Random two-level defects in polycrystalline and amorphous alumina

Atomic two-level system (TLSs) are ubiquitous defects in superconducting qubits, however the TLS host material is generally amorphous alumina. We extend a characterization technique to, for the first time, study TLSs in two states of the same material: amorphous and polycrystalline alumina. A large distribution of approximately 400 individual TLS dipole moments are obtained in polycrystalline AlOx along a common axis. The averaged dipole moment in material is approximately 3.1 Debye. On the other hand, the average dipole moment is much larger in amorphous alumina, which is contradicted by expectations. We observe strong TLS frequency drifting phenomenon in the amorphous sample which relates to its TLS-TLS interactions. For the first time, a material characterization technique shows that one can collect a large amount of individual TLS data for material optimization, such as TLS dipole moments and TLS frequency stability.