Dr. Kirill Fedorov

Courses and Dates

Offered Bachelor’s or Master’s Theses Topics

Breitbandiges dispersives Auslesen von supraleitenden Qubits

An essential step for implementation of quantum computing architectures is an efficient readout of qubits. In the field of superconducting quantum circuits, this is typically realized by dispersively coupling a superconducting qubit to a microwave resonator. Then, the frequency of the resonator depends on the state of the qubit. The former can be extracted by probing the resonator with a coherent  tone. However, efficiency of this readout approach is fundamentally limited by quantum  laws. The corresponding threshold is commonly known as the standard quantum limit and bounds quantum efficiency of the readout process by 50%. Nevertheless, recent investigations have shown that it is possible to circumvent this limit and reach quantum efficiency of the qubit readout of 100% by exploiting broadband readout signal combined with Josephson parametric amplifiers.

 

The goal of this Master project is to build a proof-of-principle experimental setup and perform microwave cryogenic measurements on a superconducting transmon qubit in the broadband regime in order to demonstrate violation of the standard quantum limit in the dispersive readout.

suitable as

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

Supervisor: Rudolf Gross

FPGA-basiertes Rückkopplungsverfahren für die Mikrowellen-basierte Quantenkommunikation

Quantum experiments often require fast and versatile data processing which allows for a quantum feedback operation. This approach opens the road to many fascinating experiments such as quantum teleportation, entanglement purification,  quantum error correction, among others. Here, we would like to develop a specific measurement and feedback setup, based on a field programmable gate array (FPGA), for experiments with propagating quantum microwaves.

The main goal is to program and experimentally test a specific image for an FPGA  which would allow for acquisition of microwave signals and feedback generation over few hundred of nanoseconds. This timescale is the prerequisite for exploiting quantum correlations effects for quantum communication and cryptography protocols with propagating squeezed microwaves which are conducted in our lab. This project will offer a deep insight into the state‑of‑the‑art FPGA devices, microwave measurements, and cryogenic experiments with superconductors.

suitable as

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

Supervisor: Rudolf Gross

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