Probing the dynamical phase transition with a superconducting quantum simulator

  1. Kai Xu,
  2. Zheng-Hang Sun,
  3. Wuxin Liu,
  4. Yu-Ran Zhang,
  5. Hekang Li,
  6. Hang Dong,
  7. Wenhui Ren,
  8. Pengfei Zhang,
  9. Franco Nori,
  10. Dongning Zheng,
  11. Heng Fan,
  12. and H. Wang
Non-equilibrium quantum many-body systems, which are difficult to study via classical computation, have attracted wide interest. Quantum simulation can provide insights into these problems. Here, using a programmable quantum simulator with 16 all-to-all connected superconducting qubits, we investigate the dynamical phase transition in the Lipkin-Meshkov-Glick model with a quenched transverse field. Clear signatures of the dynamical phase transition, merging different concepts of dynamical criticality, are observed by measuring the non-equilibrium order parameter, nonlocal correlations, and the Loschmidt echo. Moreover, near the dynamical critical point, we obtain the optimal spin squeezing of −7.0±0.8 decibels, showing multipartite entanglement useful for measurements with precision five-fold beyond the standard quantum limit. Based on the capability of entangling qubits simultaneously and the accurate single-shot readout of multi-qubit states, this superconducting quantum simulator can be used to study other problems in non-equilibrium quantum many-body systems.
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