Yichun Gao

Selective-Area-Grown PbTe-Pb Planar Josephson Junctions for Quantum Devices

  1. Ruidong Li,
  2. Wenyu Song,
  3. Wentao Miao,
  4. Zehao Yu,
  5. Zhaoyu Wang,
  6. Shuai Yang,
  7. Yichun Gao,
  8. Yuhao Wang,
  9. Fangting Chen,
  10. Zuhan Geng,
  11. Lining Yang,
  12. Jiaye Xu,
  13. Xiao Feng,
  14. Tiantian Wang,
  15. Yunyi Zang,
  16. Lin Li,
  17. Runan Shang,
  18. Qi-Kun Xue,
  19. Ke He,
  20. and Hao Zhang
Planar Josephson junctions are predicted to host Majorana zero modes. The material platforms in previous studies are two dimensional electron gases (InAs, InSb, InAsSb and HgTe) coupled
to a superconductor such as Al or Nb. Here, we introduce a new material platform for planar JJs, the PbTe-Pb hybrid. The semiconductor, PbTe, was grown as a thin film via selective area epitaxy. The Josephson junction was defined by a shadow wall during the deposition of the superconductor Pb. Scanning transmission electron microscopy reveals a sharp semiconductor-superconductor interface. Gate-tunable supercurrent and multiple Andreev reflections are observed. A perpendicular magnetic field causes interference patterns of the switching current, exhibiting Fraunhofer-like and SQUID-like behaviors. We further demonstrate a prototype device for Majorana detection, wherein phase bias and tunneling spectroscopy are applicable.
arxiv pdf

Gatemon qubit based on a thin InAs-Al hybrid nanowire

  1. Jierong Huo,
  2. Zezhou Xia,
  3. Zonglin Li,
  4. Shan Zhang,
  5. Yuqing Wang,
  6. Dong Pan,
  7. Qichun Liu,
  8. Yulong Liu,
  9. Zhichuan Wang,
  10. Yichun Gao,
  11. Jianhua Zhao,
  12. Tiefu Li,
  13. Jianghua Ying,
  14. Runan Shang,
  15. and Hao Zhang
We study a gate-tunable superconducting qubit (gatemon) based on a thin InAs-Al hybrid nanowire. Using a gate voltage to control its Josephson energy, the gatemon can reach the strong
coupling regime to a microwave cavity. In the dispersive regime, we extract the energy relaxation time T1∼0.56 μs and the dephasing time T∗2∼0.38 μs. Since thin InAs-Al nanowires can have fewer or single sub-band occupation and recent transport experiment shows the existence of nearly quantized zero-bias conductance peaks, our result holds relevancy for detecting Majorana zero modes in thin InAs-Al nanowires using circuit quantum electrodynamics.
arxiv pdf