title: Dephasing by a zero-temperature detector and the Friedel sum rule.
abstract: Detecting the passage of an interfering particle through one of the interferometer's arms, known as "which path" measurement, gives rise to interference visibility degradation (dephasing). Here, we consider a detector at equilibrium. At finite temperature, dephasing is caused by thermal fluctuations of the detector. More interestingly, in the zero-temperature limit, equilibrium quantum fluctuations of the detector give rise to dephasing of the out-of-equilibrium interferometer. This dephasing is a manifestation of an orthogonality catastrophe, which differs qualitatively from Anderson's. Its magnitude is directly related to the Friedel sum rule.
authors.affiliation: Institut für Theoretische Physik, Universität Leipzig, D-04103, Leipzig, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Rosenow
authors.forename: Yuval
authors.initials: Y
authors.lastname: Gefen