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Volume 19 Issue 7, July 2023

Solitons in synthetic dimensions

Synthetic dimensions can introduce band properties without a periodic structure in real space, but they have largely been studied in linear systems. Now, Nicolas Englebert and collaborators present a study using an optical resonator that shows nonlinear soliton states in synthetic frequency space. This will allow the manipulation of dissipative cavity solitons with potential applications in optical frequency comb generation and nonlinear topological photonics.

See Englebert et al.

Image: Loïc Brunot. Cover Design: Amie Fernandez.


  • 75 years ago, Claude E. Shannon’s ‘A mathematical theory of communication’ appeared in Bell Labs’s research journal, marking the birth of the discipline of information theory. This month, we celebrate the influence of Shannon’s work, as well as his eccentric attitude.



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Books & Arts

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News & Views

  • Although quantum spin liquids have long been theoretically studied, an experimental demonstration has remained challenging. An inorganic oxide presents an ideal candidate to realize this disordered state.

    • Jie Ma
    News & Views
  • The combination of magnetic and non-magnetic layers in (MnBi2Te4)(Bi2Te3) is predicted to produce topologically protected states on the surface. Experiments now show that the nature of the topmost layer controls the location of these states.

    • Matthew Brahlek
    • Robert G. Moore
    News & Views
  • The structure of disordered materials typically ages, but sometimes also rejuvenates, resulting in intriguing memory properties. Progress in numerical simulations of spin glasses has now enabled replication of such phenomena from simple models.

    • Eric Vincent
    News & Views
  • Time-varying photonics constitutes an emerging concept where a material’s time-dependence is used to achieve novel functionalities. A temporal double-slit-diffraction experiment demonstrates the feasibility of time-modulating materials to control light.

    • Francisco J. Rodríguez-Fortuño
    News & Views
  • Levitated nanoparticles can now be cooled to the motional ground state in two dimensions. This advance could enable a new generation of macroscopic quantum experiments.

    • Dalziel J. Wilson
    News & Views
  • A quantum engineering technique powered by disorder offers access to local correlation functions down to single-site resolution in nuclear spin ensembles, allowing the study of both spin and energy hydrodynamics.

    • Yaoming Chu
    • Jianming Cai
    News & Views
  • Research in the past few decades has uncovered powerful generalities in the structure of many natural and built networks. Now, a study describes how certain structural properties of networks may cause them to endure or collapse over time.

    • Neo D. Martinez
    • Richard J. Williams
    News & Views
  • Developing tissues undergo collective cell movement and changes to their material properties, such as flow characteristics. Now tissue fluidity is linked to tissue growth.

    • Asako Shindo
    News & Views
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Research Briefings

  • Time crystals are a new state of matter. Conventional crystal properties are periodic in space, while the properties of a time crystal are periodic in time. A continuous quantum time crystal has recently been realized, and now, using optically driven many-body interactions in a nano-mechanical photonic metamaterial, a classical continuous time crystal has been created.

    Research Briefing
  • It’s a long-standing theoretical prediction that mutual information in locally interacting, many-body quantum systems follows an area law. Using cold-atom quantum-field simulators on an atom chip to measure the scaling of von Neumann entropy and mutual information, that prediction is now proved true.

    Research Briefing
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  • Spin liquids are predicted to emerge in materials that combine strong electronic correlations with geometric frustration. Evidence has now been found for a spin liquid state in the triangular-lattice material NaRuO2.

    • Brenden R. Ortiz
    • Paul M. Sarte
    • Stephen D. Wilson
  • Layering quantum materials can produce interesting phenomena by combining the different behaviour of electronic states in each layer. A layer-sensitive measurement technique provides insights into the physics of a magnetic topological insulator.

    • Woojoo Lee
    • Sebastian Fernandez-Mulligan
    • Shuolong Yang
  • Glasses relax internally even when their structure is frozen. Observations of a two-dimensional glass former now show that although structure relaxation freezes with the glass transition, non-constrained bonds survive; this accounts for persisting internal relaxation.

    • Yanshuang Chen
    • Zefang Ye
    • Peng Tan
  • So far, a continuous time crystal has only been implemented on a quantum system. Optically driven many-body interactions in a nanomechanical photonic metamaterial now allow the realization of a classical continuous time crystal.

    • Tongjun Liu
    • Jun-Yu Ou
    • Nikolay I. Zheludev
    Article Open Access
  • Some topological boundary states are symmetry protected. Experiments with photonic lattices now show that the protection via sub-symmetry is enough to ensure topological modes, even if the full symmetry and topological invariant are destroyed.

    • Ziteng Wang
    • Xiangdong Wang
    • Hrvoje Buljan
    Article Open Access
  • A temporal version of Young’s double-slit experiment shows characteristic interference in the frequency domain when light interacts with time slits produced by ultrafast changes in the refractive index of an epsilon-near-zero material.

    • Romain Tirole
    • Stefano Vezzoli
    • Riccardo Sapienza
  • Probing strongly interacting quantum systems with high spatial resolution can be challenging. An experiment now uses disorder in nuclear spin chains as a local probe to investigate spin and energy hydrodynamics.

    • Pai Peng
    • Bingtian Ye
    • Paola Cappellaro
  • Despite looking highly irregular, most real-world networks exhibit natural stability to external perturbations. A study of the properties of the stability matrix of networks now sheds light on the principles underlying this emerging stability.

    • Chandrakala Meena
    • Chittaranjan Hens
    • Baruch Barzel
  • Tests of the predictions of the renormalization group in biological experiments have not yet been decisive. Now, a study on the collective dynamics of insect swarms provides a long-sought match between experiment and theory.

    • Andrea Cavagna
    • Luca Di Carlo
    • Mattia Scandolo
    Article Open Access
  • Elastoviscoplastic fluids combine solid- and liquid-like behaviour depending on applied stress. Simulations of elastoviscoplastic fluids at high Reynolds number now show that plasticity plays a key role in the turbulent flows seen in these systems, leading for example to intermittency.

    • Mohamed S. Abdelgawad
    • Ianto Cannon
    • Marco E. Rosti
    Article Open Access
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Measure for Measure

  • The unit one is a necessary part of any system of units but debate concerning its proper treatment in science and technology continues. Richard Brown enumerates its uses.

    • Richard J. C. Brown
    Measure for Measure
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