Fabrication of Superconducting Qubits via a Low Damaging Window Junction Process

Jun-Yi Tsai^1*, Chung-Ting Ke^1,2, Yen-Chun Chen¹, Zhen-Wei, Xu¹, Elam Blackwell³, Matthew A. Snyder³, Spencer Weeden³, Peng-Sheng Chen⁴, Chih-Ming Lai⁴, Shyh-Shyuan Sheu⁴, Zihao Yang⁵, Cen-Shawn Wu^6,1, Alan Ho⁷, Robert McDermott^3,7, John Martinis^7,8, Chii-Dong Chen^2,1

¹Research Center for Critical Issues, Academia Sinica, Tainan, Taiwan
²Institute of Physics, Academia Sinica, Taipei, Taiwan
³Department of Physics, University of Wisconsin-Madison, Wisconsin, USA
⁴Electronic and Optoelectronic System Research Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan
⁵Applied Materials, Santa Clara, California, USA
⁶Department of Physics, National Changhua University of Education, Changhua, Taiwan
⁷Qolab, Wisconsin, USA
⁸Department of Physics, University of California Santa Barbara, California, USA

* Presenter:Jun-Yi Tsai, email:jytsai@gate.sinica.edu.tw

Josephson junctions are fundamental building blocks for superconducting circuits to realize quantum technologies, including scaling the number and improving the quality of superconducting qubits for fault tolerant quantum computing. Comparing to the conventional tilted angle deposition associated with lift-off fabrication process, CMOS-compatible methods like overlap and trilayer junctions are promising alternatives. In this talk, we introduce the window junction architecture, avoiding steps that cause the structural damage by a silicon oxide scaffold layer during most of the fabrication process. Our initial research demonstrates a single qubit with a relaxation time reaching up to 57 μs [1]. Further analysis indicates the relaxation time can be improved by optimizing the measurement protocols and device design. This work paves a way for the CMOS-compatible fabrication process and potentially to minimize damage to the substrate and material surfaces.

[1]: arXiv:2503.11010 (2025) Scaffold-Assisted Window Junctions for Superconducting Qubit Fabrication

Keywords: superconducting qubit, quantum computing, Josephson junction