Identification of soft modes in amorphous Al$_{2}$O$_{3}$ via first-principles

TL;DR

This study uses first-principles calculations to identify low-energy vibrational and electronic modes in amorphous Al$_{2}$O$_{3}$, shedding light on their potential role as two-level systems affecting qubit coherence.

Contribution

It is the first to analyze amorphous Al$_{2}$O$_{3}$ at the electronic and phononic level to identify modes linked to TLSs.

Findings

Identification of low-energy vibrational modes in amorphous Al$_{2}$O$_{3}$

Detection of electronic states that may contribute to TLSs

Insights into the microscopic origin of decoherence in superconducting qubits

Abstract

Amorphous Al$_{2}$O$_{3}$ is a fundamental component of modern superconducting qubits. While amphorphous oxides offer distinct advantages, such as directional isotropy and a consistent bulk electronic gap, in realistic systems these compounds support two-level systems (TLSs) which couple to the qubit, expediting decoherence. In this work, we perform a first-principles study of amorphous Al$_{2}$O$_{3}$ and identify low-energy modes in the electronic and phonon spectra as a possible origin for TLSs.