Parts | Days | Selection | Search | Downloads | Help
TT: Fachverband Tiefe Temperaturen
TT 21: Transport: Fluctuations and Noise
TT 21.6: Talk
Tuesday, March 24, 2009, 15:45–16:00, HSZ 304
Time-Resolved Counting Statistics for a Quantum Point Contact — •Adam Bednorz1,2 and Wolfgang Belzig1 — 1Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany — 2Institute of Theoretical Physics, University of Warsaw, Hoza 69, 00-681 Warsaw, Poland
We show that the naive formulation of time-resolved full counting statistics fails for high frequencies and leads to results, which could be interpreted as negative probabilities. We propose to construct a properly time-ordered positive-operator-valued measure, that combines counting statistics with detector backaction parametrized by a characteristic time τ [1]. The standard counting statistics is recovered in long time limit. In high frequency limit, for a weak coupling between the system and detector, the generating functional of counting statistics gains an additional Gaussian white noise component, that saves the positivity of the probability. It agrees with experiments since otherwise at strong coupling the noise measurements would be considerably modified due to the detector backaction. Finally, we also show that with more than one detector these nonclassical correlations can be directly measured.
[1] A. Bednorz and W. Belzig, Phys. Rev. Lett. 101, 206803 (2008).