Berlin 2015 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 103: Transport: Poster Session

TT 103.52: Poster

Thursday, March 19, 2015, 15:00–18:00, Poster B

Correlations of weak measurements in a non-Markovian detection scheme — •Johannes Buelte¹, Adam Bednorz², and Wolfgang Belzig¹ — ¹Fachbereich Physik, Universität Konstanz, D-78457, Germany — ²Faculty of Physics, University of Warsaw, Hoza 69, PL-00681 Warsaw, Poland

Generalized quantum measurement schemes are described by positive operator-valued measures going beyond the projection postulate, which predicts the instantaneous collapse of the systems wave function. This allows to take the noninvasive limit and investigate the correlations of such weak measurements. We propose a scheme in which the detector is coupled to the measured system for a finite time, as it is the case in many real setups. This leads to non-Markovian effects, in accordance to the previous conjectures [1]. For the measured correlations this scheme predicts memory functions, which are related to symmetric and antisymmetric correlators of the detector variables. We investigate the memory functions under different general assumptions: (a) equilibrium detectors, (b) relation to the linear response Kubo formalism, (c) the role of non-equilibrium detectors and how they could realize the standard Markovian measurement. The latter scheme leads to the symmetrized operator order (aka Keldysh ordering), which is widely used in quantum measurement discussions.

[1] A. Bednorz , C. Bruder, B. Reulet, and W. Belzig,

Phys. Rev. Lett. 110, 250404 (2013)