Jumptime unraveling of open quantum systems

In contrast to the standard unraveling of quantum master equations, where the stochastically evolving quantum trajectories are ensemble-averaged at specific times, we argue that quantum trajectories can as well be averaged at specific jump counts. The resulting jumptime-averaged quantum state then follows a discrete, deterministic evolution equation, with time replaced by the jump count. This jumptime evolution represents a trace-preserving quantum dynamical map if and only if the underlying quantum master equation does not exhibit dark states. In the presence of dark states, on the other hand, the jumptime-averaged state decays into the dark state and the jumptime evolution eventually terminates. Jumptime-averaged quantum states are operationally accessible in continuous measurement schemes, where quantum jumps are registered as “clicks" in the detector. Monitoring combined with the readout at jumptimes thus allows one to realize quantum channels that are characterized by the jumptime evolution.

Reference: C. Gneiting, A.V. Rozhkov, F. Nori, arXiv:2001.08929