  We investigate the dynamics of entanglement given by the concurrence of a
two-qubit system in the non-Markovian setting. A quantum master equation is
derived which is solved in the eigen basis of the system Hamiltonian for X-type
initial states. A closed formula for time evolution of concurrence is presented
for a pure state. It is shown that under the influence of dissipation that
non-zero entanglement is created in unentangled two qubit states which decay in
the same way as pure entangled states. We also show that under real
circumstances, the decay rate of concurrence is strongly modified by the
non-Markovinity of the evolution.
