Transmon qubit using Sn as a junction superconductor

Amrita Purkayastha; Amritesh Sharma; Param J. Patel; An-Hsi Chen; Connor P. Dempsey; Shreyas Asodekar; Subhayan Sinha; Maxime Tomasian; Mihir Pendharkar; Christopher J. Palmstrøm; Moïra Hocevar; Kun Zuo; Michael Hatridge; Sergey M. Frolov

arXiv · 2508.04007

Transmon qubit using Sn as a junction superconductor

Amrita Purkayastha·Amritesh Sharma·Param J. Patel·An-Hsi Chen·Connor P. Dempsey·Shreyas Asodekar·Subhayan Sinha·Maxime Tomasian·Mihir Pendharkar·Christopher J. Palmstrøm·Moïra Hocevar·Kun Zuo·Michael Hatridge·Sergey M. Frolov

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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.

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Amrita Purkayastha, Amritesh Sharma, Param J. Patel, An-Hsi Chen, Connor P. Dempsey, Shreyas Asodekar, Subhayan Sinha, Maxime Tomasian, Mihir Pendharkar, Christopher J. Palmstrøm, Moïra Hocevar, Kun Zuo, Michael Hatridge, Sergey M. Frolov. 2025-08-06. Transmon qubit using Sn as a junction superconductor. https://arxiv.org/abs/2508.04007

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