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.
@article{arxiv.1912.05150,
title = {Probing the dynamical phase transition with a superconducting quantum simulator},
author = {Kai Xu and Zheng-Hang Sun and Wuxin Liu and Yu-Ran Zhang and Hekang Li and Hang Dong and Wenhui Ren and Pengfei Zhang and Franco Nori and Dongning Zheng and Heng Fan and H. Wang},
journal= {arXiv preprint arXiv:1912.05150},
year = {2020}
}