Models of mesoscopic time-resolved current detection

TL;DR

This paper develops models for quantum detectors measuring time-resolved current in mesoscopic conductors, revealing quantum backaction effects on current correlations and predicting observable temperature, voltage, and frequency dependencies of higher-order cumulants.

Contribution

It introduces two models of quantum detectors for finite-frequency current measurements, highlighting backaction effects and providing concrete predictions for experimental verification.

Findings

Backaction leads to observable corrections in current correlations.

Environmental effects can be interpreted as quantum measurement backaction.

Predictions for temperature, voltage, and frequency dependence of the third cumulant.

Abstract

Quantum transport in mesoscopic conductors is essentially governed by the laws of quantum mechanics. One of the major open questions of quantum mechanics is what happens if non-commuting observables are measured simultaneously. Since current operators at different times do not commute, the high-frequency correlation functions of the current are realization of this fundamental quantum question. We formulate this problem in the context of measurements of finite-frequency current cumulants in a general quantum point contact, which are the subject to ongoing experimental effort. To this end, we present two models of detectors that correspond to a weak time-resolved measurement of the electronic current in a mesoscopic junction. In both cases, the backaction of the detector leads to observable corrections to the current correlations functions involving the so-called noise susceptibilities. As a result, we propose a reinterpretation of environmental corrections to the finite-frequency cumulants as inevitable effect resulting from basic quantum mechanical principles. Finally we make concrete predictions for the temperature-, voltage-, and frequency-dependence of the third cumulant, which could be verified directly using current experimental techniques.