High-resolution error detection in the capture process of a single-electron pump

TL;DR

This paper demonstrates high-resolution detection of electron capture errors in a quantum dot using a quantum point contact sensor, achieving error probabilities as low as one in a million, crucial for quantum metrology.

Contribution

The study introduces a two-step measurement protocol to accurately detect rare electron capture errors in a quantum dot, enhancing understanding of charge capture dynamics for quantum metrology.

Findings

Errors occur in about 30 out of a million one-electron captures.

Two-electron capture errors are extremely rare, with only one error in over a million cycles.

Electron counting with QPC sensors effectively probes non-equilibrium charge dynamics.

Abstract

The dynamic capture of electrons in a semiconductor quantum dot (QD) by raising a potential barrier is a crucial stage in metrological quantized charge pumping. In this work, we use a quantum point contact (QPC) charge sensor to study errors in the electron capture process of a QD formed in a GaAs heterostructure. Using a two-step measurement protocol to compensate for $1/f$ noise in the QPC current, and repeating the protocol more than $10^{6}$ times, we are able to resolve errors with probabilities of order $10^{-6}$. For the studied sample, one-electron capture is affected by errors in $\sim30$ out of every million cycles, while two-electron capture was performed more than $10^6$ times with only one error. For errors in one-electron capture, we detect both failure to capture an electron, and capture of two electrons. Electron counting measurements are a valuable tool for investigating non-equilibrium charge capture dynamics, and necessary for validating the metrological accuracy of semiconductor electron pumps.