Semiconducting two-dimensional electron gases (2DEG) are one of the most important materials for nanoelectronic devices. E.g. InAs plays a prominent role due to the large spin-orbit interaction it contains. In the last few years, it has been possible to create near-surface InAs 2DEGs where the electron gas has high mobility, yet can be easily coupled to superconducting electrodes. The superconducting layer is usually grown in-situ after the growth of the heterostructures leading to strong coupling to the semiconductor layer. Recently we have shown, that we can fabricate high quality Josephson junction and that the current-phase relation of these junctions can be measured using superconducting resonators. These building block can be used to define Andreev qubits, where in the Josephson junctions only a few channel is formed using split gate electrodes and where the lowest lying two levels can serve as the 0 and 1 of the qubit. Moreover, by coupling two junctions by a short superconducting segment the junctions can hybridize and form a so-call Andreev molecule. The same system allows the coupling of two Andreev qubits in principle.

In this PhD work, the candidate will fabricate InAs 2DEG based heterostructures. The circuits will be characterized at low temperatures using DC and RF techniques. The research will be carried out in close collaboration with several international partner institutes.