Advanced manufacturing of superconducting tunnel junctions for quantum computing applications

Superconducting circuits are the leading approach to real-world quantum applications due to their scalability, controllability, and reproducibility. Unleashing their commercial potential requires extending qubit lifetimes as well as enabling manufacturing capabilities with high yield and high throughput. To enhance qubit performances, this project will move away from traditional materials, such as aluminium and its oxide, to materials with well controlled insulating materials and interface quality. To this end, the project aims to develop deposition for superconducting tunnel junctions using an CMOS compatible approach. Characterization at the James Watt Nanofabrication Centre, the Microwave and THz lab, and the Quantum Circuits Group (PI Weides) for extraction of key parameters, such as critical temperature, critical current density, Josephson inductance, will assess thin film quality and validate the deposition and patterning processes.
Qubit coherence is the key challenge. The better the coherence is, the fewer the errors and the greater the quantum advantage. The critical process factors for controlling decoherence are i) defect states within the tunnel barrier, and ii) surface and interface impurities on the superconducting leads. The important technical barrier we address is the reliable, accurate, reproducible high volume manufacture of high coherence superconducting circuits with transmon qubits and based on atomic layer deposition, offering great potential for producing very thin, conformal films with possible control of the thickness and composition of the films at the atomic level. The key instrument is a state-of-the-art cluster tool for work in quantum technologies, which is now tuned towards superconducting films for quantum computing.
The project will
- establish and optimize overlap tunnel junctions grown by sputter deposition
-Establish a key technology for scaling of quantum processors of interest to the whole community, so would result in high-impact publications and potentially new IP.
- Lay the ground-work for making more complex multi-layer superconducting circuits at the JWNC which would benefit the UK as whole