Physics News and Discussions

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Elusive romance of top-quark pairs observed at Large Hadron Collider

https://phys.org/news/2025-07-elusive-r ... large.html
An unforeseen feature in proton-proton collisions previously observed by the CMS experiment at CERN's Large Hadron Collider (LHC) has now been confirmed by its sister experiment ATLAS.

The result, reported yesterday at the European Physical Society's High-Energy Physics conference in Marseille, suggests that top quarks—the heaviest and shortest-lived of all the elementary particles—can momentarily pair up with their antimatter counterparts to produce a "quasi-bound-state" called toponium. Further input based on complex theoretical calculations of the strong nuclear force—called quantum chromodynamics (QCD)—will enable physicists to understand the true nature of this elusive dance.

High-energy collisions between protons at the LHC routinely produce top quark–antiquark pairs. Measuring the probability, or cross section, of this process is both an important test of the Standard Model of particle physics and a powerful way to search for the existence of new particles that are not described by the theory.

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New quantum record: Transmon qubit coherence reaches millisecond threshold
https://phys.org/news/2025-07-quantum-t ... econd.html
by Aalto University

On July 8, 2025, physicists from Aalto University in Finland published a transmon qubit coherence measurement in Nature Communications that dramatically surpasses previous scientifically published records. The millisecond coherence measurement marks a quantum leap in computational technology, with the previous maximum echo coherence measurements approaching 0.6 milliseconds.

Longer qubit coherence allows for an extended window of time in which quantum computers can execute error-free operations, enabling more complex quantum computations and more quantum logic operations before errors occur. Not only does this allow for more calculations with noisy quantum computers, but it also decreases the resources needed for quantum error correction, which is a path to noiseless quantum computing.

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Higgs-boson properties clarified through decay pattern analysis

by CERN
https://phys.org/news/2025-07-higgs-bos ... ttern.html

The ATLAS collaboration finds evidence of Higgs-boson decays to muons and improves sensitivity to Higgs-boson decays to a Z boson and a photon.

Studies of the properties of the Higgs boson featured prominently in the program of the major annual physics conference, the 2025 European Physical Society Conference on High Energy Physics (EPS-HEP), held this week in Marseille, France. Among the results presented by the ATLAS collaboration were two results narrowing in on two exceptionally rare Higgs-boson decays.

The first process under study was the Higgs-boson decay into a pair of muons (H→μμ). Despite its scarceness—occurring in just 1 out of every 5000 Higgs decays—this process provides the best opportunity to study the Higgs interaction with second-generation fermions and shed light on the origin of mass across different generations. Up to now, the interactions of the Higgs boson with matter particles have only been observed for particles from the third, heaviest, generation: the tau lepton and the top and bottom quarks.

Can the Large Hadron Collider snap string theory?

by Nathi Magubane, University of Pennsylvania
https://phys.org/news/2025-07-large-had ... heory.html

In physics, there are two great pillars of thought that don't quite fit together. The Standard Model of particle physics describes all known fundamental particles and three forces: electromagnetism, the strong nuclear force, and the weak nuclear force. Meanwhile, Einstein's general relativity describes gravity and the fabric of spacetime.

However, these frameworks are fundamentally incompatible in many ways, says Jonathan Heckman, a theoretical physicist at the University of Pennsylvania. The Standard Model treats forces as dynamic fields of particles, while general relativity treats gravity as the smooth geometry of spacetime, so gravity "doesn't fit into physics's Standard Model," he explains.

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Researchers demonstrate room-temperature lasing in photonic-crystal surface-emitting laser

by Jeni Bushman, University of Illinois Grainger College of Engineering
https://phys.org/news/2025-07-room-temp ... ystal.html

In a first for the field, researchers from The Grainger College of Engineering at the University of Illinois Urbana-Champaign have reported a photopumped lasing from a buried dielectric photonic-crystal surface-emitting laser emitting at room temperature and an eye-safe wavelength. Their findings, published in IEEE Photonics Journal, improve upon current laser design and open new avenues for defense applications.

