On the emergence of quantum memory in non-Markovian dynamics

TL;DR

This paper investigates the conditions under which genuinely quantum memory arises in non-Markovian quantum dynamics, highlighting the role of reservoir initial entanglement and correlations in the transition from classical to quantum memory.

Contribution

It identifies physical conditions and provides criteria for the emergence of quantum memory in non-Markovian dynamics using the quantum homogenizer model.

Findings

Quantum memory depends on reservoir initial entanglement structure.

Interaction strength correlates with entanglement generation.

Physical criteria for quantum memory onset are established.

Abstract

The emergence of memory is a hallmark feature of non-Markovian dynamics. However, the type of memory -- classical or quantum -- required to realize certain dynamics remains unknown. We study the quantum homogenizer as a minimal model of non-Markovian evolution and identify the physical conditions under which genuinely quantum memory becomes necessary. Using entanglement measures and relying only on the local dynamics as a witness, we prove both analytically and numerically the type of memory depends not merely on the dynamics itself, but also on the reservoir's initial entanglement structure, and in particular the propagation of non-classical correlations within it. For different bi- or multi-partite reservoir initializations, we establish a correspondence between interaction strength and entanglement generation. We provide physical criteria and an activation lower bound for the onset of quantum memory. The results may inform us how environmental correlations govern the transition from classical to quantum memory in open quantum systems.