Performance Analysis of Superconductor-constriction-Superconductor Transmon Qubits

TL;DR

This paper computationally analyzes a superconducting transmon qubit with a superconductor-constriction-superconductor junction, showing improved charge dispersion but reduced anharmonicity, aiding design optimization.

Contribution

It introduces a Ginzburg-Landau theory-based framework for analyzing ScS transmon qubits, highlighting their advantages over traditional SIS designs.

Findings

Improved charge dispersion in ScS transmons.

Tradeoff of smaller anharmonicity compared to SIS.

Framework for estimating material properties and junction dimensions.

Abstract

This work presents a computational analysis of a superconducting transmon qubit design, in which the superconductor-insulator-superconductor (SIS) Josephson junction is replaced by a co-planar, superconductor-constriction-superconductor (ScS) nanobridge junction. Within the scope of Ginzburg-Landau theory, we find that the nanobridge ScS transmon has an improved charge dispersion compared to the SIS transmon, with a tradeoff of smaller anharmonicity. These calculations provide a framework for estimating the superconductor material properties and junction dimensions compatible with gigahertz frequency ScS transmon operation.