Volume 16 Issue 6, 2 June 2020

Automated learning from data by means of deep neural networks is finding use in an ever-increasing number of applications, yet key theoretical questions about how it works remain unanswered. A physics-based approach may help to bridge this gap.

This Perspective argues that an approach called extreme value theory is appropriate for understanding the so-called tail risk of epidemic outbreaks, in particular by demonstrating that the distribution of fatalities due to epidemic outbreaks over the past 2500 years is fat-tailed and dominated by extreme events.

The quark–gluon plasma, in which quarks and gluons are deconfined, is a transient state created in collisions of heavy nuclei. By defining an effective temperature, this temperature and the system’s entropy density and speed of sound are determined.

Isotopes with an odd number of neutrons are usually slightly smaller in size than their even-neutron neighbours. In charge radii of short-lived copper isotopes, a reduction of this effect is observed when the neutron number approaches fifty.

In one-dimensional quantum magnets, complex bound states of magnetic excitations known as Bethe strings have long been predicted. Now, a detailed neutron scattering study of SrCo₂V₂O₈ reveals their magnetic-field-dependent dispersion relation.

Moiré engineering has rapidly gained currency as a means to manipulate electronic states of matter in van der Waals heterostructures. Now, the feat is achieved in epitaxially grown oxide heterostructures, thus opening up fresh opportunities for strongly correlated electronic systems.

What happens to topological materials when their electrons are strongly interacting is an open question. Shao and others demonstrate that ZrSiSe is a material that can address this as it has a topological band structure and non-trivial correlations.

Coupling of the quadrupole moment of an electron in a triple quantum dot to photons has been predicted to be a good platform for reducing the effect of charge noise on the decoherence time of a qubit. Here, the authors create such a coupling.

A passive, heralded and high-fidelity quantum memory network node has been realized, which connects simultaneously to two quantum channels provided by orthogonally aligned optical fibre cavities coupled with a single atom.

Two-dimensional density patterns with two-, four- and six-fold symmetries emerge in homogeneous Bose–Einstein condensates when the atomic interactions are modulated at multiple frequencies causing the coherent mixing of excitations.

Activity in certain living systems can lead to swirling flows akin to turbulence. Here, the authors connect the dynamics of topological defects in starfish oocyte membranes to vortex dynamics in 2D Bose–Einstein condensates.

Majorana bound states at the end of nanowires may be used for quantum computation if they can be coupled sufficiently strongly. Here, the Copenhagen lab show strong and tunable coupling, a step along the road towards devices.

A detailed and systematic X-ray and neutron scattering study of hexagonal iron sulfide uncovers the critical role of spin–phonon coupling in promoting the metal–insulator transition in this system.

A kind of quantum metasurface made of an atom array is proposed, providing the possibility to control both spatiotemporal and quantum properties of transmitted and reflected light.

Determining the properties that emerge from the equations that govern turbulent flow is a fundamental challenge in non-equilibrium physics. A hydrodynamic theory for two-dimensional active nematic fluids at vanishing Reynolds number is now put forward, revealing a universal scaling behaviour for this class of systems.

A general mechanism through which elastic filaments suspended in a strong compressional flow buckle and spontaneously acquire a chiral helicoidal shape is uncovered and elucidated theoretically.

Laboratory experiments reproduce the three-dimensional pancake-like shape of Jupiter’s vortices. The thickness of the Great Red Spot is predicted, awaiting comparison with NASA’s Juno mission.

As a unit for enzyme activity, the katal is enigmatic but struggles to find widespread acceptance. Soumitra Athavale tells its story.