Superconducting proximity and confinement in a two-dimensional electron gas

Abstract

This thesis investigates gate-defined quantum dots (QDs) in a two-dimensional electron gas as a minimal platform to explore Kitaev chain physics and zero-energy states. By coupling two QDs through Andreev bound states (ABS) induced in a planar Josephson junction, we realize and control coherent interactions such as Cooper pair splitting and elastic co-tunneling. The devices are fabricated using multi-layer electron-beam lithography, wet and dry etching, and thin-film deposition techniques. To characterize these systems, we employ both DC transport and radio-frequency (RF) reflectometry measurements. We demonstrate tunable dot-dot coupling over micrometer distances using gate voltages and magnetic flux, and access a "poor man’s Majorana" regime. Finally, we explore an isolated QD-ABS-QD system using RF gate reflectometry to resolve states without tunnelling probes, revealing parity-dependent behaviour limited by measurement sensitivity and quasiparticle poisoning. These results advance the control and understanding of hybrid mesoscopic devices and lay a foundation for future experiments with confined structures in hybrid systems.