  Qubit-qubit interactions can significantly boost quantum coherence times for
Bell states. The coherence-time-enhancements are however not monotonic and
there exists a phase where further increasing the interaction is unhelpful. A
resonator in a suggested circuit QED type implementation of the
Tavis-Cummings(Dicke) model, is shown to shift this transition point depending
on the number of loaded photons. This allows the resonator to amplify the
coherence enhancements in certain regimes. The interactions also induce unusual
collapse and revival type behavior for the entanglement dynamics. A new and
exact open quantum systems formalism -- the quasi-Hamiltonians for the Dicke
model thus reveals how a Bell state in a resonator can be protected against
$1/f$ noise from randomly fluctuating two level systems. Simple circuit level
details are given for flux qubits.
