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Quantum dots: building blocks of quantum devices?

Bayer, Manfred, Ortner, G., Larionov, A., Yakovlev, D. R., Schwab, M., Borri, Paola, Langbein, Wolfgang Werner, Woggon, U., Yugova, I., von Hogersthal, G. B. G., Lyanda-Geller, Y. B., Reinecke, T. L., Fafard, S., Wasilewski, Z., Korkusinski, M., Hawrylak, P., Forchel, A. and Reithmaier, J. P. 2004. Quantum dots: building blocks of quantum devices? In: Kramer, Bernhard ed. Advances in Solid State Physics, Vol. 44. Berlin: Springer, pp. 191-211. (10.1007/978-3-540-39970-4_16)

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Among other systems quantum dots have been considered a's one of the prime candidates for a solid state quantum information processing that is scalable up to a large number of quantum bits. After some general considerations we focus here on an essential building block of a quantum processor, a quantum gate for entangling the states of two quantum bits. A pair of coupled quantum dots could be used for such gating purposes. To that effect we study the suitability of vertically correlated InAs/GaAs quantum dot pairs fabricated by self-assembly. The exciton photoluminescence shows a characteristic splitting of the quantum dot shells, which hints at a tunnel coupling of the dots. This coupling has been confirmed by fine structure studies, in which distinct anticrossings are observed in the magnetic field dispersion. These avoided crossings would not occur if the two dots were decoupled. By applying an electric field along the molecule axis we demonstrate that the molecule coupling can be controlled, which is a prerequisite for an entanglement creating interaction of controllable strength between quantum bits. However, four-wave mixing studies show a strong shortening of the exciton dephasing in the molecules as compared to quantum dots which appears to be problematic for application of excitons as the genuine bits in quantum information processing. Thus excitonic complexes with their possibility to be controlled by ultrashort laser pulses may be useful only as intermediate states in schemes, where the quantum storage rests on spin degrees of freedom, but for manipulating spin is swapped into charge in form of charged excitons.

Item Type: Book Section
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QC Physics
Publisher: Springer
ISBN: 3540211489
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Last Modified: 15 Apr 2020 13:15

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