Strong and weak coupling of two coupled qubits

I investigate the dynamics and power spectrum of two coupled qubits (two-level systems) under incoherent continuous pump and dissipation. New regimes of strong coupling are identified, which are due to additional paths of coherence flow in the system. Dressed states are reconstructed even in the regime of strong decoherence. The results are analytical and offer an exact description of strong coupling in the presence of pumping and decay in a nontrivial (nonlinear) system.