Impact of Josephson junction materials on the performance of superconducting qubits

Superconducting qubits are a leading modality for quantum computing, offering a favorable balance between coherence, gate times, scalability, and fidelity. I will explore the interplay between materials science and qubit performance, with a particular focus on how the materials used in Josephson junctions (JJs) affect qubit behavior. The frequency of a qubit is largely determined by the properties of JJs, which typically consist of amorphous oxide tunnel barriers. These barriers are also the likely location of most two-level systems (TLS) defects. Recently, we discovered an Alternating-Bias Assisted Annealing (ABAA) process that enables us to fine-tune JJs to achieve the desired frequency. Characterizing these ABAA post-processed JJs provides insight into the structural and chemical bonding uniformity of the amorphous oxides after ABAA processing, as well as the impact on qubit performance and TLS density.