Chao Song

Emulating many-body localization with a superconducting quantum processor

  1. Kai Xu,
  2. Jin-Jun Chen,
  3. Yu Zeng,
  4. Yuran Zhang,
  5. Chao Song,
  6. Wuxin Liu,
  7. Qiujiang Guo,
  8. Pengfei Zhang,
  9. Da Xu,
  10. Hui Deng,
  11. Keqiang Huang,
  12. H. Wang,
  13. Xiaobo Zhu,
  14. Dongning Zheng,
  15. and Heng Fan
The law of statistical physics dictates that generic closed quantum many-body systems initialized in nonequilibrium will thermalize under their own dynamics. However, the emergence
of many-body localization (MBL) owing to the interplay between interaction and disorder, which is in stark contrast to Anderson localization that only addresses noninteracting particles in the presence of disorder, greatly challenges this concept because it prevents the systems from evolving to the ergodic thermalized state. One critical evidence of MBL is the long-time logarithmic growth of entanglement entropy, and a direct observation of it is still elusive due to the experimental challenges in multiqubit single-shot measurement and quantum state tomography. Here we present an experiment of fully emulating the MBL dynamics with a 10-qubit superconducting quantum processor, which represents a spin-1/2 XY model featuring programmable disorder and long-range spin-spin interactions. We provide essential signatures of MBL, such as the imbalance due to the initial nonequilibrium, the violation of eigenstate thermalization hypothesis, and, more importantly, the direct evidence of the long-time logarithmic growth of entanglement entropy. Our results lay solid foundations for precisely simulating the intriguing physics of quantum many-body systems on the platform of large-scale multiqubit superconducting quantum processors.
arxiv pdf

10-qubit entanglement and parallel logic operations with a superconducting circuit

  1. Chao Song,
  2. Kai Xu,
  3. Wuxin Liu,
  4. Chuiping Yang,
  5. Shi-Biao Zheng,
  6. Hui Deng,
  7. Qiwei Xie,
  8. Keqiang Huang,
  9. Qiujiang Guo,
  10. Libo Zhang,
  11. Pengfei Zhang,
  12. Da Xu,
  13. Dongning Zheng,
  14. Xiaobo Zhu,
  15. H. Wang,
  16. Y.-A. Chen,
  17. C.-Y. Lu,
  18. Siyuan Han,
  19. and J.-W. Pan
Here we report on the production and tomography of genuinely entangled Greenberger-Horne-Zeilinger states with up to 10 qubits connecting to a bus resonator in a superconducting circuit,
where the resonator-mediated qubit-qubit interactions are used to controllably entangle multiple qubits and to operate on different pairs of qubits in parallel. The resulting 10-qubit density matrix is unambiguously probed, with a fidelity of 0.668±0.025. Our results demonstrate the largest entanglement created so far in solid-state architectures, and pave the way to large-scale quantum computation.
arxiv pdf

Solving Systems of Linear Equations with a Superconducting Quantum Processor

  1. Yarui Zheng,
  2. Chao Song,
  3. Ming-Cheng Chen,
  4. Benxiang Xia,
  5. Wuxin Liu,
  6. Qiujiang Guo,
  7. Libo Zhang,
  8. Da Xu,
  9. Hui Deng,
  10. Keqiang Huang,
  11. Yulin Wu,
  12. Zhiguang Yan,
  13. Dongning Zheng,
  14. Li Lu,
  15. Jian-Wei Pan,
  16. H. Wang,
  17. Chao-Yang Lu,
  18. and Xiaobo Zhu
Superconducting quantum circuits are promising candidate for building scalable quantum computers. Here, we use a four-qubit superconducting quantum processor to solve a two-dimensional
system of linear equations based on a quantum algorithm proposed by Harrow, Hassidim, and Lloyd [Phys. Rev. Lett. \textbf{103}, 150502 (2009)], which promises an exponential speedup over classical algorithms under certain circumstances. We benchmark the solver with quantum inputs and outputs, and characterize it by non-trace-preserving quantum process tomography, which yields a process fidelity of 0.837±0.006. Our results highlight the potential of superconducting quantum circuits for applications in solving large-scale linear systems, a ubiquitous task in science and engineering.
arxiv pdf