Catching and reversing quantum jumps and thermodynamics of quantum trajectories

TL;DR

This paper interprets the experimental ability to catch and reverse quantum jumps using large deviation theory, showing how controlled dynamics can stabilize desired quantum phases and eliminate intermittency in open quantum systems.

Contribution

It provides a theoretical framework using large deviation formalism to understand and control quantum jump phenomena and intermittency in open quantum systems.

Findings

Control pulses can stabilize specific dynamical phases.

Appropriate control removes intermittency in quantum trajectories.

Large deviation analysis explains phase coexistence in quantum dynamics.

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.