zum Hauptkapitel Emerging Quantum Mechanics:


The found results can be interpreted in the usual decoherence picture: Due to entanglement with the environment the non-diagonal matrix elements of the density matrix vanish \cite{kiefer}.
In the case a) the qubit cannot collapse, because it is already in the ground state and it is not driven by a photon.

There remains the question why the coupling to the environment does not protect the eigenstates from coupling to the photon. The answer is that the photon couples to charge and charge is conserved. The charge will not vanish, if the eigenstates entangle to the environment. Therefore, even when entangled to the environment, the photon can still drive the current states between their two directions.