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 ∼2μeV 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 μeV energy scale.
@article{arxiv.cond-mat/0408089,
title = {Voltage-Controlled Optics of a Quantum Dot},
author = {A. Högele and S. Seidl and M. Kroner and K. Karrai and R. J. Warburton and B. D. Gerardot and P. M. Petroff},
journal= {arXiv preprint arXiv:cond-mat/0408089},
year = {2012}
}