Li Li

Stable and Efficient Charging of Superconducting C-shunt Flux Quantum Batteries

  1. Li Li,
  2. Si-Lu Zhao,
  3. Yun-Hao Shi,
  4. Bing-Jie Chen,
  5. Xinhui Ruan,
  6. Gui-Han Liang,
  7. Wei-Ping Yuan,
  8. Jia-Cheng Song,
  9. Cheng-Lin Deng,
  10. Yu Liu,
  11. Tian-Ming Li,
  12. Zheng-He Liu,
  13. Xue-Yi Guo,
  14. Xiaohui Song,
  15. Kai Xu,
  16. Heng Fan,
  17. Zhongcheng Xiang,
  18. and Dongning Zheng
Quantum batteries, as miniature energy storage devices, have sparked significant research interest in recent years. However, achieving rapid and stable energy transfer in quantum batteries
while obeying quantum speed limits remains a critical challenge. In this work, we experimentally optimize the charging process by leveraging the unique energy level structure of a superconducting capacitively-shunted flux qubit, using counterdiabatic pulses in the stimulated Raman adiabatic passage. Compared to previous studies, we impose two different norm constraints on the driving Hamiltonian, achieving optimal charging without exceeding the overall driving strength. Furthermore, we experimentally demonstrate a charging process that achieves the quantum speed limit. In addition, we introduce a dimensionless parameter  to unify charging speed and stability, offering a universal metric for performance optimization. In contrast to metrics such as charging power and thermodynamic efficiency, the  criterion quantitatively captures the stability of ergentropy while also considering the charging speed. Our results highlight the potential of the capacitively-shunted qubit platform as an ideal candidate for realizing three-level quantum batteries and deliver novel strategies for optimizing energy transfer protocols.
arxiv pdf

Tunable coupling of a quantum phononic resonator to a transmon qubit with flip-chip architecture

  1. Xinhui Ruan,
  2. Li Li,
  3. Guihan Liang,
  4. Silu Zhao,
  5. Jia-heng Wang,
  6. Yizhou Bu,
  7. Bingjie Chen,
  8. Xiaohui Song,
  9. Xiang Li,
  10. He Zhang,
  11. Jinzhe Wang,
  12. Qianchuan Zhao,
  13. Kai Xu,
  14. Heng Fan,
  15. Yu-xi Liu,
  16. Jing Zhang,
  17. Zhihui Peng,
  18. Zhongcheng Xiang,
  19. and Dongning Zheng
A hybrid system with tunable coupling between phonons and qubits shows great potential for advancing quantum information processing. In this work, we demonstrate strong and tunable
coupling between a surface acoustic wave (SAW) resonator and a transmon qubit based on galvanic-contact flip-chip technique. The coupling strength varies from 2π×7.0 MHz to -2π×20.6 MHz, which is extracted from different vacuum Rabi oscillation frequencies. The phonon-induced ac Stark shift of the qubit at different coupling strengths is also shown. Our approach offers a good experimental platform for exploring quantum acoustics and hybrid systems.
arxiv pdf