For decades, the lab of Kent Choquette, professor of electrical and computer engineering, has explored VCSELs, a type of surface-emitting laser used in common technology like smartphones, laser printers, barcode scanners, and even vehicles. But in early 2020, the Choquette lab became interested in groundbreaking research from a Japanese group that introduced a new type of laser called photonic-crystal surface-emitting lasers, or PCSELs.

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Scientists achieve first experimental observation of the transverse Thomson effect
https://phys.org/news/2025-07-scientist ... ffect.html
by Tejasri Gururaj, Phys.org

In a new Nature Physics paper, researchers report the first experimental observation of the transverse Thomson effect, a key thermoelectric phenomenon that has eluded scientists since it was predicted over a century ago.

For over a century, thermoelectric effects have formed the foundation of how physicists understand the link between heat and electricity. Our knowledge of how heat and electricity interact within materials is rooted in the Seebeck, Peltier, and Thomson effects, all identified during the 1800s.

The Thomson effect causes volumetric heating or cooling when an electric current and a temperature gradient flow in the same direction through a conductor.

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CERN Physicists Find Key Piece of the Matter-Antimatter Puzzle
In a first, CERN physicists succeeded in observing matter-antimatter imbalance in baryons, fundamental particles that make up most of the observable universe.

All matter in our universe has an evil twin: antimatter. Cosmological models suggest that the Big Bang should have created equal amounts of matter and antimatter that cancel each other out. But for reasons physicists still aren’t completely sure about, that didn’t happen. As a result, our universe today hosts slightly more matter than antimatter—our very existence being clear, physical proof.

Now, we might be one step closer to explaining why there’s an imbalance between matter and antimatter, an unsolved mystery in physics formally known as the charge-parity (CP) violation, or CP asymmetry. In a paper published today in Nature, researchers at the Large Hadron Collider beauty (LHCb) Collaboration at CERN, Switzerland, report the first experimental verification of the CP violation in the decay of baryons—fundamental particles that make up most matter in the observable universe. The results were announced earlier this year at the Rencontres de Moriond conference.

https://gizmodo.com/cern-physicists-fin ... 2000629084

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Spin currents control device magnetization using low-cost materials
https://phys.org/news/2025-07-currents- ... rials.html
by University of Minnesota

This low-symmetry material produces powerful spin-orbit torque (SOT)—a key mechanism for manipulating magnetism in next-generation memory and logic technologies. Credit: The Nano Magnetism and Quantum Spintronics Lab/University of Minnesota Twin Cities

Research from the University of Minnesota Twin Cities gives new insight into a material that could make computer memory faster and more energy-efficient.

The study was recently published in Advanced Materials, a peer-reviewed scientific journal. The researchers also have a patent on the technology.

As technology continues to grow, so does the demand for emerging memory technology. Researchers are looking for alternatives and complements to existing memory solutions that can perform at high levels with low energy consumption to increase the functionality of everyday technology.

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Quantum Internet Meets Space-time in this New Ingenious Idea
July 14, 2025

Introduction:

(Eurekalert) Hoboken, N.J., July 14, 2025 — Quantum networking is being rapidly developed world-wide. It is a key quantum technology that will enable a global quantum internet: the ability to deploy secure communication at scale, and to connect quantum computers globally. The race to realize this vision is in full swing, both on Earth and in space.

Now, a new research result, developed in a collaboration between Igor Pikovski at Stevens Institute of Technology, Jacob Covey at the University of Illinois at Urbana-Champaign and Johannes Borregaard at Harvard University, suggests that quantum networks are more versatile than previously thought. In the paper titled Probing Curved Spacetime with a Distributed Atomic Processor Clock, just published in the journal PRX Quantum, the researchers show that this technology can probe how curved space-time affects quantum theory — a first test of this kind.

