Pure non-Markovian evolutions

TL;DR

This paper distinguishes between two classes of non-Markovian quantum evolutions, identifying pure non-Markovian dynamics as essential for information backflows and providing a framework to simulate noisy evolutions from pure ones.

Contribution

It introduces a classification of non-Markovian dynamics into noisy and pure types, and demonstrates how pure non-Markovian evolutions can be used to simulate noisy ones, advancing understanding of quantum memory effects.

Findings

Pure non-Markovian evolutions are essential for information backflows.

Noisy non-Markovian dynamics can be simulated from pure non-Markovian cores.

The framework applies to well-known dynamical models.

Abstract

Non-Markovian dynamics are characterized by information backflows, where the evolving open quantum system retrieves part of the information previously lost in the environment. Hence, the very definition of non-Markovianity implies an initial time interval when the evolution is noisy, otherwise no backflow could take place. We identify two types of initial noise, where the first has the only effect of degrading the information content of the system, while the latter is essential for the appearance of non-Markovian phenomena. Therefore, all non-Markovian evolutions can be divided into two classes: noisy non-Markovian (NNM), showing both types of noise, and pure non-Markovian (PNM), implementing solely essential noise. We make this distinction through a timing analysis of fundamental non-Markovian features. First, we prove that all NNM dynamics can be simulated through a Markovian pre-processing of a PNM core. We quantify the gains in terms of information backflows and non-Markovianity measures provided by PNM evolutions. Similarly, we study how the entanglement breaking property behaves in this framework and we discuss a technique to activate correlation backflows. Finally, we show the applicability of our results through the study of several well-know dynamical models.