Catching and reversing quantum jumps and thermodynamics of quantum trajectories

Abstract

A recent experiment by Minev et. al [arXiv:1803.00545] demonstrated that in a dissipative (artificial) 3-level atom with strongly intermittent dynamics it is possible to "catch and reverse" a quantum jump "mid-flight": 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. Dark periods are thus like space-time bubbles of the inactive phase 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 to stabilise a desired dynamical phase 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.

Driving quantum systems with repeated conditional measurements

“…Similar experiments can be found in [11][12][13][14]. These form remarkable demonstration of quantum trajectory concepts [15][16][17][18][19][20][21][22][23][24][25]. More recently the interplay between unitary dynamics and measurements have been emphasized [26][27][28][29][30], in the context of quantum computing.…”

“…Using Eqs. ( 17) and (22), for the eigenstates of Ŝ that correspond to the eigenvalues that lie in the unit disk, i.e., 0<|ξ|<1, when two ξs coalesce, both left and right eigenvectors become parallel. Thus we only have one eigenvector instead of two.…”

Thermodynamics of quantum-jump trajectories of open quantum systems subject to stochastic resetting

“…Inactive periods can be, in particular, considered as "time bubbles" of the inactive phase into the active one, as shown in Ref. [16]. The dynamics of the three-level system in the shelving configuration has been further shown in Refs.…”

“…Note, that the large deviation statistics of the activity for a non-Markovian dynamics has previously been exactly computed in Ref. [16] for a different protocol, where a control-feedback mechanism applied to single quantum trajectoriesspoiling the Markovian character of the dynamics -is superimposed to a Lindbladian master equation evolution.…”

“…Namely, we consider a driven two-level atom subject to incoherent decay, as in Fig. 1, and a three-level system, which can show intermittency [9,12,16,62] in the recorded emissions. In both the cases we establish stochastic resetting as a valuable tool to analyze and tailor the dynamical activity of the system depending on the resetting time scale and on the chosen reset state.…”