Measurement back-action on adiabatic coherent electron transport

TL;DR

This paper investigates how a quantum point contact detector influences the adiabatic coherent transfer of electrons in a triple-well system, revealing measurement-induced effects and fidelity degradation.

Contribution

It introduces a numerical approach treating the entire system as a closed quantum system to analyze measurement back-action on CTAP.

Findings

Emergence of a new peak in electron passage distribution

Increased detector coupling reduces transfer fidelity

Single-realization measurement analysis is feasible

Abstract

We study the back-action of a nearby measurement device on electrons undergoing coherent transfer via adiabatic passage (CTAP) in a triple-well system. The measurement is provided by a quantum point contact capacitively coupled to the middle well, thus acting as a detector sensitive to the charge configuration of the triple-well system. We account for this continuous measurement by treating the whole {triple-well + detector} as a closed quantum system. This leads to a set of coupled differential equations for the density matrix of the enlarged system which we solve numerically. This approach allows to study a single realization of the measurement process while keeping track of the detector output, which is especially relevant for experiments. In particular, we find the emergence of a new peak in the distribution of electrons that passed through the point contact. As one increases the coupling between the middle potential well and the detector, this feature becomes more prominent and is accompanied by a substantial drop in the fidelity of the CTAP scheme.