Dynamics of a qubit coupled to a broadened harmonic mode at finite detuning

We study the dynamics of a symmetric two-level system strongly coupled to a broadened harmonic mode. Upon mapping the problem on to a spin-boson model with peaked spectral density, we show how analytic solutions can be obtained, at arbitrary detuning and finite temperatures, in the case of large Q-factors of the oscillator. One, two or more dominating oscillation frequencies of the two-level particle can be observed as a consequence of the entanglement with the oscillator. Our approximated analytical solution agrees well with numerical predictions obtained within the non-interacting blip approximation.