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TT: Fachverband Tiefe Temperaturen

TT 101: Transport - Poster Session

TT 101.29: Poster

Donnerstag, 3. April 2014, 15:00–19:00, P2

Non-Markovian noninvasive measurements in coupled quantum systems — •Johannes Buelte and Wolfgang Belzig — Fachbereich Physik, Universität Konstanz, D-78457, Germany

The standard textbook introduction of quantum measurement uses the projection postulate implying a instantaneous collapse of the systems wave function in the measurement process. In many real systems a less invasive measurement is performed by coupling a detector to the measured system for a finite time and with a weak interaction. We investigate the generalized measurement scheme by positive operator-valued measures (POVM) in the weak coupling limit with a focus on a non-Markovian interaction [1]. Such a scheme with memory allows to directly measure nonsymmetrized correlations and is hence related to absorption and emission noise. We calculate the memory function which couples the detector to the system in general and for a harmonic oscillator as detector and discuss the resulting quasiprobabilities, in particular the possible violation of weak positivity [2] by second-order correlation functions.
A. Bednorz , C. Bruder, B. Reulet, and W. Belzig, Phys. Rev. Lett. 110, 250404 (2013)
A. Bednorz and W. Belzig, Phys. Rev. B 83, 125304 (2011)