Simplified Josephson-junction fabrication process for reproducibly high-performance superconducting qubits
Journal article, 2021

We introduce a simplified fabrication technique for Josephson junctions and demonstrate superconducting Xmon qubits with T1 relaxation times averaging above 50 μs (Q > 1.5 × 1 0 6). Current shadow-evaporation techniques for aluminum-based Josephson junctions require a separate lithography step to deposit a patch that makes a galvanic, superconducting connection between the junction electrodes and the circuit wiring layer. The patch connection eliminates parasitic junctions, which otherwise contribute significantly to dielectric loss. In our patch-integrated cross-type junction technique, we use one lithography step and one vacuum cycle to evaporate both the junction electrodes and the patch. This eliminates a key bottleneck in manufacturing superconducting qubits by reducing the fabrication time and cost. In a study of more than 3600 junctions, we show an average resistance variation of 3.7% on a wafer that contains forty 0.5 × 0.5-cm2 chips, with junction areas ranging between 0.01 and 0.16 μm2. The average on-chip spread in resistance is 2.7%, with 20 chips varying between 1.4% and 2%. For the junction sizes used for transmon qubits, we deduce a wafer-level transition-frequency variation of 1.7%-2.5%. We show that 60%-70% of this variation is attributed to junction-area fluctuations, while the rest is caused by tunnel-junction inhomogeneity. Such high frequency predictability is a requirement for scaling-up the number of qubits in a quantum computer.

qubits

Superconducting Resonators

Josephson Junctions

Author

Amr Osman

Chalmers, Microtechnology and Nanoscience (MC2), Quantum Technology

James Simon

Chalmers, Microtechnology and Nanoscience (MC2), Quantum Technology

Andreas Bengtsson

Chalmers, Microtechnology and Nanoscience (MC2), Quantum Technology

Sandoko Kosen

Chalmers, Microtechnology and Nanoscience (MC2), Quantum Technology

Philip Krantz

Administration MC2

Daniel Perez Lozano

Chalmers, Microtechnology and Nanoscience (MC2), Quantum Technology

Marco Scigliuzzo

Chalmers, Microtechnology and Nanoscience (MC2), Quantum Technology

Per Delsing

Chalmers, Microtechnology and Nanoscience (MC2), Quantum Technology

Jonas Bylander

Chalmers, Microtechnology and Nanoscience (MC2), Quantum Technology

Anita Fadavi Roudsari

Chalmers, Microtechnology and Nanoscience (MC2), Quantum Technology

Applied Physics Letters

0003-6951 (ISSN) 1077-3118 (eISSN)

Vol. 118 6 064002

Subject Categories

Atom and Molecular Physics and Optics

Other Physics Topics

Condensed Matter Physics

DOI

10.1063/5.0037093

More information

Latest update

3/18/2021