Ivan Tsitsilin

Courses and Dates

Offered Bachelor’s or Master’s Theses Topics

Dynamical decoupling and noise spectroscopy with superconducting qubits

The characterization and mitigation of decoherence sources in qubits is crucial for quantum computing applications. Decoherence of a quantum superposition state arises from the interaction between the system and the uncontrolled degrees of freedom in its environment. The qubit decoherence is characterized by two rates: a longitudinal relaxation rate Γ1 due to the exchange of energy with the environment, and a transverse relaxation rate Γ2 = Γ1/2 + Γϕ which contains the pure dephasing rate Γϕ. Irreversible energy relaxation can only be mitigated by reducing the amount of environmental noise, reducing the qubit’s internal sensitivity to that noise, or through multi-qubit encoding and error correction protocols. In contrast, dephasing is in principle reversible and can be refocused dynamically through the application of coherent control pulse methods. In this work we are going to investigate different sources of noise and decoherence and how dynamical-decoupling techniques such as CPMG can change the dephasing effects of low-frequency noise on a superconducting qubit.

suitable as

• Bachelor’s Thesis Physics

Supervisor: Stefan Filipp

Simulation and comparison of non-planar qubit architectures

Scalable designs of superconducting qubits are essential for the creation of large-scale multi-qubit processors used in quantum computers. Superconducting transmon qubits are described by their characteristic capacitance and the critical current of their Josephson-Junction. The capacitance of these qubits orginates from the geometry of the metal islands of the qubit on the chip surface. To accomodate for a large number of qubits and their respective control and readout lines new 3D integration methods have been developed over the last years, extending the superconducting structures beyond a single chip plane. In this work a number of these architectures will be simulated. The focus of this Bachelor thesis lies in the accurate simulation of these designs ranging over different orders of magnitude in size and the extraction of system paramerters from FEM solutions.

suitable as

• Bachelor’s Thesis Physics

Supervisor: Stefan Filipp