  Understanding the dynamics of open quantum systems is a highly important task
for the implementation of emerging quantum technologies. To make the problem
tractable theoretically, it is common to neglect initial system-environment
correlations. However, this assumption is questionable in situations where the
system is interacting strongly with the environment. In particular, the system
state preparation can then influence the dynamics of the system via the
system-environment correlations. To gain insight into the effect of these
correlations, we solve an exactly solvable model of a quantum spin interacting
with a spin environment both with and without initial correlations for
arbitrary system-environment coupling strengths. We show that the effect of the
system state preparation may or may not be significant in the strong
system-environment coupling regime at low temperatures. We also study the
dynamics of the entanglement between two spins interacting with a common spin
environment with and without initial system-environment correlations to
demonstrate that the correlations can play a significant role in the dynamics
of two-qubit systems as well.
