Optical direct write of Dolan-Niemeyer-bridge junctions for transmon qubits

Abstract

We characterize highly coherent transmon qubits fabricated with a direct-write photolithography system. Multi-layer evaporation and oxidation llow us to change the critical current density by reducing the effective tunneling area and increasing the barrier thickness. Surface treatments efore resist application and again before evaporation result in high-coherence devices. With optimized surface treatments, we achieve nergy relaxation T1 times in excess of 80 ls for three dimensional transmon qubits with Josephson junction lithographic areas of 2 lm2.