Vendredi 03 mai 2013 à 14h15
Auditoire Stueckelberg, Ecole de Physique
Weak Measurements in Quantum Transport and Beyond
Wolfgang Belzig, University of Konstanz
The difficulty in measuring non-commuting quantum mechanical observables is one of the most fascinating consequences of the quantum mechanical postulates, relevant for correlation measurements of the electric current . Hence, the investigation of quantum measurement and projection is a fundamentally interesting topic. We study the concept of weak measurement of non-commuting observables using a quasiprobabilistic description  relevant for mesoscopic transport experiments, resembling the Wigner function and other quasiprobabilities . The negativity of a quasiprobability can be tested by violation of classically derived inequalities. We discuss as first examples of such so-called quantum paradoxes an inequality violated by high-frequency fourth-order current cumulants in the quantum regime for experimentally feasible parameters . As second example we show how to detect nonlocal quantum correlations (entanglement) in mesoscopic junctions, which do not permit detection of single events .  A. Bednorz and W. Belzig, Phys. Rev. Lett. 101, 206803 (2008).  A. Bednorz and W. Belzig, Phys. Rev. B 81, 125112 (2010).  A. Bednorz, C. Bruder, B. Reulet and W. Belzig, arxiv:1211.6056.  A. Bednorz and W. Belzig, Phys. Rev. Lett. 105, 106803 (2010).  A. Bednorz and W. Belzig, Phys. Rev. B 83, 125304 (2011).