Time reversal in a macroscopic system is contradicting daily experience. It is practically impossible to restore a shattered cup to its original state by just time reversing the microscopic dynamics that led to its breakage. Yet, with the precise control capabilities provided by modern quantum technology, the unitary evolution of a quantum system can be reversed in time. Here, we implement a time-reversal protocol in a dipolar interacting, isolated many-body spin system represented by Rydberg states in an atomic gas. By changing the states encoding the spin, we flip the sign of the interaction Hamiltonian, and demonstrate the reversal of the relaxation dynamics of the magnetization by letting a demagnetized many-body state evolve back-in-time into a magnetized state. We elucidate the role of atomic motion using the concept of a Loschmidt echo. Finally, by combining the approach with Floquet engineering, we demonstrate time reversal for a large family of spin models with different symmetries. Our method of state transfer is applicable across a wide range of quantum simulation platforms and has applications far beyond quantum many-body physics, reaching from quantum-enhanced sensing to quantum information scrambling.
Experimental observation of a phase transition in the evolution of many-body systems with dipolar interactions
多体系统的非平衡动力学在许多科学分支中都很重要，如凝聚态、量子化学和超冷原子。本文报道了具有偶极相互作用的三维多自旋系统的量子相干动力学的相变的实验观测，并确定了它的临界指数。利用室温下的固态自旋系统的核磁共振（NMR），我们淬灭相互作用哈密顿量来驱动系统的演化。由此产生的系统相干性的动态可以是本地化的或扩展的，这取决于淬火强度。应用有限时间标度分析所观察到的相关自旋的数量的时间演化，我们提取的临界指数v = s = 0.42周围的相变分离本地从离域动力学制度。这些结果清楚地表明，这种基于核自旋的量子模拟可以有效地模拟复杂多体系统的非平衡动力学，例如具有偶极相互作用的3D自旋网络。
Strongly dipolar molecular Bose-Einstein condensates: From few- to many-body physics
Vienna Center for Quantum Science and Technology, Atominstitut, TU Wien（维也纳量子科学与技术中心，原子研究所，维也纳工业大学）；MIT-Harvard Center for Ultracold Atoms, Research Laboratory of Electronics, and Department of Physics, Massachusetts Institute of Technology（麻省理工学院-哈佛大学超冷原子中心，电子研究实验室，物理学系，麻省理工学院）；Physikalisches Institut and Center for Integrated Quantum Science and Technology, Universität Stuttgart（第五物理研究所，集成量子科学与技术中心，斯图加特大学）；Department of Physics, Columbia University（物理学系，哥伦比亚大学）；Institute for Theoretical Physics, TU Wien（理论物理研究所，维也纳工业大学）；Department of Physics, The Chinese University of Hong Kong（物理学系，香港中文大学）；Institute for Molecules and Materials, Radboud University（分子与材料研究所，拉德堡德大学）；Université Paris-Saclay, CNRS, Laboratoire Aimé Cotton（巴黎萨克雷大学，法国国家科学研究中心，阿梅·科唐实验室）
Many-body gravitating quantum systems with Bose-Einstein condensates and dipolar analogue
Istituto Nazionale di Ottica, Consiglio Nazionale delle Ricerche (INO-CNR)（意大利国家光学研究所，意大利国家研究委员会）；Physics Department, University of Naples Federico II（那不勒斯费德里科二世大学物理系）；European Laboratory for Nonlinear Spectroscopy (LENS)（欧洲非线性光谱学实验室）；Physics Department, University of Florence（佛罗伦萨大学物理系）
Ultracold Dipolar Gas of Fermionic $^{23}$Na$^{40}$K Molecules in their Absolute Ground State
我们报告创建一个超冷偶极气体的费米子$^{23}$ Na $^{40}$ K分子在其绝对振转和超精细基态。从弱结合Feshbach分子，我们证明了超精细分辨双光子转移到单重态${\rm X}^1Σ^+ |v{=}0,J{=}0\rangle$基态，相干桥接的结合能差为0.65 eV通过受激快速绝热通道。自旋极化，近量子简并分子气体显示寿命超过2.5秒，突出了NaK对两体化学反应的稳定性。施加均匀电场以诱导高达0.8德拜的偶极矩。随着这些进展，对$^{23}$ Na $^{40}$ K分子的强偶极费米气体的多体物理探索已进入实验阶段。
Negative Interaction Quench Dynamics of Density-Ordered Dipolar Bosons in a One-Dimensional Optical Lattice
University of Haifa（海法大学）；The Maharaja Sayajirao University of Baroda（巴罗达马哈拉贾·萨亚吉拉奥大学）；Universidade Federal de Pernambuco（伯南布哥联邦大学）；Universidade de São Paulo（圣保罗大学）
Observing weakly broken conservation laws in a dipolar Rydberg quantum spin chain
Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所）；Université Paris-Saclay, Institut d’Optique Graduate School, CNRS, Laboratoire Charles Fabry（巴黎萨克雷大学、光学研究生院、法国国家科学研究中心、夏尔·法布里实验室）；Université Paris-Saclay, CNRS, Laboratoire de Physique Théorique et Modèles Statistiques（巴黎萨克雷大学、法国国家科学研究中心、理论与统计物理实验室）
