Electron Transport in Integrated Quantum Systems

In this thesis, integrated quantum devices defined using a split gate technique are studied experimentally. These integrated devices provide a novel platform to investigate the property of quantum systems, such as spin polarization, via non-local measurement. Information extracted from these integrated devices leads to a comprehensive understanding of the puzzling phenomenon such as the 0.7 anomaly. Meanwhile, these devices are possibly suitable for studying quantum entanglement because perturbation due to measurement is minimized in the non-local setup. Devices demonstrated here are also promising to be used as a building block such as quantum injector/detector or quantum bus (which is a information channel where quantum information can be transported coherently) for more complicated quantum systems. In the first experiment, a transverse electron focusing in n-type GaAs heterojunction is present where pronounced splitting of odd focusing peaks are observed. From the asymmetry of sub-peaks of the first focusing spin polarization is extracted directly, this provides direct evidence for intrinsic spin polarization in a quasi-one-dimensional system. Parameters which may affect transverse electron focusing are studied systemically. Changing the shape of the injector, thus tuning the adiabaticity of the injection process, can influence the presence of peak splitting or not, with the sharp (non-adiabatic) injector the peak splitting is absent while peak splitting is observed with the flat (adiabatic) injector. Adjusting the length of injector affects the spin polarization, the longer the channel the higher the spin polarization can be achieved. This highlights the role of exchange interaction which results in the spin polarization in the quasi-1D channel. Applying a dc source-drain bias leads to such a result, peak splitting is preserved with negative bias while it smears out with positive bias when the bias is above a particular value (0.5 mV in the experiment), this proves the existence of spin-gap. In the second experiment, the coupling between different quantum devices are investigated by using an integrated quantum device consisting of an QPC and electronic cavity, where the cavity is defined with the arc-shaped gate and an inclined reflector. Unique features such as the double-peak structure occurs in the 1D-2D transition regime of the arc-QPC and