Exact Entanglement Dynamics Beyond the Rotating Wave Approximation
  The entanglement dynamics of two remote qubits is examined analytically. The qubits interact arbitrarily strongly with separate harmonic oscillators in the idealized degenerate limit of the Jaynes-Cummings Hamiltonian. In contrast to well known non-degenerate RWA results, it is shown that ideally degenerate qubits cannot induce bipartite entanglement between their partner oscillators. 
S. M. Hashemi Rafsanjani, S. Agarwal and J. H. Eberly
quant-ph physics.atom-ph