Helium-ion-beam-patterned YBCO Josephson junctions for microwave applications

Josephson junctions (JJs) are key building blocks in many modern quantum circuits and other technological applications. Embedded in microwave circuits one can realize e.g. qubits or parametric amplifiers. JJs constitute also the essential component in voltage standards and in superconducting quantum interferometers. The variety of these applications shows the large demand for JJs fabricated with high precision, quality, and flexibility. Additionally, a maximized operation regime with respect to temperature and magnetic fields is highly desirable, however many standard technologies such as aluminum-based JJs are severely limited in this regard. Recently developed Josephson junctions patterned in Yttrium-Barium-Copper-Oxide (YBCO) by a focused helium-ion-beam, on the other hand, are promising candidates for a flexible junction technology operating in Tesla-fields and at tens of K. Many details regarding the fabrication and optimization of helium-ion-JJs in YBCO films of varying thickness and stoichiometry are still poorly explored and understood. On our poster, we discuss our latest progress on extending the applicability range of YBCO helium-ion-JJs to film stoichiometries and film thicknesses beyond the state-of-the-art, as it is required for the application in quantum circuits.