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Leon Koch

+49 89 289-14221
Page in TUMonline
Technical Physics

Offered Bachelor’s or Master’s Theses Topics

Fabrication of high-coherence superconducting qubits
Over the last two decades the coherence time of superconducting qubits, a leading platform in quantum computing, could be improved by five orders of magnitude from several nanoseconds up to hundreds of microseconds. However, for practical quantum computers further improvements of the qubits are required. In this project we will investigate different strategies to reproducibly fabricate Josephson junctions and junction arrays for different types of qubits. To go beyond the NISQ era, new fabrication techniques like surface passivation, post process treatments, optimal etching parameters and deposition conditions will be investigated to build highly coherent qubits with T1 times exceeding 100 µs. One line of research will focus on exploring the capability of operating superconducting qubits at higher microwave frequencies and the potential to overcome limits of current qubit technologies. New superconducting materials, such as rhenium, vanadium, indium, nitrides and other composite systems, will be employed that have a higher critical temperature than commonly used materials such as aluminum and niobium. Within this thesis, you will grow and optimize thin films of superconducting materials, design and fabricate high-frequency resonators and qubits, and characterize them at millikelvin temperatures with spectroscopic techniques. You will learn the process of superconducting circuit fabrication like photolithography, thin film deposition and reactive ion etching in our in-house cleanroom and you will learn how to control qubits with microwave pulses using an arbitrary waveform generator.
suitable as
  • Master’s Thesis Condensed Matter Physics
Supervisor: Stefan Filipp
Scaling and 3D integration of superconducting qubit devices
To build powerful quantum computers based on superconducting qubits, one has to face the challenge of a limited area on a planar chip to host an increasing number of qubits. Therefore, efforts to minimize the footprint per qubit and to provide scalable means to address and readout all qubits are key to further progress. The goal is to develop new fabrication and integration techniques such as superconducting air-bridges/crossover that add the third dimension to the usual 2D designs of quantum computers as well as through silicon vias (TSVs), small diameter holes through the silicon substrate that enable us to connect both sides of the chip as well as stacking several chips on top of each other. These additional degrees of freedom will enable us to implement advanced designs for qubits and resonators and increase the number of quantum circuits on a chip. During this project you will learn important nanofabrication techniques like photolithography, thin film deposition and reactive ion etching. You will also model and characterize superconducting quantum circuits.
suitable as
  • Master’s Thesis Condensed Matter Physics
Supervisor: Stefan Filipp
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