Group seminar at MPQ and Zoom: Decoherence Channels in Fluxonium Qubits: Towards a Gradiometric Design

Vincent Koch, Walther-Meißner-Institute, Garching, Germany
Group seminar at MPQ lecture hall and Zoom
Tuesday, 05 August, 09:00am (MEZ)

Protecting qubits from decoherence remains one of the central challenges in building error-corrected quantum computers, which require coherence times exceeding strict thresholds. In this talk, I will explore the fluxonium circuit—a promising alternative to the widely used transmon—and analyze the mechanisms behind its dominant loss channels. Using the decay and dephasing rates induced by these effects, I will discuss how to select qubit parameter regimes that minimize coupling to these loss channels. Subsequently, I will describe the physical implementation of a fluxonium device using niobium and aluminum structures on a silicon chip. Furthermore, I will present experimental results on coherence times and parameter targeting, obtained from the sample produced in this work. This data allows us to identify the specific mechanisms limiting the performance of the device. Finally, I will propose a gradiometric fluxonium circuit and examine different implementations to significantly reduce the impact of homogeneous magnetic fields on the qubit.