High-frequency methods gained importance and popularity in low-temperature solid-state experiments. They enable the fast characterization of nanodevices and give access to properties unattainable from transport measurements. In these schemes high-frequency resonators are coupled galvanically, capacitively or inductively to the investigated nanodevice. Reflection or transmission measurements on the resonator yield information about the coupled system. These methods are widely applied e.g. for high-fidelity, non-demolition readout of qubits, sensing the electronic density of states in 2D materials and probing the quantized level structure of quantum systems via two-tone spectroscopy. The systems which can be investigated vary from charge and spin qubits realized in semiconducting nanostructures to novel superconducting qubits based on hybrid semiconductor-superconductor structures.
Andreev levels emerge in a quantum dot coupled strongly to a superconducting electrode. If two quantum dots are coupled via a superconducting terminal, the quantum dots can hybridize and form an Andreev molecule. This novel state can be uniquely addressed by reflectometry measurements, where the absence of other electrodes guarantees sharp spectrum.
In this experimental research project, the applicant will create a measurement setup for high-frequency experiments based on tank circuits and superconducting resonators in a dilution refrigerator. The candidate will fabricate nanodevices using lithographical techniques, carry out and analyze low-temperature measurements on these devices.
Fluency in English
Strong background in solid-state physics
Experience in computer-controlled measurements
Motivation for experimental work