2022/10/25(Tue)
15:00 -16:00
五樓第一會議室 5F, 1st Meeting Room
視訊演講 Video Seminar [ Meeting Link / ID: 2518 452 2408 / Password: 123456 ]
Title
Deleterious effects of nanoscale two-level defects in superconducting qubits
Speaker
洪智樵博士 (馬里蘭大學) Dr. Chih-Chiao Hung (University of Maryland)Abstract
The nanoscale two-level systems (TLS) create a major decoherence source in quantum information processors. Evidence shows that both relaxation time and decoherence time of superconducting (SC) qubits are limited mostly by the TLS. The choice of novel materials and fabrications have improved the lifetime of SC qubits a few orders of magnitude longer than they were first built. However, for most SC qubits, the quintessential Josephson junction barriers are made of amorphous alumina (AlOx), which hosts a huge amount of inevitable TLSs. The understanding of AlOx TLSs is the key to make progress in quantum computing.
TLSs are not generally understood, either structurally or in atomic composition. Here, I will present the behaviors of TLSs in different structural phases and different material interfaces. We observe bulk polycrystalline oxide has a small average dipole moment and a single-peak histogram suggesting a single TLS origin. On the other hand, bulk amorphous oxide has a wide spread of dipole moment values probably due to the nature of oxygen deficiency content. Moreover, TLSs on the metal-air interface are under stochastic fluctuations unlike those located in the bulk oxides. Our studies provide new information for uncovering an appropriate microscopic model.
Language
演講語言 (Language): in English