  The dynamics of two superconducting flux qubits coupled to each other and to
a common bath is discussed. We focus on the case in which the qubit-qubit
coupling strength dominates over the respective qubit transition frequencies.
We derive the master equation including collective effect by modeling the bath
as 1D open space in this ultra-strong coupling regime, and find that the
coupling greatly modifies both the coherent and the incoherent dynamics of the
system, giving rise to qualitatively different properties. By analyzing the
steady-state and the dynamics governed by the master equation, we show that
ground state entanglement and maximum coherence between the two qubits can be
induced by the environment alone. By employing in addition a single external
driving field, both the entangled anti-symmetric and symmetric collective
states can be populated and preserved with high fidelity. Similarly, entangled
states can be prepared using adiabatic passage techniques using two external
fields. Our results could find applications in entangling quantum gates and
quantum memories free from the decoherence.
