The remaining negativities N versus the initial entanglement N 0 for a four-qubit system in the 3 × 10 4 random sampled pure states (gray solid dots), special states | Ψ 4 〉 (red solid lines) and | Φ 4 〉 (olive dashed lines) under the dephasing channel. We plot the remaining negativities characterizing robustness of the state when the dephasing noise p d = 1 / 8 , 2/8, 3/8, and 4/8 in panels (a), (b), (c), and (d), respectively. The same behavior is displayed for all other noise parameters and for systems with n=2,3,5,6, and 7.