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arXiv · 1405.6882

Pulsed and continuous measurements of exponentially decaying systems

Francesco Giacosa·Giuseppe Pagliara
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Abstract

We study the influence of a detector on the decay law of a quantum state whose "undisturbed" survival probability is purely exponential. In particular, we consider a detector with a finite energy band of detection, i.e. it interacts only with decay products having an energy within a certain range of values. In one case, we assume that the detector performs many repeated measurements at short time intervals in all of which a collapse of the wave function occurs (bang-bang or pulsed-type measurements). In the second case, we assume a continuous measurement which preserves unitarity. We confirm the slowing down of the decay in presence of a measuring apparatus, the Quantum Zeno effect, but the outcomes of the detector are in general qualitatively and quantitatively different in the two cases. In turn, this implies that the so-called Schulman relation (the equivalence of pulsed and continuous measurements) does not hold in general and that it is in principle possible to experimentally access how a certain detector performs a measurement.

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Francesco Giacosa, Giuseppe Pagliara. 2014-05-27. Pulsed and continuous measurements of exponentially decaying systems. https://doi.org/10.1103/physreva.90.052107

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