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Magnetic order survives weak quantum fluctuations in gapless magnets

In a new study published in Physical Review Letters, researchers have shown that magnetic order can survive weak quantum fluctuations in disordered magnets that lack an energy gap. The work establishes robust ferromagnetism in the two-dimensional random-bond quantum Ising model, confirming a longstanding conjecture in quantum statistical mechanics.

Many magnets owe their order to spontaneous symmetry breaking (SSB). Physicists have long sought to prove that this order is stable against perturbations such as quantum fluctuations. Existing proofs, however, typically require the system to have an energy gap. Disordered magnets such as the random-bond Ising model are gapless, placing them outside the reach of these proofs.

The researchers developed a proof technique that does not rely on an energy gap. They adapted an argument from statistical mechanics, known as the Peierls argument, to quantum systems.

New tool tracks a hidden protein involved in viral infection and cell cleanup

Viruses such as influenza A and dengue can hijack a cellular system that helps manage protein aggregates. Previous work by FMI emeritus group leader Patrick Matthias and his team showed that a small protein called ubiquitin plays an important role in this process.

The viruses rely on a free form of ubiquitin that is not attached to other proteins. This “unanchored” ubiquitin is also involved in immune responses and protein cleanup, but it has been difficult to study because researchers lack tools that can specifically detect it.

So, Matthias and collaborators at ETH Zurich set out to build a tool that could distinguish unanchored ubiquitin from other forms of the protein. Working with researchers in Guillaume Diss’s lab and the FMI structural biology facility, Longlong Wang—a former postdoc with Matthias—started with HDAC6, a protein that naturally binds unanchored ubiquitin. They improved the binding, then used computer-based protein design tools, including AlphaFold, to generate thousands of new versions. Their work is published in Science Advances.

Scientists find lunar ‘magnetic fossil’ in Chang’e-6 samples

The moon no longer has a global magnetic field, but lunar rocks and soils still contain records of ancient magnetism. Studying the magnetic minerals in these samples can help scientists understand how the moon’s magnetic field evolved over time.

Researchers examining impact-glass particles containing metallic iron from Chang’e-6 lunar soil samples discovered face-centered cubic γ-Fe—the first time this iron phase has been identified in natural lunar samples.

The study, led by professor Du Haifeng from the High Magnetic Field Laboratory of the Hefei Institutes of Physical Science (HFIPS) of the Chinese Academy of Sciences (CAS), was published in the Proceedings of the National Academy of Sciences on Sept. 16.

Spin rephasing helps quantum memories store single-photon states longer for future networks

We are continuously sending information to each other, transmitting zeros and ones through a giant network of connected computers and devices. Scientists are now trying to extend this familiar concept of the internet to the quantum realm, looking for an efficient way to exchange quantum rather than classical information: qubits instead of bits. The motivation is not just scientific curiosity. Qubits can be a 0, a 1 or any superposition of the two. They can also become entangled, showing a degree of correlation that is out of reach for classical bits.

A key element in enabling the quantum internet is the quantum repeater, an architecture aimed at distributing entanglement over long distances. Quantum repeaters, in turn, require quantum memories that can hold a quantum state long enough to synchronize measurements across different network segments and establish entanglement.

ICFO researchers Alberto Rodríguez Moldes, Dr. Félicien Appas, Jonathan Hänni, Dr. Jelena Rakonjac and Dr. Samuele Grandi, led by ICREA professor Hugues de Riedmatten, have taken a significant step in this direction. By implementing the so-called spin rephasing protocol, they have demonstrated that solid-state quantum memories—promising candidates for building quantum networks because of their proven high efficiency, capacity to store entanglement and multiplexing features—can store single photons for longer than previously possible. The results, published in Physical Review Letters and obtained within the Quantum Internet Alliance (QIA), bring us closer to the quantum internet.

