Real-time detection of single electron tunneling using a quantum point contact

TL;DR

This paper demonstrates real-time detection of single electron tunneling events in a quantum dot using a nearby quantum point contact, achieving high temporal resolution limited by shot noise and measurement noise.

Contribution

It introduces a method for real-time, high-speed detection of individual electron tunneling events with a quantum point contact as a charge sensor.

Findings

Able to resolve tunnel events separated by 8 microseconds

Shot noise limits the detection timescale to 25 nanoseconds

QPC conductance changes by about 1% per electron transferred

Abstract

We observe individual tunnel events of a single electron between a quantum dot and a reservoir, using a nearby quantum point contact (QPC) as a charge meter. The QPC is capacitively coupled to the dot, and the QPC conductance changes by about 1% if the number of electrons on the dot changes by one. The QPC is voltage biased and the current is monitored with an IV-convertor at room temperature. We can resolve tunnel events separated by only 8 $\mu$s, limited by noise from the IV-convertor. Shot noise in the QPC sets a 25 ns lower bound on the accessible timescales.