Regensburg 2016 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 37: Transport: Fluctuation and Noise
(Joint session of DY and TT organized by TT)

TT 37.6: Vortrag

Dienstag, 8. März 2016, 15:30–15:45, H23

Correlations of weak quantum measurements in a non-Markovian detection scheme — •Johannes Bülte¹, Adam Bednorz², Christoph Bruder³, and Wolfgang Belzig¹ — ¹Fachbereich Physik, Universität Konstanz, D-78457 Konstanz, Germany — ²Faculty of Physics, University of Warsaw, PL02-093 Warsaw, Poland — ³Department of Physics, University of Basel, CH-4056 Basel, Switzerland

Generalized quantum measurement schemes are described by positive operator-valued measures that go beyond the projection postulate, i.e., the instantaneous collapse of the systems’ wave function by the measurement. They allow to consider the noninvasive limit of so-called weak measurements, and, in particular, to investigate the correlations of several such measurements which permits the tracking of non-commuting observables. We propose a scheme in which the detectors are coupled to the measured system for a finite time which leads to non-Markovian effects [1]. We derive microscopic expressions for the memory functions which are related to the Kubo linear-response formalism. The deviations from the standard Markovian measurement with symmetrized operator order (Keldysh ordering) can be traced back to a detector-detector interaction mediated by the measured system. Finally, we discuss different detector types, and show that an appropriate choice enables e.g. the proof of the non-classical nature of a system by second-order correlation functions.
A. Bednorz, C. Bruder, B. Reulet, and W. Belzig,

PRL 110, 250404 (2013)