Measuring the degeneracy of discrete energy levels using a GaAs/AlGaAs quantum dot

TL;DR

This paper introduces an experimental method to measure quantum state degeneracies in energy spectra of quantum dots, utilizing detailed balance and precise tunnelling rate measurements, tested on GaAs/AlGaAs quantum dots with tunable degeneracies.

Contribution

The paper presents a novel technique for directly measuring degeneracies in quantum energy levels using time-resolved tunnelling in quantum dots.

Findings

Successfully measured degeneracies in quantum dot energy levels.

Demonstrated control of degeneracies with electric and magnetic fields.

Linked ground state degeneracy to excited state lifetimes.

Abstract

We demonstrate an experimental method for measuring quantum state degeneracies in bound state energy spectra. The technique is based on the general principle of detailed balance, and the ability to perform precise and efficient measurements of energy-dependent tunnelling-in and -out rates from a reservoir. The method is realized using a GaAs/AlGaAs quantum dot allowing for the detection of time-resolved single-electron tunnelling with a precision enhanced by a feedback-control. It is thoroughly tested by tuning orbital and spin-degeneracies with electric and magnetic fields. The technique also lends itself for studying the connection between the ground state degeneracy and the lifetime of the excited states.