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Learning may rely on stronger neural connections, not expanding networks

How does the brain learn? Does it acquire new knowledge by creating new neural pathways or by strengthening existing connections? A new study from Bar-Ilan University offers evidence in favor of the latter, suggesting that learning is driven primarily by changes in the strength of existing neural connections rather than by expanding the brain’s underlying architecture.

Published in Physica A: Statistical Mechanics and its Applications, the study by Prof. Ido Kanter of Bar-Ilan University’s Department of Physics and the Gonda (Goldschmied) Multidisciplinary Brain Research Center explored this longstanding question using artificial neural networks trained on language-learning tasks.

As the amount of training data increased, the models became significantly better at learning. Surprisingly, however, the researchers found that the networks could still lose roughly the same proportion of connections (synapses) without any meaningful decline in performance. In other words, improved learning did not depend on building more complex networks. Instead, it resulted from more effective cooperation among the components that were already there.

Cesium atoms and quantum dots generate indistinguishable photons for modular quantum networks

Large-scale quantum communication networks require both reliable quantum memories and coherent single-photon sources that can exchange quantum information efficiently. A coherent source of single photons with narrow linewidth, high brightness, spectral uniformity and compatibility with quantum memories is necessary. While a variety of single-photon sources, such as quantum dots (QDs) and atoms in warm vapor cells, have been developed in recent years, each has inherent limitations, making a scalable and functional quantum network challenging to achieve.

Hybrid quantum architectures that combine different quantum light sources can address these challenges. For example, QDs, which suffer from spectral randomness and are not well suited for photon storage, can be paired with atomic systems that provide reliable frequency standards and quantum memories. In such architectures, QDs can serve as bright, high-rate photon sources, while atomic systems handle photon storage and synchronization.

However, a key challenge in realizing such hybrid quantum architectures is interfacing different quantum light sources. Single photons emitted from different sources exhibit distinct spatial and temporal properties, necessitating modifications and synchronization that introduce losses and increase resource needs.

New microwave neural network method could compress and secure wireless communications

One year after unveiling a first-of-its-kind “microwave brain” microchip capable of computing on ultrafast data and wireless signals, researchers from the Cornell Duffield College of Engineering have shown how the chip can encode information into its own language.

The work builds on the world’s first integrated microwave neural network designed by Bal Govind, Ph.D., and experimentally demonstrated with Maxwell Anderson. Together, they showed that the low-power chip could harness the physics of microwaves to emulate the brain’s pattern-finding abilities and perform computations almost instantaneously.

In a new study published in Nature Communications, the researchers found that the device can now use what they describe as microwave token embeddings—similar to the tokens used in large language models—to encode messages into radio signals and compress data, capabilities that could enable faster, more secure communications for satellites, drones and other technologies.

Physicists create Bose–Einstein condensate from ultracold polar molecules

Bose–Einstein condensates are states of matter that form when particles called bosons are cooled to temperatures that are only a fraction of a degree above absolute zero (i.e., 0 Kelvin [-460°F]). In these states, particles occupy the same quantum state and exhibit interesting collective behaviors, essentially behaving as if they were a single “super-particle.”

So far, physicists have primarily created Bose–Einstein condensates using atoms. The first realization of these states with molecules was just over two decades ago, in 2003.

Producing Bose–Einstein condensates with ultracold polar molecules, cooled molecules in which positive and negative charges are separate, has proved particularly challenging. This is partly due to chemical reactions that can cause a loss of these molecules while they are being cooled.

Neutrons reveal how friction stir welding could strengthen steel armor

Using neutrons at the Department of Energy’s Oak Ridge National Laboratory, researchers from The Ohio State University are studying residual stress caused by friction stir welding (FSW) to reveal how to strengthen armor steel welds, like those used in military vehicles. Their findings were published in the Journal of Materials Processing Technology.

“We are trying to develop a new way to join armor steel that produces joints with better ballistic and blast performance,” said Antonio Ramirez, a professor of materials science and engineering at OSU. “In the end, we want to be able to make structures that perform better.”

The team’s results will help fine-tune welding parameters to create a roadmap for engineering better armor systems.

Light’s hidden properties save quantum information from the chaos of bad weather

For years, researchers have tried to harness the “twist” of light to transmit data. This property describes how light spirals as it travels forward, and because it can be molded into a virtually infinite number of different twists, it provides a massive, promising alphabet for high-capacity communication.

This twisted light has proven notoriously fragile in real-world environments such as bad weather, atmospheric turbulence and water. Once it passes through these chaotic media, the twisted pattern becomes completely unrecognizable, a major historical barrier that has stalled the use of this large alphabet for global communications.

By sending quantum information through a storm, researchers at The University of the Witwatersrand in Johannesburg, South Africa, have shown that the information in light can be kept completely intact, even though the light itself was completely warped beyond recognition.

Neutron star collisions may forge gold more slowly than expected

Where do gold, platinum and uranium come from? This question has fascinated astrophysicists and nuclear physicists for decades. A research team from Technische Universität Darmstadt has now taken an important step toward understanding the origin of heavy elements. Their findings are published in Physical Review Letters.

Approximately half of all elements heavier than iron are produced through the rapid neutron-capture process, commonly known as the r-process. This process occurs under extreme conditions, such as during the collision of two neutron stars. In these events, atomic nuclei are bombarded with neutrons at an extraordinary rate, enabling the formation of increasingly heavier elements.

A major challenge is that many of the nuclei involved are extremely neutron-rich and cannot be studied experimentally in laboratories. Scientists therefore rely on theoretical models, whose predictions often diverge significantly when applied to regions far from experimentally known nuclei. Some of these exotic nuclei can be produced at research facilities such as GSI/FAIR, but many remain beyond experimental reach.

One LED produces four stable colors at room temperature

Full-color displays normally require separate red, green and blue light emitters. A team from the University of Osaka and Ritsumeikan University has demonstrated another approach: a single light-emitting layer that produces several colors when electrically powered at room temperature. The study was published in Applied Physics Letters.

Micro-LED displays promise high brightness, energy efficiency and resolution. However, conventional green and red nitride LEDs can show changes in color as the current increases. Producing several colors also generally requires multiple light-emitting layers or separately manufactured chips, making it difficult to place many pixels into a very small area.

The team used a manufacturing method already widely employed for nitride LEDs to create aluminum gallium nitride LEDs containing terbium ions.

New twist on the Einstein problem reveals unexpected physics

A shape that captured worldwide attention for solving a decades-old mathematical puzzle has returned to the spotlight. While the shape’s properties allowed it to solve previous puzzles, little is known about its other associated properties, creating opportunities for further discovery. These unexplored properties may also help solve new physics mysteries, such as how to twist light into striking chiral patterns.

In an article published in Nature Communications, researchers from the Institute of Industrial Science, The University of Tokyo, and collaborating institutions created optical structures based on the “Smith hat,” an unusual shape that solves the so-called Einstein problem in mathematics. By shining laser light onto these structures, the team discovered diffraction behaviors never before observed in conventional quasicrystals.

The long-standing Einstein problem asks whether a single tile shape, or “monotile,” can be used to cover an entire surface in a nonrepeating pattern. While periodic tilings such as honeycombs or checkerboards repeat regularly, an aperiodic monotile can cover all of space without ever producing a repeating arrangement. In 2023, the first such monotile, the Smith hat, was discovered, sparking widespread interest in the scientific community.

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