Defect-informed engineering for next-generation superconducting quantum technologies

Abstract:
Superconducting quantum processors are a leading platform for quantum computation. However, their scalability is fundamentally limited by dielectric loss arising from parasitic materials defects known as two-level systems (TLSs). Despite substantial progress in mitigating TLS-induced loss through improved fabrication, materials, and device design, further advances remain constrained by limited microscopic understanding of TLS origins and TLS-related dissipation mechanisms. In this talk, I will present a set of complementary efforts that use superconducting circuits and engineered environments to identify, probe, and engineer TLS-induced dissipation.
I will show the first atomistic identification of a bulk TLS bath relevant to superconducting circuits, originating from crystalline defects in silicon, and discuss implications for defect-targeted materials engineering. Additionally, I will discuss how phononic engineering can be used to control TLS dynamics. To further elucidate TLS-mediated decay pathways, I will present an experimental platform that probes single-defect–mediated electromechanical interactions. Across these studies, I will show how a microscopic understanding of defects and their interactions with engineered environments enables a defect-informed framework for realizing scalable superconducting quantum technologies.
Bio:
Dr. Zihuai Zhang is a postdoctoral scholar with Alp Sipahigil at Lawrence Berkeley National Laboratory, with a joint affiliation with the University of California, Berkeley. His research focuses on solid-state quantum devices, spanning spin qubits, superconducting circuits, and nanoscale electromechanical systems, with an emphasis on coherence engineering for scalable quantum technologies. He received his Ph.D. in Electrical and Computer Engineering from Princeton University in 2022, advised by Nathalie de Leon, and his B.S. in Physics from the University of Science and Technology of China in 2016.
Title: Postdoctoral scholar
Affiliation: Lawrence Berkeley National Laboratory & University of California, Berkeley