Zero temperature Dephasing and the Friedel Sum Rule

TL;DR

This paper explores how equilibrium quantum fluctuations at zero temperature cause dephasing in an interferometer, linking it to the Friedel sum rule and orthogonality catastrophe, distinct from thermal dephasing.

Contribution

It demonstrates that zero temperature equilibrium quantum fluctuations induce dephasing, revealing a novel connection to the Friedel sum rule and orthogonality catastrophe.

Findings

Zero temperature quantum fluctuations cause dephasing.

Dephasing magnitude relates to the Friedel sum rule.

Distinct from thermal dephasing mechanisms.

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 {\em 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.