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Fluxonium Qubits at 300mm wafer scale

NY CREATES is working together with Seeqc on an Air Force Research Laboratory (AFRL) funded Small Business Technology Transfer (STTR) project to develop fluxonium qubits at 300mm wafer scale. The team completed Phase I successfully in 2020, and was selected for a Phase II award during the AFRL Quantum Collider event in December 2020.

Fluxonium qubits (using aluminum/aluminum-oxide/aluminum junctions) have been recently shown by the Manucharyan group at University of Maryland to have superior characteristics in terms of “anharmonicity” (the relative spacing between energy levels) and coherence time. Fluxonium qubits designed by this group use long chains of Josephson junctions, with nearly a hundred per chain – hence making 300mm fabrication an ideal choice.

This project will demonstrate two world-firsts – the first demonstration of all-tantalum based Josephson junction, and the first demonstration of fluxonium qubits using such junctions and related circuit elements at 300mm scale. Recent work by Princeton has quantified the improvement in qubit coherence that is enabled by tantalum-based interconnect – which has been attributed to the simpler nature of the native oxide that is formed on tantalum, in contrast to niobium. The AFRL STTR project by Seeqc and NY CREATES aims to improve further, by fabricating and characterizing junctions in fluxonium qubits that use alpha-tantalum with a tunnel barrier of tantalum nitride. In addition, this project will implement and test fluxonium designs that leverage the unique ability of 300mm processes to deliver tightly controlled Josephson junctions, along with higher-Q damascene capacitors and other elements needed for quantum computing.