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 practicable 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 (MgAl 2 O 4 ) and lanthanum aluminate (LaAlO 3 ), with a focus on surface and interface characterization and preparation. Devices fabricated on LaAlO 3 have quality factors three times higher than earlier devices, which we attribute to a reduction in interfacial disorder. MgAl 2 O 4 is a new material in the realm of superconducting quantum devices and, even in the presence of significant surface disorder, consistently outperforms LaAlO 3 . Our results highlight the importance of materials exploration, substrate preparation, and characterization to identify materials suitable for high-performance superconducting quantum circuitry.

Effects of Laser-Annealing on Fixed-Frequency Superconducting Qubits

“…With this, we have put forth a model of local heating through the Si substrate. Additional studies with a change or etching of substrate underneath the JJ can help verify this model [43][44][45]. We have also demonstrated that laser-annealing is robust against aging, which is important for superconducting qubits since the time between laser-annealing and qubit measurement is nonnegligible.…”