Catching and reversing quantum jumps and thermodynamics of quantum trajectories

A recent experiment by Minev et al., arXiv:1803.00545 demonstrated that in a dissipative (artificial) three-level atom with strongly intermittent dynamics it is possible to ``catch and reverse'' a quantum jump ``midflight'': by the conditional application of a unitary perturbation after a fixed time with no jumps, the system was prevented from getting shelved in the dark state, thus removing the intermittency from the dynamics. Here we offer an interpretation of this phenomenon in terms of the dynamical large deviation formalism for open quantum dynamics. In this approach, intermittency is seen as the first-order coexistence of active and inactive dynamical phases (or more precisely, dynamical regimes in this finite level system). Dark periods are thus like time bubbles of the inactive regime in the active one. Here we consider a controlled dynamics via the (single---as in the experiment---or multiple) application of a unitary control pulse during no-jump periods. By considering the large deviation statistics of the emissions, we show that appropriate choice of the control allows one to stabilize a desired dynamical regime and remove the intermittency. In the thermodynamic analogy, the effect of the control is to prick bubbles, thus preventing the fluctuations that manifest phase coexistence. We discuss similar controlled dynamics in broader settings.