Superconductor qubits typically use aluminum-aluminum oxide tunnel junctions to provide the non-linear inductance. Junctions with semiconductor barriers make it possible to vary the superconductor material and explore beyond aluminum. We use InAs semiconductor nanowires coated with thin superconducting shells of beta-Sn to realize transmon qubits. By tuning the Josephson energy with a gate voltage, we adjust the qubit frequency over a range of 3 GHz. The longest energy relaxation time, T1 = 27 microseconds, is obtained at the lowest qubit frequencies, while the longest echo dephasing time, T2 = 1.8 microseconds, is achieved at higher frequencies. We assess the possible factors limiting coherence times in these devices and discuss steps to enhance performance through improvements in materials fabrication and circuit design.
@article{arxiv.2508.04007,
title = {Transmon qubit using Sn as a junction superconductor},
author = {Amrita Purkayastha and Amritesh Sharma and Param J. Patel and An-Hsi Chen and Connor P. Dempsey and Shreyas Asodekar and Subhayan Sinha and Maxime Tomasian and Mihir Pendharkar and Christopher J. Palmstrøm and Moïra Hocevar and Kun Zuo and Michael Hatridge and Sergey M. Frolov},
journal= {arXiv preprint arXiv:2508.04007},
year = {2025}
}
Comments
Data and code available at https://zenodo.org/records/16732149