1. Center for NanoScience and Sektion Physik, Ludwig-Maximilians-Universität, Geschwister-Scholl-Platz 1, 80539 München, Germany
2. School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, UK
3. Department of Physics and Astronomy, Ohio University, Athens, Ohio USA
4. Institute of Semiconductor Physics, Russian Academy of Sciences, Siberian Branch, 630090 Novosibirsk, Russia
5. Instituto de Microelectronica de Madrid, CNM-CSIC Isaac Newton, 8, PTM, 28760 Madrid, Spain
6. Materials Department, University of California, Santa Barbara, California 93106, USA

Correspondence to: Richard J. Warburton² Email: R.J.Warburton@hw.ac.uk

Abstract

The self-assembly of semiconductor quantum dots has opened up new opportunities in photonics. Quantum dots are usually described as 'artificial atoms', because electron and hole confinement gives rise to discrete energy levels. This picture can be justified from the shell structure observed as a quantum dot is filled either with excitons¹ (bound electron–hole pairs) or with electrons². The discrete energy levels have been most spectacularly exploited in single photon sources that use a single quantum dot as emitter^{3, 4, 5, 6}. At low temperatures, the artificial atom picture is strengthened by the long coherence times of excitons in quantum dots^{7, 8, 9}, motivating the application of quantum dots in quantum optics and quantum information processing. In this context, excitons in quantum dots have already been manipulated coherently^{10, 11, 12}. We show here that quantum dots can also possess electronic states that go far beyond the artificial atom model. These states are a coherent hybridization of localized quantum dot states and extended continuum states: they have no analogue in atomic physics. The states are generated by the emission of a photon from a quantum dot. We show how a new version of the Anderson model that describes interactions between localized and extended states can account for the observed hybridization.

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