Dresden 2026 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 43: Superconducting Electronics: Qubits

TT 43.4: Talk

Wednesday, March 11, 2026, 10:15–10:30, CHE/0089

Niobium-based Josephson junctions for superconducting mm-wave qubits — •Urs Strobel¹, Benedict Rothmund¹, Jakob Lenschen¹, Jonas Kaemmerer¹, Lucas Radke¹, Sergei Masis¹, Jinji Luo-Hofmann³, Danny Reuter³, Hannes Rotzinger^1,2, and Alexey V. Ustinov^1,2 — ¹Physikalisches Institut (PHI), KIT, 76131 Karlsruhe, Germany — ²Institut for Quantum Materials and Technologies (IQMT), KIT, 76131 Karlsruhe, Germany — ³Fraunhofer-Institut für Elektronische Nanosysteme (ENAS), Chemnitz, Germany

Superconducting quantum circuits operating at millimeter-wave frequencies are an exciting area of research and offer the potential to maintain functionality at temperatures considerably higher than their widely studied centimeter-wave counterparts. The reduced wavelength allows for a smaller circuit footprint and faster qubit manipulation. Implementing such millimeter-wave qubits requires a superconductor with an energy gap above 100 GHz, which renders aluminum unsuitable. However, other conventional superconductors with larger gaps, such as niobium, are available with the technology to produce submicrometer Josephson junctions, key elements for superconducting quantum circuits.
To reduce dielectric losses, we use the low-loss substrate to eliminate extra dielectric layers present in classical niobium-based junction techniques [1]. We will present the concept, design constraints, and low-temperature characteristics. (2024)
[1] Patent pending DPO:02025132612.6 (2025)

Keywords: Josephson junction; mm-wave; superconducting qubit; niobium