Zooming in on Quantum Trajectories

Abstract

We propose to use the effect of measurements instead of their number to study the time evolution of quantum systems under monitoring. This time redefinition acts like a microscope which blows up the inner details of seemingly instantaneous transitions like quantum jumps. In the simple example of a continuously monitored qubit coupled to a heat bath, we show that this procedure provides well defined and simple evolution equations in an otherwise singular strong monitoring limit. We show that there exists anomalous observable localised on sharp transitions which can only be resolved with our new effective time. We apply our simplified description to study the competition between information extraction and dissipation in the evolution of the linear entropy. Finally, we show that the evolution of the new time as a function of the real time is closely related to a stable Levy process of index 1/2.

5 pages, 2 figures

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• Perturbation Theory for Weak Measurements in Quantum Mechanics, I -- Systems with Finite-Dimensional State Space
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• Stochastic spikes and Poisson Approximation of one-dimensional stochastic differential equations with applications to continuously measured Quantum Systems
• Continuous fuzzy measurement on two-level systems revisited
• The Open Quantum Brownian Motion and continual measurements
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• Continuous collapse models on finite dimensional Hilbert spaces
• To spike or not to spike: the whims of the Wonham filter in the strong noise regime