Silu Zhao

Demonstration of High-Fidelity Gates in a Strongly Anharmonic with Long-Coherence C-Shunt Flux Qubit

  1. Silu Zhao,
  2. Li Li,
  3. Weiping Yuan,
  4. Xinhui Ruan,
  5. Jinzhe Wang,
  6. Bingjie Chen,
  7. Yunhao Shi,
  8. Guihan Liang,
  9. Shi Xiao,
  10. Jiacheng Song,
  11. Jinming Guo,
  12. Xiaohui Song,
  13. Kai Xu,
  14. Heng Fan,
  15. Zhongcheng Xiang,
  16. and Dongning Zheng
We demonstrate high-fidelity single-qubit gates on a C-shunt flux qubit that simultaneously combines a large anharmonicity (/2π=848 MHz) with long relaxation time (T1=23 μs). The
large anharmonicity significantly suppresses leakage to higher energy levels, enabling fast and precise microwave control. Using DRAG pulses and randomized benchmarking, the qubit achieves gate fidelities exceeding 99.9\%, highlighting the capability of C-shunt flux qubits for robust and high-performance quantum operations. These results establish them as a promising platform for scalable quantum information processing.
arxiv pdf

Experimental Extraction of Coherent Ergotropy and Its Energetic Cost in a Superconducting Qubit

  1. Li Li,
  2. Silu Zhao,
  3. Kai Xu,
  4. Heng Fan,
  5. Dongning Zheng,
  6. and Zhongcheng Xiang
Quantum coherence, encoded in the off-diagonal elements of a system’s density matrix, is a key resource in quantum thermodynamics, fundamentally limiting the maximum extractable
work, or ergotropy. While previous experiments have isolated coherence-related contributions to work extraction, it remains unclear how coherence can be harnessed in a controllable and energy-efficient manner. Here, we experimentally investigate the role of initial-state coherence in work extraction from a superconducting transmon qubit. By preparing a range of pure states and implementing three complementary extraction protocols, we reveal how coherence governs the partitioning of ergotropy. We find that the choice of initial state depends on the dominant decoherence channel-energy relaxation or dephasing. By further accounting for thermodynamic costs, we identify optimal initial states that maximize the efficiency. These results establish initial-state design as a practical and scalable approach to coherence control, offering guidance for the development of efficient quantum thermodynamic devices.
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