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dc.contributor.authorSokolovski, D.
dc.contributor.authorRusconi, S. 
dc.contributor.authorBrouard, S.
dc.contributor.authorAkhmatskaya, E.
dc.description.abstractImposing restrictions on the Feynman paths of the monitored system has in the past been proposed as a universal model-free approach to continuous quantum measurements. Here we revisit this proposition and demonstrate that a Gaussian restriction, resulting in a sequence of many highly inaccurate (weak) von Neumann measurements, is not sufficiently strong to ensure proximity between a readout and the Feynman paths along which the monitored system evolves. Rather, in the continuous limit, the variations of a typical readout become much larger than the separation between the eigenvalues of the measured quantity. Thus, a typical readout is not represented by a nearly constant curve, correlating with one of the eigenvalues of the measured quantity $\hat{A}$, even when decoherence or Zeno effect is achieved for the observed two-level system, and does not point directly to the system's final state. We show that the decoherence in a ``free'' system can be seen as induced by a Gaussian random walk with a drift, eventually directing the system towards one of the eigenstates of $\hat{A}$. A similar mechanism appears to be responsible for the Zeno effect in a driven system, when its Rabi oscillations are quenched by monitoring. Alongside the Gaussian case, which can only be studied numerically, we also consider a fully tractable model with a ``hard wall'' restriction and show the results to be similar.en_US
dc.description.sponsorshipMINECO, Fondo Europeo de Desarrollo Regional FEDER, Grant No. FIS2015-67161-P (MINECO/FEDER) (D.S.), MINECO Grant No. SVP-2014-068451 (S.R.), MINECO Grant No. MTM2013-46553-C3-1-P (E.A.), SGI/IZOSGIker UPV/EHU, i2BASQUE academic network,en_US
dc.rightsReconocimiento-NoComercial-CompartirIgual 3.0 Españaen_US
dc.subjectRestrictions on Feynman pathsen_US
dc.subjectweak von Neumann measurementsen_US
dc.subjectcontinuous limiten_US
dc.subjectZeno effecten_US
dc.subjectRabi oscillationsen_US
dc.titleReexamination of continuous fuzzy measurement on two-level systemsen_US
dc.journal.titlePHYSICAL REVIEW Aen_US

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Reconocimiento-NoComercial-CompartirIgual 3.0 España
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