Transmon qubit using Sn as a junction superconductor

TL;DR

This paper demonstrates a transmon qubit using Sn as a superconductor in the junction, achieving tunable frequencies and notable coherence times, and discusses potential improvements for better performance.

Contribution

It introduces a novel superconductor-semiconductor hybrid transmon qubit with tunable frequency and coherence properties, expanding beyond traditional aluminum-based devices.

Findings

Maximum T1 relaxation time of 27 microseconds.

Maximum T2 dephasing time of 1.8 microseconds.

Frequency tuning range of 3 GHz.

Abstract

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.