Xiaoyu Xia

Tunable Hybrid-Mode Coupler Enabling Strong Interactions between Transmons at Centimeter-Scale Distance

  1. Jianwen Xu,
  2. Xiang Deng,
  3. Wen Zheng,
  4. Wenchang Yan,
  5. Tao Zhang,
  6. Zhenchuan Zhang,
  7. Wanli Huang,
  8. Xiaoyu Xia,
  9. Xudong Liao,
  10. Yu Zhang,
  11. Jie Zhao,
  12. Shaoxiong Li,
  13. Xinsheng Tan,
  14. Dong Lan,
  15. and Yang Yu
The transmon, a fabrication-friendly superconducting qubit, remains a leading candidate for scalable quantum computing. Recent advances in tunable couplers have accelerated progress
toward high-performance quantum processors. However, extending coherent interactions beyond millimeter scales to enhance quantum connectivity presents a critical challenge. Here, we introduce a hybrid-mode coupler exploiting resonator-transmon hybridization to simultaneously engineer the two lowest-frequency mode, enabling high-contrast coupling between centimeter-scale transmons. For a 1-cm coupler, our framework predicts flux-tunable XX and ZZ coupling strengths reaching 23 MHz and 100 MHz, with modulation contrasts exceeding 102 and 104, respectively, demonstrating quantitative agreement with an effective two-channel model. This work provides an efficient pathway to mitigate the inherent connectivity constraints imposed by short-range interactions, enabling transmon-based architectures compatible with hardware-efficient quantum tasks.
arxiv pdf

Fabrication of airbridges with gradient exposure

  1. Yuting Sun,
  2. Jiayu Ding,
  3. Xiaoyu Xia,
  4. Xiaohan Wang,
  5. Jianwen Xu,
  6. Shuqing Song,
  7. Dong Lan,
  8. Jie Zhao,
  9. and Yang Yu
In superconducting quantum circuits, airbridges are critical for eliminating parasitic slotline modes of coplanar waveguide circuits and reducing crosstalks between direct current magnetic
flux biases. Here, we present a technique for fabricating superconducting airbridges. With this technique, a single layer of photoresist is employed, and the gradient exposure process is used to define the profile of airbridges. In order to properly obtain the bridge profile, we design exposure dosage based on residual photoresist thickness and laser power calibrations. Compared with other airbridge fabrication techniques, the gradient exposure fabrication technique provides the ability to produce lossless superconducting airbridges with flexible size and, thus, is more suitable for large-scale superconducting quantum circuits. Furthermore, this method reduces the complexity of the fabrication process and provides a high fabrication yield.
arxiv pdf