Disentanglement in a two-qubit system subjected to dissipative environment: Exact analysis

We investigate the time evolution of entanglement of various entangled states of two-qubit atomic system in vacuum environment using exact analysis. Compared to our earlier work under Markov approximation [M. Ikram, F.-L. Li, M.S. Zubairy, Phys. Rev. A 75 (2007) 062336] we show that disentanglement rate is slower and sudden death times are higher than the earlier study in each set of entangled state.