Voltage-Controlled Optics of a Quantum Dot

TL;DR

This paper demonstrates voltage control of a single quantum dot's optical properties, revealing tunable excitonic states and the potential for quantum information applications, despite challenges from spectral fluctuations.

Contribution

It introduces a method to electrically control the optical properties of a quantum dot and explores the effects on excitonic states and exchange interactions.

Findings

Neutral exciton exhibits two narrow polarized lines.

Exchange interaction can be turned off with gate voltage.

Spectral fluctuations remain a challenge for manipulation.

Abstract

We show how the optical properties of a single semiconductor quantum dot can be controlled with a small dc voltage applied to a gate electrode. We find that the transmission spectrum of the neutral exciton exhibits two narrow lines with $\sim 2$ $\mu$eV linewidth. The splitting into two linearly polarized components arises through an exchange interaction within the exciton. The exchange interaction can be turned off by choosing a gate voltage where the dot is occupied with an additional electron. Saturation spectroscopy demonstrates that the neutral exciton behaves as a two-level system. Our experiments show that the remaining problem for manipulating excitonic quantum states in this system is spectral fluctuation on a $\mu$eV energy scale.