Transmon Qubit Chip on Single-Crystal Tantalum (110) film

Ping-Lien Lee^1,2*, Chih-Yao Shih^1,2, Hsiang-Huan Lee¹, Jaw-Shen Tsai^3,4,5, Sheng-Shiuan Yeh^6,7, Wen-Hao Chang^1,2

¹Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
²Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
³RIKEN Center for Quantum Computing (RQC), Wako-shi, Saitama, Japan
⁴Research Institute for Science and Technology, Tokyo University of Science, Tokyo, Japan
⁵Graduate School of Science, Tokyo University of Science, Tokyo, Japan
⁶International College of Semiconductor Technology, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
⁷Center for Emergent Functional Matter Science, National Yang Ming Chiao Tung University, Hsinchu, Taiwan

* Presenter:Ping-Lien Lee, email:zzz7921z@gmail.com

In this study, we compare the performance of Transmon qubits and coplanar waveguide (CPW) resonators based on single-crystalline Tantalum (Ta) (110) film with poly-crystalline Ta(110) films. The fabrication process is optimized for devices based on Ta films on sapphire substrate to minimize loss. The qubit chips and the resonator chips were characterized in a dilution fridge at 10 mK. With time domain pulse microwave experiences, qubit relaxation time (T1) and coherence time (T2) were obtained. The internal quality factor (Qi) extracted from transmission (S21) across the feedline of notch-type resonators based on Ta films by using a vector network analyzer (VNA). The quality factor indicated that resonators fabricated on single-crystalline Ta(110) films exhibited a reduced two-level system (TLS) loss compared to those on polycrystalline Ta films at low-photon region. Moreover, the Transmon qubits fabricated on single-crystalline Ta films show a longer T1 relative to those on polycrystalline Ta films by 52%. The result highlights the role of superconducting film crystalline quality in application of quantum devices. This research provides a promising path toward advancing qubit relaxation time by material optimization.

Keywords: Superconducting qubit, Transmon, Qubit, Tantalum