  The origin of disentanglement for two specific sub-classes of $X$-states
namely maximally nonlocal mixed states (MNMSs) and maximally entangled mixed
states (MEMSs) is investigated analytically for a physical system consisting of
two spatially separated qubits interacting with a common vacuum bath. The
phenomena of entanglement sudden death (ESD) and the entanglement sudden birth
(ESB) are observed, but the characteristics of ESD and ESB are found to be
different for the case of two photon coherence and single photon coherence
states. The role played by initial coherence for the underlying entanglement
dynamics is investigated. Further, the entanglement dynamics of MNMSs and MEMSs
under different environmental noises namely phase damping, amplitude damping
and RTN noise with respect to the decay and revival of entanglement is
analyzed. It's observed that the single photon coherence states are more robust
against the sudden death of entanglement indicating the usability of such
states in the development of technologies for the practical implementation of
quantum information processing tasks.
