. weak coupling limit) for a class of generalized spin-boson (GSB) models giving rise to a multi-level amplitude-damping evolution; in all cases, it is possible to engineer the system-bath coupling in such a way that quantum regression is exactly satisfied.