Chong Li

Nanoscale electrothermal-switch superconducting diode for electrically programmable superconducting circuits

  1. Tianyu Li,
  2. Jiong Li,
  3. Chong Li,
  4. Peiyuan Huang,
  5. Nuo-Zhou Yang,
  6. Wuyue Xu,
  7. Wen-Cheng Yue,
  8. Yang-Yang Lyu,
  9. Yihuang Xiong,
  10. Xuecou Tu,
  11. Tao Tao,
  12. Xiaoqing Jia,
  13. Qing-Hu Chen,
  14. Huabing Wang,
  15. Peiheng Wu,
  16. and Yong-Lei Wang
Superconducting diodes enable dissipationless directional transport, yet achieving electrical tunability and scalability remains a major challenge for circuit-level integration. Here,
we demonstrate an electrothermal-switch superconducting diode in which a gate-controlled nanoscale hotspot dynamically breaks inversion symmetry in a superconducting nanowire. This mechanism gives rise to two coexisting nonreciprocal transport regimes-one associated with a nonreciprocal superconducting-to-normal transition and the other with ratchet-like vortex dynamics-both originating from the same electrothermal-switch process. The diode exhibits efficiencies up to 42% and 60% for the two regimes, respectively, and can be electrically switched on, off, or reversed in polarity in situ by applying a small gate current. These capabilities enable programmable superconducting circuits that realize electrically reconfigurable full-wave and half-wave rectification. The lithography-compatible design, high performance, and gate-controlled functionality establish a scalable platform for programmable superconducting electronics and hybrid quantum systems.
arxiv pdf

Engineering the microwave to infrared noise photon flux for superconducting quantum systems

  1. Sergey Danilin,
  2. João Barbosa,
  3. Michael Farage,
  4. Zimo Zhao,
  5. Xiaobang Shang,
  6. Jonathan Burnett,
  7. Nick Ridler,
  8. Chong Li,
  9. and Martin Weides
Electromagnetic filtering is essential for the coherent control, operation and readout of superconducting quantum circuits at milliKelvin temperatures. The suppression of spurious modes
around the transition frequencies of a few GHz is well understood and mainly achieved by on-chip and package considerations. Noise photons of higher frequencies — beyond the pair-breaking energies — cause decoherence, and require spectral engineering before reaching the packaged quantum chip. The external wires through the refrigerator down to the quantum circuit provides a direct path, and this article contains quantitative analysis and experimental data for noise photon flux through the coaxial filtered wiring. The coaxial cable attenuation and noise photon flux for typical wiring configurations are provided, and compact cryogenic microwave low-pass filters with CR-110 and Esorb-230 absorptive dielectric fillings along with experimental data at room and cryogenic temperatures and up to 70 GHz presented. The filter cut-off frequencies between 1 to 10 GHz are set by the filter length, and the roll-off is material dependent. The relative dielectric permittivity and magnetic permeability for the Esorb-230 material in the pair-breaking frequency range from 75 to 110 GHz are measured, and the filter properties in this frequency range are calculated. The filter contribution to the noise photon flux implies a dramatic reduction, proving their usefulness for experiments with superconducting quantum systems.
arxiv pdf