  We analyze a system of two qubits embedded in two different environments. The
qubits are coupled to each other and driven on-resonance by two external
classical sources. In the secular limit, we obtain exact analytical results for
the evolution of the system for several classes of two-qubit mixed initial
states. For Werner states we show that the decay of entanglement does not
depend on coupling. For other initial states with ``{\sf X}\rq\rq -type density
matrices we find that the sudden death time displays a rich dependence on the
coupling energy and state parameters due to the existence of processes of
delayed sudden birth of entanglement.

Quantum Physics;Mesoscale and Nanoscale Physics