Material Defects Manipulation and Mitigation in Superconducting Qubits

Material loss in superconducting qubits has become a significant source of decoherence as the design and engineering of qubit circuits improved considerably. In particular, two-level system (TLS) defects, which are believed to be material defects residing in qubit circuit's ubiquitous oxides, lead to fluctuating reduction in qubit relaxation times (T1) that greatly affected the performance and stability of quantum processors. Here, I will introduce our ongoing works on manipulation of TLSs in superconducting qubits, both in-situ and ex-situ during the qubit measurement. By tuning TLSs in each qubit locally, we demonstrated increased qubit T1 stability and mitigation of loss that originated from TLSs. In parallel, our multidisciplinary effort across Berkeley Lab aimed to develop new capabilities to explore novel materials and their defect response in superconducting qubits, including cluster material growth chambers and high throughput qubit characterization using frequency-multiplexed Purcell-filtered three-dimensional transmons. Our work here established a multifaceted methodology to both understand the fundamental physics of TLS and mitigate their impact on superconducting qubits.