Analysis of Ta-Re Alloys for Use in Superconducting Qubits

Abstract

Superconducting qubits are among the leading platforms for quantum computing, where material choice critically impacts qubit coherence and scalability. Tantalum (Ta) has emerged as a promising candidate due to its stable, self-limiting oxide Ta_2O_5, which hosts fewer dielectric two-level systems (TLS). Ta transmons on high-resist silicon exhibit lifetimes T_1 up to 1.68 ms and Q factors up to 2.5*10^7 \cite{bland2025}. Rhenium (Re) also forms an exceptionally thin and inert oxide layer, and has demonstrated resonator quality factors exceeding 2 * 10^6 \cite{crisa2025}. By alloying Ta with Re, we aim to combine Ta's low-loss coherence performance with Re's enhanced surface and structural properties. Ta--Re alloys may offer tailored superconducting behavior, improved oxidation resistance, and reduced TLS density---potentially surpassing pure Ta in coherence and fabrication resilience. This research explores the stability and oxidation behavior of thin-film Ta-Re alloys deposited on sapphire substrate.