Polarization of a charge qubit strongly coupled to a voltage-driven quantum point contact

We study a charge qubit with level splitting epsilon, coupled to a quantum point contact driven by voltage V. In the limit of weak coupling, the qubit polarization shows cusps at epsilon=+/- eV. We show that, for stronger couplings, prominent peculiarities occur at fractions epsilon=+/- eV/2. Further increase of the coupling leads to a polarization corresponding to a pseudo Boltzmann distribution with an effective temperature similar to eV.