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Category: particle physics

Ultrafast X-rays allow researchers to ‘watch’ how molecules rearrange during a chemical reaction controlled by light

Since the 1980s, researchers have sought to use laser light to control chemical reactions relevant to photochemistry, catalysis and light-responsive materials. But this technique, known as coherent control, has a blind spot: There has been no way to directly see the molecules in these reactions as their structures rearrange.

Now, researchers at the Department of Energy’s SLAC National Accelerator Laboratory have imaged a coherently controlled chemical reaction for the first time. Their work, published in Physical Review A, uses ultrafast X-rays from the Linac Coherent Light Source (LCLS) to show in real time how atoms move in a molecule that was excited and manipulated with laser light.

“There are many challenges with controlling chemical reactions, but seeing is believing,” said study lead author Tom Hopper, assistant professor at the University of Central Florida who was a postdoctoral researcher at SLAC at the time of the study. “If you can see something directly, it opens up a new level of control.”

A new quantum computer sets a high watermark for accuracy. Are we on the verge of a big breakthrough?

In a laboratory in Broomfield, Colorado, 98 atoms are suspended in midair, held in place by electric fields and cooled to temperatures close to absolute zero.

Each atom is far smaller than anything the naked eye could ever see, yet each carries information in a form that has no counterpart in classical physics.

Together, they form Helios, a new quantum computer built by the British-American company Quantinuum. Quantum computers use the power of quantum mechanics, the rules that govern how physics operates at atomic and subatomic scales. Those that use Helios’ model of suspended atoms are known as trapped-ion.

Interlayer self-doping could unlock room-temperature multiferroics in atom-thin materials

Multiferroics are materials that exhibit more than one prominent “ferroic” property, such as ferromagnetism and ferroelectricity. One of their most advantageous features is that they allow engineers to control their magnetic states with electric fields or vice versa, due to an effect known as magnetoelectric coupling.

NASA’s Cold Atom Lab is creating one of the weirdest forms of matter in space

NASA’s upgraded Cold Atom Lab is turning the International Space Station into a frontier for quantum research, creating ultra-cold matter that behaves in astonishing ways. The experiments could unlock new discoveries about the universe while paving the way for powerful future technologies in space and on Earth.

Homing pigeon navigation relies on superparamagnetic macrophages under overcast conditions

Birds use a variety of navigational strategies, including the geomagnetic field, especially when other cues are not available, such as under overcast or nocturnal conditions. Magnetite particles in the beak, cryptochromes in the eye, cellular ion-channel alterations, and changes in the vestibular system have been proposed to explain magnetoreception, but the exact mechanisms remain debated. Here, we used physical, morphological, functional, and genomic assays to identify the presence of superparamagnetic macrophages in the liver. We found that after macrophage depletion, pigeons flying under overcast conditions lacked their usual orientation capabilities. Orientation was unimpaired in birds without macrophages when the sun was visible, suggesting that this was their primary cue.

Can String Theory Be Explained with No Strings Attached?

Using a “bootstrap” approach, researchers show that a small set of assumptions may naturally lead to a string-theory description of certain high-energy processes.

String theory has been a remarkably influential conceptual framework for modern theoretical physics. While its description of nature in terms of tiny strings captures the imagination, the string framework has had profound impact in a broad range of subfields, going well beyond its lead role as a viable theory of quantum gravity. For instance, it has led to deeper understanding of black holes and their relation to entanglement and quantum information [1], and it has provided theoretical benchmarks for explaining quark–gluon plasma observations in quantum chromodynamics [2]. As a complement to direct calculations, theoretical physicists would like to understand string theory as emerging from a set of fundamental principles that any theory of nature must respect. Consistency with these bedrock conditions, so goes the idea, could perhaps make string theory inevitable.

Electron-Ion Collider’s radiofrequency controls system passes first real-world test

The U.S. Department of Energy’s (DOE) Brookhaven National Laboratory has reached a key early milestone in developing radiofrequency control systems for the Electron-Ion Collider (EIC)—a next-generation research facility that will collide electrons with ions to reveal how the building blocks of matter are held together.

At the heart of any particle accelerator are radiofrequency (RF) systems, which use electromagnetic waves to accelerate particle beams to near-light speed and keep them tightly controlled. The system tested here—known as low-level radiofrequency (LLRF)—acts as the “brain,” precisely controlling those RF fields to ensure stable and accurate operation.

This milestone marks the first successful test of the newly built EIC common platform-based LLRF electronics on a real accelerator cavity. The common platform is a shared hardware and control system for accelerator operations, allowing teams to use the same technology rather than create separate electronics for each system.

A minimal model for how a cell takes shape from the inside

Researchers at the University of Twente and Utrecht University have packed rigid, rod-shaped particles into soft lipid containers the size of a living cell and watched the container and its contents reshape each other. The vesicle’s form determines how the rods line up; the tightly packed rods, in turn, bend the container into new shapes. This provides a minimal model for how physical coupling between a soft boundary and internal filaments can help cellular structures organize from within. The paper is published in the Proceedings of the National Academy of Sciences.

Living cells are crowded with filaments. These threadlike scaffolds hold a cell in shape, push it forward when it moves and pull it apart when it divides, all inside a soft membrane that bends and flows around them. The filaments shape the membrane, and the membrane in turn constrains the filaments.

Physicists understand one half of that exchange, but mostly for rigid containers. Pack enough rod-shaped particles into a fixed box and they switch from a disordered jumble to neat alignment, much like matches settling when you shake the box. What happens when the container can give way had barely been tested. A flexible wall can deform to make room for its contents, so the familiar rules no longer hold.

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