Towards YBCO microwave quantum circuits for applications in high magnetic fields

Superconducting circuits with integrated Josephson Junctions (JJs) and superconducting quantum interference devices (SQUIDs) have led to a new era of quantum circuits in the past decades. In the microwave regime JJs and SQUIDs are used to implement nonlinear and tunable inductances for qubits, signal processing devices and quantum sensing. To date, the standard material for these devices is Aluminum (Al) due to its high quality and controllability with respect to design and fabrication of SIS JJs. Al, however, comes with the drawback of a low critical magnetic field, while many envisioned experiments require high fields up to the Tesla regime. The high-T_c superconductor Yttrium-Barium-Copper-Oxide (YBCO) can sustain fields >10 T and thus could be a promising solution for this problem, in particular when integrated with suitable JJs. Flux-tunable YBCO quantum circuits with favorable characteristics have been reported recently, but considerable improvements are still required before being truly useful for quantum applications. In this talk we report our progress towards high-quality Josephson quantum circuits fabricated from microwave-optimized YBCO films and integrated with helium-ion-beam-patterned Josephson junctions.