Marcel Franz – Quantum Matter Institute
Title: d-mon: an improved transmon qubit based on a cuprate Josephson junction

Abstract: Transmon qubit, based on a superconducting Josephson junction shunted by a large capacitance, is the workhorse component powering the majority of intermediate scale quantum computers currently in operation. I this talk I will describe a theoretical proposal for a novel transmon architecture dubbed “d-mon” that uses unconventional oxide superconductors and is designed to overcome one of the key shortcomings of the conventional transmon. The proposed d-mon architecture is based on a c-axis Josephson junction between a d-wave high-Tc cuprate and a conventional s-wave superconductor. Its chief advantage lies in the large and tunable anharmonicity of its energy spectrum that we predict should enable faster and more reliable gate operation. In contrast to some earlier cuprate-based qubit designs d-mon operates in the regime where quasiparticles are fully gapped and can be therefore expected to achieve long coherence times.

Speaker Bio: Marcel Franz is a Professor of Physics at The University of British Columbia and a Deputy Scientific Director of The Blusson Quantum Matter Institute. Franz is a leading expert in theories of topological quantum matter, unconventional superconductivity and strongly correlated electron systems. His group has made a number of significant advances in these fields including the recent prediction of high-temperature topological superconductivity in twisted bilayers of cuprate superconductors. Franz has received numerous awards and recognitions for his contributions including the A.P. Sloan Fellowship (2002), Killam Research Fellowship (2007), has been elected Fellow of the APS (2014) and The Royal Society of Canada (2022). He obtained his PhD at The University of Rochester in 1994 and worked as a postdoctoral fellow and McMaster and Johns Hopkins universities before joining the faculty of The University of British Columbia in 2000.