Seminar Date: Tuesday, January 27, 2026
Time: 11:00 AM PT
Location: 67-3111 & Zoom
Talk Title: Gap engineered – Asymmetric Josephson junctions for quantum information processing
Zoom recording (available for 30 days)
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Abstract:
Superconducting qubits based on Al/AlOx/Al Josephson junctions (JJs) have been the backbone of quantum computing research, owing to their reliable fabrication via double-angle shadow evaporation. However, these conventional devices remain vulnerable to quasiparticle tunneling and correlated error bursts induced by high-energy radiation, which pose a fundamental barrier to scalable fault-tolerant quantum computation. Addressing these challenges requires new approaches to junction design and material choice.
In this work, we introduce a novel approach to explore alternative JJ materials that enable gap engineering—a technique designed to suppress quasiparticle tunneling by creating an energy barrier across the junction. Using the Quantum Cluster system at the Molecular Foundry, we combine e-beam evaporation and sputter deposition to fabricate asymmetric JJ stacks with systematically varied superconducting gaps. In particular, we demonstrate Al/AlOx/NbN junctions, where the distinct asymmetry arising from the superconducting gaps of aluminum and Niobium Nitride act as a natural platform for robust gap engineering.
In this talk, we will discuss the fabrication process, material and qubit characterization results, and the broader implications of this approach for advancing superconducting qubit performance.
Bio:
Yashwanth Balaji obtained his Ph.D. in Electrical Engineering from KU Leuven and IMEC, Belgium in 2020, where his research focused on the fabrication and electrical characterization of 2D material–based transistors for next-generation electronic applications. He earned his M.Sc. in Nanoscience and Nanotechnology from KU Leuven in 2015 and holds a B.E. in Electronics and Instrumentation Engineering from Anna University, Chennai, India.
Following his Ph.D., Yashwanth worked as a Nanofabrication Engineer at Oxford Quantum Circuits (OQC) in the UK, where he led the delivery of superconducting quantum processing units. He is currently a Postdoctoral Researcher at the Molecular Foundry Nanofabrication Facility, focusing on material and device optimization for superconducting quantum circuits.
