Dr. rer. nat. Frank Deppe

Courses and Dates

Offered Bachelor’s or Master’s Theses Topics

Charakterisierung des Prototyps für ein Quantum Local Area Network (Q-LAN)

Quantum technologies are on the verge of revolutionizing high-security communication owing to advanced protocols such as teleportation and remote-state preparation. Development of quantum local area networks (QLAN) is an important milestone in this field. Such a microwave QLAN can be realized as  superconducting transmission line cooled down to millikelvin temperatures.  In practice, this system requires careful characterization measurements with quantum signals propagating over the cryogenic link in order to determine the effective losses, noise level, and other imperfections.

In this work, the main goal is to investigate a new prototype of a quantum local area network (QLAN) established between two neighboring laboratories. This includes analysis of experimental results with theoretical and numerical methods. This project will provide you an excellent opportunity to gather expertise in a broad range of topics from quantum physics to microwave engineering and cryogenic techniques.

suitable as

• Master’s Thesis Condensed Matter Physics
• Master’s Thesis Applied and Engineering Physics
• Master’s Thesis Quantum Science & Technology

Supervisor: Frank Deppe

Herstellung von verlustarmen Josephson-Kontakten für Quanten-Bauelemente

Josephson junctions (JJs) represent a fundamental building block of modern quantum circuits such as superconducting qubits or Josephson parametric amplifiers. The JJs are conventionally fabricated with Al while the surrounding quantum circuits are often made of Nb. Henceforth, there is a need of galvanic connection between them which includes removing Nb oxide via ion milling.  As a consequence, one needs to develop a careful milling and fabrication technique in order to preserve a low-loss microwave environment in the close vicinity of JJs. This task is of paramount importance for achieving high coherence times of the related quantum devices.

The goal of this Master project is to develop a fabrication technique for Al/Nb superconducting circuits which will include Ar/O2 milling. This also includes cryogenic microwave studies of fabricated superconducting circuits (such as Josephson parametric amplifiers and transmon qubits) and participation in experiments towards quantum information processing with superconducting devices.

suitable as

• Bachelor’s Thesis Physics
• Master’s Thesis Condensed Matter Physics
• Master’s Thesis Applied and Engineering Physics
• Master’s Thesis Quantum Science & Technology

Supervisor: Frank Deppe

Kalibrierung von Frequenz und Nichtlinearität in einem Bose-Hubbard-System

Bose-Hubbard systems offer an intriguing opportunity of studying quantum driven-dissipative dynamics. Nowadays, these systems can be conveniently implemented by combining superconducting resonators with Josephson junctions. In order to successfully measure nonclassical effects in these systems, such as generation of antibunched light, one needs to accurately quantify their respective frequency range and nonlinearity strength. This goal can be achieved by cryogenic microwave measurements of a Bose-Hubbard dimer with superconducting quantum circuits and numerical modelling of the respective Hamiltonian. These two steps comprise the main body of the current master project. The successful project will potentially lead to a development of robust single-photon microwave sources and further exploration of quantum matter in the form of networks of nonlinear superconducting resonators.

suitable as

• Master’s Thesis Condensed Matter Physics
• Master’s Thesis Applied and Engineering Physics
• Master’s Thesis Quantum Science & Technology

Supervisor: Rudolf Gross

Langlebiger supraleitender Quantenspeicher in Hufeisengeometrie

Long-lived and easy-to-address quantum memories are essential elements in quantum computing and quantum communication. At the WMI, we have recently built such a device in a compact form by placing a superconducting transmon qubit inside a high-quality 3D cavity resonator (E. Xie et al., Appl. Phys. Lett. 112, 202601, 2018, https://arxiv.org/abs/1803.04711). In addition, we have started to investigate potentialy advantageous cavity geometries. In your thesis, you investigate and improve the memory life time based such a novel cavity design and attempt optimal control strategies for improved memory process fidelities.

suitable as

• Master’s Thesis Condensed Matter Physics
• Master’s Thesis Applied and Engineering Physics
• Master’s Thesis Quantum Science & Technology

Supervisor: Frank Deppe