# Non-Markovianity, coherence and system-environment correlations in a long-range collision model

## TL;DR

This paper explores how long-range interactions among environmental spins influence non-Markovian dynamics, quantum coherence decay, and system-environment correlations in a spin-based collisional model.

## Contribution

It introduces long-range and collective environmental interactions into a collisional model, revealing their impact on non-Markovianity and quantum coherence.

## Key findings

- Long-range environmental interactions increase non-Markovianity.
- Collective interactions further enhance non-Markovian effects.
- Non-Markovianity exhibits non-monotonic behavior with more environmental qubits.

## Abstract

We consider the dynamics of a collisional model in which both the system and environment are embodied by spin-$1/2$ particles. In order to include non-Markovian features in our model we introduce interactions among the environmental qubits and investigate the effect that different models of such interaction have on the degree of non-Markovianity of the system's dynamics. By extending that interaction beyond the nearest-neighbour, we enhance the degree of non-Markovianity in the system's dynamics. A further significant increase can be observed if a collective interaction with the forthcoming environmental qubits is considered. However, the observed degree of non-Markovianity in this case is non-monotonic with the increasing number of qubits included in the interaction. Moreover, one can establish a connection between the degree of non-Markovianity in the evolution of the system and the fading behaviour of quantum coherence in its state as the number of collisions grow. We complement our study with an investigation on system-environment correlations and present an example of their importance on a physical upper bound on the trace distance derivative.