Direct observation of a dynamical glass transition in a nanomagnetic artificial Hopfield network
Michael Saccone, Francesco Caravelli, Kevin Hofhuis, Sergii Parchenko, Yorick A. Birkhölzer, Scott Dhuey, Armin Kleibert, Sebastiaan van Dijken, Cristiano Nisoli, Alan Farhan
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Initial submission to Nature Physics. 20 pages, 4 figures
Spin glasses, generally defined as disordered systems with randomized competing interactions, are a widely investigated complex system. Theoretical models describing spin glasses are broadly used in other complex systems, such as those describing brain function, error-correcting codes, or stock-market dynamics. This wide interest in spin glasses provides strong motivation to generate an artificial spin glass within the framework of artificial spin ice systems. Here, we present the experimental realization of an artificial spin glass consisting of dipolar coupled single-domain Ising-type nanomagnets arranged onto an interaction network that replicates the aspects of a Hopfield neural network. Using cryogenic x-ray photoemission electron microscopy (XPEEM), we performed temperature-dependent imaging of thermally driven moment fluctuations within these networks and observed characteristic features of a two-dimensional Ising spin glass. Specifically, the temperature dependence of the spin glass correlation function follows a power law trend predicted from theoretical models on two-dimensional spin glasses. Furthermore, we observe clear signatures of the hard to observe rugged spin glass free energy in the form of sub-aging, out of equilibrium autocorrelations and a transition from stable to unstable dynamics.
The infinite volume limit of the Hopfield neural networks in the replica-symmetric regime
Sapienza Università di Roma（罗马第一大学）；Istituto Nazionale di Fisica Nucleare, Sezione di Roma（意大利国家核物理研究所罗马分部）；CNR Nanotec, Salento Unit（意大利国家研究委员会纳米技术研究所莱切单元）；Università del Salento（萨伦托大学）；Istituto Nazionale di Fisica Nucleare, Sezione di Lecce（意大利国家核物理研究所莱切分部）
Learning About Learning: A Path from Spin Glasses to Artificial Intelligence
NeuroPhysics Laboratory, Departamento de Física, Universidade Federal de Santa Catarina, Florianópolis SC, Brazil. 88040-900（神经物理实验室，物理系，圣卡塔琳娜联邦大学，弗洛里亚诺波利斯SC，巴西。88040-900）
Supercooling and fragile glassiness in a dipolar kagome Ising magnet
我们研究了经典偶极kagome伊辛反铁磁体中的平衡和有序，我们发现它表现为无无序的易碎自旋玻璃。通过确定适当的序参量，我们证明了向Chioar等人提出的有序态的转变。[Phys. Rev. B 93，214410（2016）]具有打破时间反演和亚晶格对称性的12位晶胞，并进一步提供证据表明转变的性质是一阶的。在接近转变时，自旋动力学急剧减慢。该系统很容易失去平衡，过冲过渡和进入一个过冷液体制度。利用广泛的蒙特卡罗模拟，我们表明，该系统具有超Arrhenius行为以上的顺序过渡。弛豫时间发散根据Vogel-Fulcher形式在一个有限的“玻璃化转变”温度在过冷制度。这样的行为，脆弱的玻璃的特性，是特别显着的，因为该模型是免费的淬火无序，不直接符合避免的临界范式，是简单的和突出的工程纳米磁性阵列中实现。
Observation of associative-memory retrieval and spin-glass phases on a photonic quantum simulator
Sapienza Università di Roma（罗马大学）；Università del Salento（萨伦托大学）；Institute of Nanotechnology of the National Research Council of Italy, CNR-NANOTEC（意大利国家研究委员会纳米技术研究所）；Università degli Studi di Salerno（萨莱诺大学）；INFN, Sezione di Napoli, Gruppo Collegato di Salerno（意大利国家核物理研究所那不勒斯分部萨莱诺协作组）；Department of Computing Sciences, Bocconi University（博科尼大学计算科学系）；Istituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle Ricerche (IFN-CNR)（意大利国家研究委员会光子和纳米技术研究所）
Quantum effects in rotationally invariant spin glass models
The University of Tokyo（东京大学）；Institute for Physics of Intelligence, The University of Tokyo（东京大学物理智能研究所）；Trans-Scale Quantum Science Institute, The University of Tokyo（东京大学跨尺度量子科学研究所）
Department of Computer Science, Australian Artificial Intelligence Institute, Faculty of Engineering and Information Technology, University of Technology Sydney（计算机科学系、澳大利亚人工智能研究所、工程与信息技术学院、新南威尔士大学）
Istituto Nazionale d’Alta Matematica, GNFM（高等数学国立研究所，GNFM）；Istituto Nazionale di Fisica Nucleare, Sezione di Lecce（国家核物理研究所，莱切分部）；Istituto Nazionale di Fisica Nucleare, Sezione di Roma1（国家核物理研究所，罗马第一分部）；CNR-Nanotec, Rome unit（国家研究委员会纳米技术研究所，罗马分部）
