E. P. A. M. Bakkers

Read out the fermion parity of a potential artificial Kitaev chain utilizing a transmon qubit

  1. Enna Zhuo,
  2. Xiaozhou Yang,
  3. Yuyang Huang,
  4. Zhaozheng Lyu,
  5. Ang Li,
  6. Bing Li,
  7. Yunxiao Zhang,
  8. Xiang Wang,
  9. Duolin Wang,
  10. Yukun Shi,
  11. Anqi Wang,
  12. E. P. A. M. Bakkers,
  13. Xiaodong Han,
  14. Xiaohui Song,
  15. Peiling Li,
  16. Bingbing Tong,
  17. Ziwei Dou,
  18. Guangtong Liu,
  19. Fanming Qu,
  20. Jie Shen,
  21. and Li Lu
Artificial Kitaev chains have emerged as a promising platform for realizing topological quantum computing. Once the chains are formed and the Majorana zero modes are braided/fused,
reading out the parity of the chains is essential for further verifying the non-Abelian property of the Majorana zero modes. Here we demonstrate the feasibility of using a superconducting transmon qubit, which incorporates an end of a four-site quantum dot-superconductor chain based on a Ge/Si nanowire, to directly detect the singlet/doublet state, and thus the parity of the entire chain. We also demonstrate that for multiple-dot chains there are two types of 0-{\pi} transitions between different charging states: the parity-flip 0-{\pi} transition and the parity-preserved 0-{\pi} transition. Furthermore, we show that the inter-dot coupling, hence the strengths of cross Andreev reflection and elastic cotunneling of electrons, can be adjusted by local electrostatic gating in chains fabricated on Ge/Si core-shell nanowires. Our exploration would be helpful for the ultimate realization of topological quantum computing based on artificial Kitaev chains.
arxiv pdf

Realization of microwave quantum circuits using hybrid superconducting-semiconducting nanowire Josephson elements

  1. G. de Lange,
  2. B. van Heck,
  3. A. Bruno,
  4. D. J. van Woerkom,
  5. A. Geresdi,
  6. S. R. Plissard,
  7. E. P. A. M. Bakkers,
  8. A. R. Akhmerov,
  9. and L. DiCarlo
We report the realization of quantum microwave circuits using hybrid superconductor-semiconductor Josephson elements comprised of InAs nanowires contacted by NbTiN. Capacitively-shunted
single elements behave as transmon qubits with electrically tunable transition frequencies. Two-element circuits also exhibit transmon-like behavior near zero applied flux, but behave as flux qubits at half the flux quantum, where non-sinusoidal current-phase relations in the elements produce a double-well Josephson potential. These hybrid Josephson elements are promising for applications requiring microwave superconducting circuits operating in magnetic field.
arxiv pdf