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Nonsymmetrized correlations in quantum noninvasive measurements
Adam Bednorz1, Christoph Bruder, Bertrand Reulet
1Faculty of Physics, University of Warsaw, ul. Hoża 69, PL00-681 Warsaw, Poland. abednorz@fuw.edu.pl
Physical Review Letters
|July 9, 2013
Summary
This study resolves operator ordering ambiguities in quantum current noise by integrating quantum weak-measurement theory. It reveals how detector properties influence noise measurements and their connection to electron state squeezing.
Area of Science:
- Quantum mesoscopic physics
- Quantum optics
- Condensed matter physics
Background:
- A persistent challenge in quantum mesoscopic physics involves determining the correct operator ordering for current noise expressions.
- Different operator orderings (symmetrized vs. nonsymmetrized) correspond to classical measurements versus quantum detectors sensitive to photon emission or absorption.
Purpose of the Study:
- To unify symmetrized and nonsymmetrized operator ordering schemes within a single theoretical framework.
- To investigate the role of detector properties and memory effects in quantum noise measurements.
- To explore the experimental implications of quantum weak-measurement theory for electron transport.
Main Methods:
- Development of a quantum weak-measurement theory incorporating memory effects via a memory function.
- Analysis of quasiprobabilities for various detector temperatures.
- Connection of theoretical predictions to experimentally measurable second-order correlation functions.
Main Results:
- Demonstration that both classical and quantum detector schemes can be embedded within the quantum weak-measurement framework.
- Characterization of quasiprobabilities and their potential negativity.
- Establishment of a link between quasiprobability negativity and the squeezing of many-body electron states.
Conclusions:
- The quantum weak-measurement theory provides a unified approach to understanding operator ordering in quantum current noise.
- The negativity of quasiprobabilities, detectable via correlation functions, is a signature of non-classical electron states in mesoscopic systems.
- Experimental verification is possible by observing electron state squeezing in ac-driven tunnel junctions.
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