  In order to achieve practical implementations of emerging quantum
technologies, it is important to have a firm understanding of the dynamics of
realistic quantum open systems. Master equations provide a widely used tool in
this regard. In this work, we first construct a master equation, valid for weak
system-environment coupling, which explicitly takes into account the impact of
preparing an initial system state from an equilibrium system-environment state
that has system-environment correlations. We then investigate the role of
initial system-environment correlations using this master equation for a system
consisting of many two-level atoms interacting with a common environment. We
show that, in general, due to the initial system-environment correlations
before a state preparation, the quantum state of the system can evolve at a
faster time-scale. Moreover, we also consider different initial state
preparations, and demonstrate that the influence of state preparations depends
on the initial states prepared. Our results can be of interest to many topics
based on quantum open systems where system-environment correlation effects have
been neglected before.
