  Using the paradigm of information backflow to characterize a non-Markovian
evolution, we introduce so-called precursors of non-Markovianity, i.e.
necessary properties that the system and environment state must exhibit at
earlier times in order for an ensuing dynamics to be non-Markovian. In
particular, we consider a quantitative framework to assess the role that
established system-environment correlations together with changes in
environmental states play in an emerging non-Markovian dynamics. By defining
the relevant contributions in terms of the Bures distance, which is
conveniently expressed by means of the quantum state fidelity, these quantities
are well defined and easily applicable to a wide range of physical settings. We
exemplify this by studying our precursors of non-Markovianity in discrete and
continuous variable non-Markovian collision models.

Quantum Physics