increases, the contributions of the qubit-cavity interaction become dominant and the lost entanglement will be transferred quickly from the cavity to qubits with less revivals time, as shown in Fig \[dynamics GEM\] (a).

Moreover, it is significant to study the different behavior of the multipartite entanglement and the bipartite entanglement. The concurrence characterizes the entanglement between two qubits. Due to the symmetric Dicke states in the three-qubit collective model, the concurrence is evaluated in terms of the expectation values of the collective spin operators as $C=\max
\{0,C_{y},C_{z}\}$, where the quantity $C_{n}$ is defined for a given direction $n(=y,z)$ as $C_{n}=\frac{1}{2N(N-1)}\{N^{2}-4\langle
S_{n}^{2}\rangle -\sqrt{[N(N-2)+4\langle S_{n}^{2}\rangle
]^{2}-[4(N-1)\langle S_{n}\rangle ]^{2}}\}$ [@vidal]. From the dynamical wavefunction $|\phi (t)\rangle $, we can easily evaluate the coefficients for the qubit to remain in the $|j,m\rangle $ state $$\label{zeroprob}
P_{m}^{0th}=\sum_{n=0}^{\infty
}\sum_{k=1}^{4}f_{n}(t)e^{-iE_{n}^{k}t},$$in the zeroth-order approximation and $$\begin{aligned}
\label{probability}
P_{m}^{\mathtt{GRWA}} &\approx&\sum_{n}^{\infty
}\sum_{k=1}^{4}f_{n}^{k}(t)(e^{-iE_{n-2}^{k}t}+e^{-iE_{n-1}^{k}t}  \notag \\
&&+e^{-iE_{n}^{k}t}+e^{-iE_{n+1}^{k}t}),\end{aligned}$$in the GRWA. $f_{n}^{k}(t)$ is a dynamical parameter associated with the initial state and the $k$-th eigenstates for each $n$. From $P_{m}^{\mathtt{GRWA}}$ in Eq.( \[probability\]), we observe energy-level transitions among $E_{n-2}^{k}$, $E_{n\pm 1}^{k}$ and $%
E_{n}^{k}$ in the GRWA, which produce essential improvement of the dynamics over the zeroth-order ones in Eq.( \[zeroprob\]). Since the average 