Preserving quantum correlations and coherence with non-Markovianity

TL;DR

This paper demonstrates that non-Markovian quantum dynamics can effectively preserve correlations and coherence in open quantum systems, outperforming Markovian processes, with experimental validation using linear optics.

Contribution

It shows how non-Markovianity can be exploited to maintain quantum correlations and coherence over time, providing new insights for quantum information preservation.

Findings

Non-Markovianity helps preserve correlations at large times.

Non-Markovian evolution maintains quantum coherence in covariant qubit systems.

Experimental implementation confirms theoretical predictions.

Abstract

Open quantum systems exhibit a rich phenomenology, in comparison to closed quantum systems that evolve unitarily according to the Schr\"odinger equation. The dynamics of an open quantum system are typically classified into Markovian and non-Markovian, depending on whether the dynamics can be decomposed into valid quantum operations at any time scale. Since Markovian evolutions are easier to simulate, compared to non-Markovian dynamics, it is reasonable to assume that non-Markovianity can be employed for useful quantum-technological applications. Here, we demonstrate the usefulness of non-Markovianity for preserving correlations and coherence in quantum systems. For this, we consider a broad class of qubit evolutions, having a decoherence matrix separated from zero for large times. While any such Markovian evolution leads to an exponential loss of correlations, non-Markovianity can help to preserve correlations even in the limit $t \rightarrow \infty$. For covariant qubit evolutions, we also show that non-Markovianity can be used to preserve quantum coherence at all times, which is an important resource for quantum metrology. We explicitly demonstrate this effect experimentally with linear optics, by implementing the required evolution that is non-Markovian at all times.