中国物理B ›› 2025, Vol. 34 ›› Issue (11): 110302-110302.doi: 10.1088/1674-1056/ae00b0

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Efficient characterization of the coupler spectrum via sideband driving in superconducting qubits

Jianwen Xu(徐建文)1,2,3,†, Ruonan Guo(郭若男)1,2,3,†, Wen Zheng(郑文)1,2,3,‡, Yu Zhang(张钰)1,2,3, Jie Zhao(赵杰)1,2,3, Zhiguo Huang(黄智国)4, Jingwei Wen(闻经纬)4, Runqing Zhang(张润清)4, Shaoxiong Li(李邵雄)1,2,3,5,6, Xinsheng Tan(谭新生)1,2,3,5,6, and Yang Yu(于扬)1,2,3,5,6,§   

  1. 1 National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China;
    2 Shishan Laboratory, Nanjing University, Suzhou 215163, China;
    3 Jiangsu Key Laboratory of Quantum Information Science and Technology, Nanjing University, Suzhou 215163, China;
    4 China Mobile (Suzhou) Software Technology Company Limited, Suzhou 215163, China;
    5 Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China;
    6 Hefei National Laboratory, Hefei 230088, China
  • 收稿日期:2025-07-02 修回日期:2025-08-15 接受日期:2025-08-29 发布日期:2025-10-30
  • 基金资助:
    This work was partially supported by the Innovation Program for Quantum Science and Technology (Grant Nos. 2021ZD0301702 and 2024ZD0302000), the Natural Science Foundation of of Jiangsu Province (Grant No. BK20232002), the National Natural Science Foundation of China (Grant Nos. U21A20436 and 12074179), the Natural Science Foundation of Shandong Province (Grant No. ZR2023LZH002), and Nanjing University–China Mobile Communications Group Co., Ltd. Joint Institute.

Efficient characterization of the coupler spectrum via sideband driving in superconducting qubits

Jianwen Xu(徐建文)1,2,3,†, Ruonan Guo(郭若男)1,2,3,†, Wen Zheng(郑文)1,2,3,‡, Yu Zhang(张钰)1,2,3, Jie Zhao(赵杰)1,2,3, Zhiguo Huang(黄智国)4, Jingwei Wen(闻经纬)4, Runqing Zhang(张润清)4, Shaoxiong Li(李邵雄)1,2,3,5,6, Xinsheng Tan(谭新生)1,2,3,5,6, and Yang Yu(于扬)1,2,3,5,6,§   

  1. 1 National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 210093, China;
    2 Shishan Laboratory, Nanjing University, Suzhou 215163, China;
    3 Jiangsu Key Laboratory of Quantum Information Science and Technology, Nanjing University, Suzhou 215163, China;
    4 China Mobile (Suzhou) Software Technology Company Limited, Suzhou 215163, China;
    5 Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China;
    6 Hefei National Laboratory, Hefei 230088, China
  • Received:2025-07-02 Revised:2025-08-15 Accepted:2025-08-29 Published:2025-10-30
  • Contact: Wen Zheng, Yang Yu E-mail:zhengwen@nju.edu.cn;yuyang@nju.edu.cn
  • Supported by:
    This work was partially supported by the Innovation Program for Quantum Science and Technology (Grant Nos. 2021ZD0301702 and 2024ZD0302000), the Natural Science Foundation of of Jiangsu Province (Grant No. BK20232002), the National Natural Science Foundation of China (Grant Nos. U21A20436 and 12074179), the Natural Science Foundation of Shandong Province (Grant No. ZR2023LZH002), and Nanjing University–China Mobile Communications Group Co., Ltd. Joint Institute.

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摘要： Fabrication-friendly superconducting qubits continue to be a leading candidate for scalable quantum computing. Recent developments in tunable couplers have significantly advanced the progress toward practical quantum processors. However, high-performance quantum control, particularly two-qubit gates, depends on the delicate tuning of the coupler spectrum, as misalignment can lead to undesirable phenomena such as frequency crowding, which may cause errors including state leakage. Here, we propose an efficient method for characterizing the coupler spectrum through sideband drivings, obviating the need for additional components in current quantum processors. We demonstrate this technique experimentally by employing both continuous-wave and pulsed measurement protocols, successfully extracting the coupler spectrum. Furthermore, by utilizing the measured coupler spectrum, we calibrate the frequency dependence of the effective coupling strength between two qubits linked by the coupler. The proposed approach offers significant practical benefits, enabling the efficient characterization of the coupler spectrum in existing quantum architectures, thus paving the way for enhanced quantum control and scalability.

关键词: superconducting quantum circuits, tunable coupler, sideband driving

Abstract: Fabrication-friendly superconducting qubits continue to be a leading candidate for scalable quantum computing. Recent developments in tunable couplers have significantly advanced the progress toward practical quantum processors. However, high-performance quantum control, particularly two-qubit gates, depends on the delicate tuning of the coupler spectrum, as misalignment can lead to undesirable phenomena such as frequency crowding, which may cause errors including state leakage. Here, we propose an efficient method for characterizing the coupler spectrum through sideband drivings, obviating the need for additional components in current quantum processors. We demonstrate this technique experimentally by employing both continuous-wave and pulsed measurement protocols, successfully extracting the coupler spectrum. Furthermore, by utilizing the measured coupler spectrum, we calibrate the frequency dependence of the effective coupling strength between two qubits linked by the coupler. The proposed approach offers significant practical benefits, enabling the efficient characterization of the coupler spectrum in existing quantum architectures, thus paving the way for enhanced quantum control and scalability.

Key words: superconducting quantum circuits, tunable coupler, sideband driving

中图分类号:  (Quantum computation architectures and implementations)

  • 03.67.Lx
85.25.Dq (Superconducting quantum interference devices (SQUIDs))