  We propose a simple structure for stationary non-Markovian quantum chains in
the framework of collisional dynamics of open quantum systems. To this end, we
modify the microscopic Markovian system--reservoir model, consider multiple
collisions with each of the molecules with an overlap between the collisional
time intervals. We show how the equivalent Markovian quantum chain can be
constructed with the addition of satellite quantum memory to the system. We
distinguish quantum from classical non-Markovianity. Moreover, we define the
counts of non-Markovianity by the required number of satellite qubits and bits,
respectively. As the particular measure of quantum non-Markovianity the discord
of the satellite w.r.t. the system is suggested. Simplest qubit realizations
are discussed, and the significance for real system--environment dynamics is
also pointed out.
