Monitoring quantum transport: Backaction and measurement correlations

TL;DR

This paper analyzes a quantum dot charge detection scheme, comparing classical and quantum models, revealing how measurement backaction influences electron localization and current, and establishing the classical approach's validity in most regimes.

Contribution

It introduces a comprehensive comparison between classical and quantum descriptions of quantum dot charge measurement, highlighting backaction effects and the conditions for classical approximation validity.

Findings

Classical correlations accurately predict measurement performance in most regimes.

Quantum backaction localizes electrons and reduces current.

Classical model parameters effectively describe quantum backaction effects.

Abstract

We investigate a tunnel contact coupled to a double quantum dot (DQD) and employed as charge monitor for the latter. We consider both the classical limit and the quantum regime. In the classical case, we derive measurement correlations from conditional probabilities, which yields quantitative statements about the parameter regime in which the detection scheme works well. Moreover, we demonstrate that not only the DQD occupation but also the corresponding current may strongly correlate with the detector current. The quantum mechanical solution, obtained with a Bloch-Redfield master equation, shows that the backaction of the measurement tends to localize the DQD electrons and, thus, significantly reduces the DQD current. Moreover, it provides the effective parameters of the classical treatment. It turns out that already the classical description is adequate for most operating regimes.