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

We characterize highly coherent transmon qubits fabricated with a direct-write photolithography system. Multi-layer evaporation and oxidation allow us to change the critical current density by reducing the effective tunneling area and increasing the barrier thickness. Surface treatments before resist application and again before evaporation result in high-coherence devices. With optimized surface treatments, we achieve energy relaxation T1 times in excess of 80 μs for three dimensional transmon qubits with Josephson junction lithographic areas of 2 μm2.