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Innovative optical atomic clock could combine single-ion accuracy with multi-ion stability

For many years, cesium atomic clocks have been reliably keeping time around the world. But the future belongs to even more accurate clocks: optical atomic clocks. In a few years’ time, they could change the definition of the base unit second in the International System of Units (SI). It is still completely open, which of the various optical clocks will serve as the basis for this.

The large number of optical clocks that the Physikalisch-Technische Bundesanstalt (PTB), as a leading institute in this field, has realized could be joined by another type: an optical multi-ion clock with ytterbium-173 ions. It could combine the high accuracy of individual ions with the improved stability of several ions. This is the result of a cooperation between PTB and the Thai metrology institute NIMT.

The team led by Tanja Mehlstäubler reports on this in the current issue of the journal Physical Review Letters. The results are also interesting for quantum computing and, with a new look inside the atom, for fundamental research.

Nature-inspired ‘POMbranes’ could transform water recycling in textile and pharma industries

Scientists have collaborated to develop a new class of highly precise filtration membranes. The research, published in the Journal of the American Chemical Society, could significantly reduce energy consumption and enable large-scale water reuse in industry. The team includes researchers from the CSIR-Central Salt and Marine Chemicals Research Institute (CSMCRI), Indian Institute of Technology Gandhinagar, the Nanyang Technological University, Singapore, and the S N Bose National Centre for Basic Sciences.

Everyday industrial processes, like purifying medicines, cleaning textile dyes, and processing food, rely on “separations.” Currently, these processes are incredibly energy-hungry, accounting for nearly 40% to 50% of all global industrial energy use. Most factories still use old-fashioned methods like distillation and evaporation to separate ingredients, which are expensive and leave a heavy carbon footprint.

Although membrane-based technologies are considered cleaner, most polymer membranes currently used in industry have irregularly sized pores that tend to degrade over time, limiting their effectiveness. Thus, they lack the precision and long-term stability needed for demanding industrial applications.

Brain navigation study reveals function of an unconventional electrical-signaling mode in neurons

Navigating the world is no mean feat, especially when the world pushes back. For instance, airflow hitting a fly on its right side can, after a turn, become a headwind. To stay on course, the fly’s brain must interpret sensations that constantly shift with each turn of its body.

Indeed, transforming changing sensory inputs into a more stable, map-like understanding of the world is intimately connected to an animal’s ability to survive and navigate within its environment. How do flies make it look so easy?

Now, a study published in Cell shows that the fly brain uses a surprisingly economical strategy. Earlier work had demonstrated that flies calculate their direction of travel by combining four neural signals, each encoding motion along a different axis. The new research finds that when it comes to wind direction, the brain doesn’t need four neuronal populations, but only two. This is because each population can handle two opposite directions in the wind system.

New cryogenic vacuum chamber cuts noise for quantum ion trapping

Even very slight environmental noise, such as microscopic vibrations or magnetic field fluctuations a hundred times smaller than Earth’s magnetic field, can be catastrophic for quantum computing experiments with trapped ions.

To address that challenge, researchers at the Georgia Tech Research Institute (GTRI) have developed an improved cryogenic vacuum chamber that helps reduce some common noise sources by isolating ions from vibrations and shielding them from magnetic field fluctuations. The new chamber also incorporates an improved imaging system and a radio frequency (RF) coil that can be used to drive ion transitions from within the chamber.

“There’s a lot of excitement around quantum computing today, and trapped ions are just one of the research platforms available, each with their own benefits and drawbacks,” explained Darian Hartsell, a GTRI research scientist who leads the project. “We are trying to mitigate multiple sources of noise in this chamber and make other improvements with one robust new design.”

Optical technique reveals hidden magnetic states in antiferromagnets

Imagine computer hardware that is blazing fast and stores more data in less space. That’s the promise of antiferromagnets, magnetic materials that do not interfere with each other and can switch states at high speed, opening the door to advanced computing and quantum applications.

Magnetism comes from unpaired electrons, tiny particles that orbit an atom’s nucleus. Each electron has a property called spin, which can point up or down. In standard ferromagnets, the atomic spins point in the same direction, creating a strong magnetic field. In antiferromagnets, neighboring spins point in opposite directions, canceling each other out and yielding no net magnetism.

Flipping individual spins in an antiferromagnet requires very little movement of magnetization, which allows ultrafast processing. Antiferromagnets can switch states trillions of times per second, compared with billions for ferromagnets. With net zero magnetism, antiferromagnets can be placed very close together without repelling or attracting each other, allowing more data to be stored in a small space.

Metal clumps in a quantum state: Physicists place thousands of sodium atoms in a ‘Schrödinger’s cat state’

Can a small lump of metal be in a quantum state that extends over distant locations? A research team at the University of Vienna answers this question with a resounding yes. In the journal Nature, physicists from the University of Vienna and the University of Duisburg-Essen show that even massive nanoparticles consisting of thousands of sodium atoms follow the rules of quantum mechanics. The experiment is currently one of the best tests of quantum mechanics on a macroscopic scale.

In quantum mechanics, not only light but also matter can behave both as a particle and as a wave. This has been proven many times for electrons, atoms, and small molecules through double-slit diffraction or interference experiments. However, we do not see this in everyday life: marbles, stones, and dust particles have a well-defined location and a predictable trajectory; they follow the rules of classical physics.

At the University of Vienna, the team led by Markus Arndt and Stefan Gerlich has now demonstrated for the first time that the wave nature of matter is also preserved in massive metallic nanoparticles. The scale of the particles is impressive: the clusters have a diameter of around 8 nanometers, which is comparable to the size of modern transistor structures.

EAST achieves new plasma confinement regime using small 3D magnetic perturbations

A research group has achieved a new plasma confinement regime using small 3D magnetic perturbations that simultaneously suppress edge instabilities and enhance core plasma confinement in the Experimental Advanced Superconducting Tokamak (EAST). The research results are published in PRX Energy.

Sustained high plasma confinement at both the core and the edge without edge crash events due to edge instabilities is critical for efficient fusion energy production in tokamaks. However, achieving stable, high-core confinement with an internal transport barrier (ITB) is extremely challenging, especially in tungsten-wall devices where tungsten impurity accumulation must be controlled. Furthermore, controlling edge instabilities usually results in degraded core plasma confinement.

In this study, the researchers applied small 3D magnetic perturbations localized at the plasma edge. This method achieved the suppression of edge instabilities and control of tungsten impurities. For the first time, it also enabled the induction and sustained confinement of high-core plasma with an ITB.

Velocity gradients prove key to explaining large-scale magnetic field structure

All celestial bodies—planets, suns, even entire galaxies—produce magnetic fields, affecting such cosmic processes as the solar wind, high-energy particle transport, and galaxy formation. Small-scale magnetic fields are generally turbulent and chaotic, yet large-scale fields are organized, a phenomenon that plasma astrophysicists have tried explaining for decades, unsuccessfully.

In a paper published January 21 in Nature, a team led by scientists at the University of Wisconsin–Madison have run complex numerical simulations of plasma flows that, while leading to turbulence, also develop structured flows due to the formation of large-scale jets. From their simulations, the team has identified a new mechanism to describe the generation of magnetic fields that can be broadly applied, and has implications ranging from space weather to multimessenger astrophysics.

“Magnetic fields across the cosmos are large-scale and ordered, but our understanding of how these fields are generated is that they come from some kind of turbulent motion,” says the study’s lead author Bindesh Tripathi, a former UW–Madison physics graduate student and current postdoctoral researcher at Columbia University.

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