Ternary metal oxide substrates for superconducting circuits

Abstract

Substrate material imperfections and surface losses are one of the major factors limiting superconducting quantum circuitry from reaching the scale and complexity required to build a practical quantum computer. One potential path towards higher coherence of superconducting quantum devices is to explore new substrate materials with a reduced density of imperfections due to inherently different surface chemistries. Here, we examine two ternary metal oxide materials, spinel (MgAl2O4) and lanthanum aluminate (LaAlO3), with a focus on surface and interface characterization and preparation. Devices fabricated on LaAlO3 have quality factors three times higher than those of earlier devices, which we attribute to a reduction in the interfacial disorder. MgAl2O4 is a new material in superconducting quantum devices, and even in the presence of significant surface disorder, it consistently outperforms LaAlO3. Our results highlight the importance of materials exploration, substrate preparation, and characterization for identifying materials suitable for high-performance superconducting quantum circuitry.