Laser temporarily reprograms ultrathin optical device without electrodes

A tiny device that can be reprogrammed using a laser could lead to adaptable devices for computing, imaging and telecommunications. Most devices are built to perform a particular job. If you want them to do something different, you generally need to replace a component, rewire the system or manufacture a new one. For example, every time you ask a large language model like ChatGPT or Claude a question, many electrical signals race through computer chips, carrying information and performing calculations. This takes energy, and lots of it.

Scientists are always searching for faster and potentially more energy-efficient ways to process information. One possible solution is to replace some electrical signals with light.

An international team of researchers led by the ARC Center for Transformative Meta-Optical Systems (TMOS) at The Australian National University combined an ultrathin optical surface with liquid crystals, the material used in many electronic displays. The team collaborated with researchers at Nottingham Trent University in the U.K. and Friedrich Schiller University Jena in Germany.

Mapping one atom’s interaction with light uncovers an unbounded network of quantum states

A new graph-theoretic framework provides a unified description of atom-light interactions across regimes ranging from weak to deep-strong coupling.

A research team comprising professors Sunkyu Yu and Namkyoo Park of the Department of Electrical and Computer Engineering at Seoul National University College of Engineering and professor Xianji Piao of the University of Seoul has discovered that even the interaction between a single atom and light—one of the simplest settings in quantum physics—contains an enormous, intricately connected network.

The study was published Sept. 25 in the journal Science Advances.

Experimental evidence of altermagnetism in a layered material opens a promising path toward future spintronics

To build the ultrafast computers of the future, scientists are looking beyond the electrical charge of electrons to another property: their spin. While conventional hardware relies on the movement of charge to process data, tapping into this intrinsic quantum property could enable researchers to reinvent how information travels through a circuit.

Now, a team led by UCF physics professor Madhab Neupane has identified a promising candidate. Neupane and his collaborators found evidence of altermagnetism, an emerging form of magnetism that combines useful characteristics of two more familiar types: ferromagnetism and antiferromagnetism. Their paper is published in the journal Nature Communications.

Ferromagnetism produces the behavior most people associate with everyday magnets. In these materials, magnetic moments align in the same direction, creating a magnetic field. That property can be useful in electronics, but the resulting stray magnetic fields can interfere with nearby components.

Waves find order in the chaos of an oddly shaped cavity

When light or sound bounces around inside an oddly shaped room, its reflections can quickly become difficult to predict. But new research led by scientists at the Advanced Science Research Center at the CUNY Graduate Center (CUNY ASRC) shows that waves can behave very differently when they travel through a special class of materials.

The study, published in Nature Physics, demonstrates that waves inside an irregularly shaped cavity made from hyperbolic materials (named after the mathematical curve called a hyperbola because of the distinctive shape they force light waves to take) can organize into stable, repeating paths rather than scattering chaotically.

The researchers call these structures “hyperbolic wave attractors,” and their findings could eventually help scientists and engineers design new ways to control light, radio waves and sound in complex environments.

New model explains why glass becomes less transparent to terahertz light

Electromagnetic waves in the gigahertz (GHz) range, such as those used in mobile communications, can readily pass through many types of glass. However, transmission decreases significantly at terahertz frequencies above a characteristic threshold.

Although this phenomenon has been observed experimentally for some time, a quantitative model connecting it to the microscopic structure and dynamics of glass has been lacking.

To address this problem, the research team developed a continuum model that incorporates elastic heterogeneity in glass alongside microscopic charge fluctuations at atomic and molecular scales. The model describes how terahertz electromagnetic waves interact with vibrational dynamics in glass.

Rare quantum state reveals particles with quarter-electron charge

An electron’s charge is normally fixed, like a coin you can’t break into pieces. But if electrons are cooled close to absolute zero and trapped in a two-dimensional layer under a powerful magnetic field, they organize into a collective state of “quasiparticles” that seem to hold only a fraction of an electron’s charge.

This state is known as the “fractional quantum Hall effect.” A small number of these states, known as “even-denominator states,” have drawn attention because some theories predict they could contain unusual quasiparticles called “non-Abelian anyons.”

Why are these interesting? Because their quantum properties make them candidates for storing and processing information in fault-tolerant (error-resistant) topological quantum computers.

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