近日，美国QuEra Computing公司的Sheng-Tao Wang及其研究团队取得一项新进展。经过不懈努力，他们揭示完全阻塞里德伯原子系综的量子动力学。相关研究成果已于2024年4月16日在国际知名学术期刊《物理评论A》上发表。

该研究团队专注于研究具有排列对称性的强相互作用原子系综，通过这一特性，研究人员成功地在任意长的演化时间内计算出了数百个原子的某些集体观测值。这一系统是通过一个特殊的三能级原子系综来实现的，其中一个能级对应于高度激发的里德伯态。在全对全里德伯阻塞的极限条件下，原子排列的变化并不会影响哈密顿量。

利用表象理论中的技术，研究人员构造了哈密顿量的块对角线形式，其中最大块的大小仅随系统大小线性增加。研究人员应用这一形式推导出有效的脉冲序列。从而制备出任意排列不变的量子态。此外，他们研究了猝灭后的量子动力学，揭示了系统缓慢热化并表现出明显复苏的参数状态。这项研究结果为大型相互作用和不可积量子系统的实验和理论研究创造了机会。

据悉，经典模拟在量子系统研究中扮演着举足轻重的角色，尤其在研究多体现象以及量子技术基准测试和验证方面。然而，由于希尔伯特空间的维度会随着系统规模的扩大而呈指数级增长，因此精确的模拟通常仅限于小型系统。不过，值得庆幸的是，对于具备高度对称性的系统，经典模拟可以触及更大尺寸的范围。

附：英文原文

Title: Quantum dynamics of a fully blockaded Rydberg atom ensemble

Author: Dominik S. Wild, Sabina Drgoi, Corbin McElhanney, Jonathan Wurtz, Sheng-Tao Wang

Issue&Volume: 2024/04/16

Abstract: Classical simulation of quantum systems plays an important role in the study of many-body phenomena and in the benchmarking and verification of quantum technologies. Exact simulation is often limited to small systems because the dimension of the Hilbert space increases exponentially with the size of the system. For systems that possess a high degree of symmetry, however, classical simulation can reach much larger sizes. Here we consider an ensemble of strongly interacting atoms with permutation symmetry, enabling the computation of certain collective observables for hundreds of atoms at arbitrarily long evolution times. The system is realized by an ensemble of three-level atoms, where one of the levels corresponds to a highly excited Rydberg state. In the limit of all-to-all Rydberg blockade, the Hamiltonian is invariant under permutation of the atoms. Using techniques from representation theory, we construct a block-diagonal form of the Hamiltonian, where the size of the largest block increases only linearly with the system size. We apply this formalism to derive efficient pulse sequences to prepare arbitrary permutation-invariant quantum states. Moreover, we study the quantum dynamics following a quench, uncovering a parameter regime in which the system thermalizes slowly and exhibits pronounced revivals. Our results create opportunities for the experimental and theoretical study of large interacting and nonintegrable quantum systems.

DOI: 10.1103/PhysRevA.109.043111

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.109.043111