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Control of electron dynamics in mesoscopic quantum circuits
Control of electron dynamics in mesoscopic quantum circuits
Future electronics faces a transition from conventional technology with progress predicted by Moore’s law to a quantum technology where quantum tunneling or coherent ballistic transport plays a significant role. This thesis concentrates on several applications of quantum technology. We start with demonstrating an alternative method for engineering the potential landscape in two-dimensional electron systems embedded in GaAs/AlGaAs heterostructures in the first chapter. We present a characterization of this design using field effect, Hall effect, and Aharonov- Bohm measurements to study electrostatic, dynamic and coherence properties and also show the general feasibility of our approach for future quantum applications. In the second chapter, we examine optimization of the electron transport between two distant quantum point contacts. We present a technique to measure the angular distribution of electrons emitted from a quantum point contact by deflecting it with an external magnetic field. In the second chapter, we also demonstrate coupling enhancement between two distant quantum point contacts by electrostatic focusing of ballistic electrons. Our observations favor electron dynamics according to a Gaussian beam optics model assuming Hermite functions rather than the frequently used plane electron wave model. In the third chapter, we discuss the coherent coupling of a quantum point contact with an open hemispherical resonator. We present a method to determine the electron phase coherence length based on Gaussian-Hermite modes of both quantum point contact and a cavity. Finally, the last chapter introduces a Lissajous rocking ratchet realized in the quantum dot embedded in the semiconductor heterostructure. It creates directed motion of electrons and breaks time-reversal symmetry on-chip. At the end of the thesis, we discuss results of performed experiments in the context of quantum technology.
quantum circuits, transport measurements, semiconductors, electronics, low-temperature physics
Platonov, Sergey
2017
English
Universitätsbibliothek der Ludwig-Maximilians-Universität München
Platonov, Sergey (2017): Control of electron dynamics in mesoscopic quantum circuits. Dissertation, LMU München: Faculty of Physics
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Abstract

Future electronics faces a transition from conventional technology with progress predicted by Moore’s law to a quantum technology where quantum tunneling or coherent ballistic transport plays a significant role. This thesis concentrates on several applications of quantum technology. We start with demonstrating an alternative method for engineering the potential landscape in two-dimensional electron systems embedded in GaAs/AlGaAs heterostructures in the first chapter. We present a characterization of this design using field effect, Hall effect, and Aharonov- Bohm measurements to study electrostatic, dynamic and coherence properties and also show the general feasibility of our approach for future quantum applications. In the second chapter, we examine optimization of the electron transport between two distant quantum point contacts. We present a technique to measure the angular distribution of electrons emitted from a quantum point contact by deflecting it with an external magnetic field. In the second chapter, we also demonstrate coupling enhancement between two distant quantum point contacts by electrostatic focusing of ballistic electrons. Our observations favor electron dynamics according to a Gaussian beam optics model assuming Hermite functions rather than the frequently used plane electron wave model. In the third chapter, we discuss the coherent coupling of a quantum point contact with an open hemispherical resonator. We present a method to determine the electron phase coherence length based on Gaussian-Hermite modes of both quantum point contact and a cavity. Finally, the last chapter introduces a Lissajous rocking ratchet realized in the quantum dot embedded in the semiconductor heterostructure. It creates directed motion of electrons and breaks time-reversal symmetry on-chip. At the end of the thesis, we discuss results of performed experiments in the context of quantum technology.