He Zhang

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

Observation of critical phase transition in a generalized Aubry-André-Harper model on a superconducting quantum processor with tunable couplers

  1. Hao Li,
  2. Yong-Yi Wang,
  3. Yun-Hao Shi,
  4. Kaixuan Huang,
  5. Xiaohui Song,
  6. Gui-Han Liang,
  7. Zheng-Yang Mei,
  8. Bozhen Zhou,
  9. He Zhang,
  10. Jia-Chi Zhang,
  11. Shu Chen,
  12. Shiping Zhao,
  13. Ye Tian,
  14. Zhan-Ying Yang,
  15. Zhongcheng Xiang,
  16. Kai Xu,
  17. Dongning Zheng,
  18. and Heng Fan
Quantum simulation enables study of many-body systems in non-equilibrium by mapping to a controllable quantum system, providing a new tool for computational intractable problems. Here,
using a programmable quantum processor with a chain of 10 superconducting qubits interacted through tunable couplers, we simulate the one-dimensional generalized Aubry-André-Harper model for three different phases, i.e., extended, localized and critical phases. The properties of phase transitions and many-body dynamics are studied in the presence of quasi-periodic modulations for both off-diagonal hopping coefficients and on-site potentials of the model controlled respectively by adjusting strength of couplings and qubit frequencies. We observe the spin transport for initial single- and multi-excitation states in different phases, and characterize phase transitions by experimentally measuring dynamics of participation entropies. Our experimental results demonstrate that the newly developed tunable coupling architecture of superconducting processor extends greatly the simulation realms for a wide variety of Hamiltonians, and may trigger further investigations on various quantum and topological phenomena.
arxiv pdf

Probing Operator Spreading via Floquet Engineering in a Superconducting Circuit

  1. S. K. Zhao,
  2. Zi-Yong Ge,
  3. Zhongcheng Xiang,
  4. G. M. Xue,
  5. H. S. Yan,
  6. Z. T. Wang,
  7. Zhan Wang,
  8. H. K. Xu,
  9. F. F. Su,
  10. Z. H. Yang,
  11. He Zhang,
  12. Yu-Ran Zhang,
  13. Xue-Yi Guo,
  14. Kai Xu,
  15. Ye Tian,
  16. H. F. Yu,
  17. D. N. Zheng,
  18. Heng Fan,
  19. and S. P. Zhao
Operator spreading, often characterized by out-of-time-order correlators (OTOCs), is one of the central concepts in quantum many-body physics. However, measuring OTOCs is experimentally
challenging due to the requirement of reversing the time evolution of the system. Here we apply Floquet engineering to investigate operator spreading in a superconducting 10-qubit chain. Floquet engineering provides an effective way to tune the coupling strength between nearby qubits, which is used to demonstrate quantum walks with tunable coupling, dynamic localization, reversed time evolution, and the measurement of OTOCs. A clear light-cone-like operator propagation is observed in the system with multiphoton excitations, and the corresponding spreading velocity is equal to that of quantum walk. Our results indicate that the method has a high potential for simulating a variety of quantum many-body systems and their dynamics, which is also scalable to more qubits and higher dimensional circuits.
arxiv pdf