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Soutenance de thèse

Vendredi 19 décembre à 14h00,
Salle Rémy Lemaire, K223

Orateur : Tobias BAUTZE
"Towards quantum optics experiments with single flying electrons in a solid state system"


This thesis contains the fundamental study of nano-electronic systems at cryogenic temperatures. We made use of ballistic electrons in a two-dimensional electron gas in a GaAs/AlGaAs heterostructure to form a real two-path electronic interferometer and showed how the phase of the electrons and hence their quantum state can be controlled by means of electrostatic gates. The device represents a promising candidate of a flying qubit. We developed a sophisticated numerical tight-binding model based on ballistic quantum transport, which reproduces all experimental findings and allows to gain profound knowledge about the subtle experimental features of this particular device. We proposed further measurements with this flying qubit system. With the ultimate goal of building a single electron flying qubit, we combined the single electron source that has been developed in our lab prior to this manuscript with an electronic beam splitter. The electrons are injected from static quantum dots into a train of moving quantum dots. This moving potential landscape is induced in the piezoelectric substrate of GaAs by surface acoustic waves from interdigial transducers. We studied and optimized all key components, which are necessary to build a single electron beam splitter and built up a reliable local fabrication process. The device is capable of studying electron interactions on the single electron level and can serve as a measurement platform for quantum optics experiments in electronic solid state systems. Finally, we developed a powerful tool capable of calculating the potential landscapes of any surface gate geometry, which can be used as a fast feedback optimization tool for device design and proposed an optimized prototype for the single electron beam splitter.

Key words : nano-electronics, quantum dot, single electron, surface acoustic wave (SAW), beam splitter, flying qubit ,electrostatic potential ,single electron source ,kwant, python, design optimization, tight-binding model

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