  The paper investigates the dynamics of entanglement and explores some
geometrical characteristics of the trajectories in state space, in four-qubit
Greenberger-Horne-Zeilinger (GHZ)-and W-type states, coupled to common and
independent classical random telegraph noise (RTN) sources. It is shown from
numerical simulations that: (i) the dynamics of entanglement depends
drastically not only on the input configuration of the qubits and the presence
or absence of memory effects, but also on whether the qubits are coupled to the
RTN in a CE or IEs; (ii) a considerable amount of entanglement can be
indefinitely trapped when the qubits are embedded in a CE; (iii) the CE
configuration preserve better the entanglement initially shared between the
qubits than the IEs, however, for W-type states, there is a period of time
and/or certain values of the purity for which, the opposite can be found.
Thanks to results obtained in our earlier works on the three-qubit model, we
are able to conclude that entanglement becomes more robustly protected from
decay when the number of qubits of the system increases. Finally, we find that
the trajectories in state space of the system quantified by the quantum Jensen
Shannon divergence (QJSD) between the time-evolved states of the qubits and
some reference states may be curvilinear or chaotic.