Quantum physics has passed every test with flying colors so far. But how it behaves when Einstein’s theory of gravity —general relativity — comes into the picture is less clear. In Einstein’s theory, gravity is no longer a force, but a result of changing space and time — curved space-time. This leads to unique effects, such as the slowing of time near planets. The phenomenon has been measured, and confirmed, to very high accuracy, as well as popularized in science-fiction films and novels like Interstellar. But how does this changing flow of time affect quantum mechanics? Could quantum theory or general relativity, or both, require modification where they intertwine? While a full theory of quantum gravity remains lacking, there are suggestions that quantum principles might change in the presence of curved spacetime. However, probing this frontier was so far impossible in experiments.

In a previous study titled Testing Quantum Theory on Curved Spacetime with Quantum Networks that appeared on May 27 in Physical Review Research, Pikovski and Borregaard have shown that the time is ripe for experiments to explore these questions, using quantum networks.

Read more here: https://www.eurekalert.org/news-releases/1090481

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Physicists discover aluminum-20, a new three-proton-emitting isotope

by Zhang Nannan, Chinese Academy of Sciences
https://phys.org/news/2025-07-physicist ... otope.html

Radioactive decay is a fundamental process in nature by which an unstable atomic nucleus loses energy by radiation. Studying nuclear decay modes is crucial for understanding properties of atomic nuclei. In particular, exotic decay modes like proton emission provide essential spectroscopic tools for probing the structure of nuclei far from the valley of stability—the region containing stable nuclei on the nuclear chart.

In a study published in Physical Review Letters on July 10, physicists from the Institute of Modern Physics (IMP) of the Chinese Academy of Sciences (CAS) and their collaborators have reported the first observation and spectroscopy of aluminum-20, a previously unknown and unstable isotope that decays via the rare process of three-proton emission.

"Aluminum-20 is the lightest aluminum isotope that has been discovered so far. Located beyond the proton drip line, it has seven fewer neutrons than the stable aluminum isotope," said Associate Prof. Xu Xiaodong from IMP, first author of the study.

Using an in-flight decay technique at the Fragment Separator of the GSI Helmholtz Center for Heavy Ion Research in Darmstadt, Germany, the researchers measured angular correlations of aluminum-20's decay products and discovered the previously unknown nucleus aluminum-20.

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More on that by the uni:

https://news.emory.edu/features/2025/07 ... index.html

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Quantum entanglement lasts 600 times longer in elusive dark states, study finds

by JooHyeon Heo, Ulsan National Institute of Science and Technology
https://phys.org/news/2025-09-quantum-e ... -dark.html
edited by Sadie Harley, reviewed by Robert Egan

A research team affiliated with UNIST has successfully demonstrated the experimental creation of collective quantum entanglement rooted in dark states—previously confined to theoretical models. The findings are published online in Nature Communications.

Unlike bright states, dark states are highly resistant to external disturbances and exhibit remarkably extended lifetimes, making them promising candidates for next-generation quantum technologies such as quantum memory and ultra-sensitive sensors.

Led by Professor Je-Hyung Kim in the Department of Physics at UNIST, in collaboration with Dr. Changhyoup Lee from the Korea Research Institute of Standards and Science (KRISS) and Dr. Jin Dong Song from the Korea Institute of Science and Technology (KIST), the team has achieved the controlled induction of dark state-based collective entanglement. Remarkably, this entanglement exhibits a lifetime approximately 600 times longer than that of conventional bright states.

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Novel hollow-core optical fiber transmits data 45% faster with record low loss

September 2, 2025

Despite the modern world relying heavily on digital optical communication, there has not been a significant improvement in the minimum attenuation—a measure of the loss of optical power per kilometer traveled—of optical fibers in around 40 years. Decreasing this loss would mean that the signal could travel further without being amplified, leading to more data being transmitted over longer distances, faster internet and more efficient networks.

Current fibers transmit light through silica cores, which have limited room for loss improvement. Another option is the hollow-core fiber (HCF), which theoretically allows for faster speeds due to the ability of light to travel faster through air than through silica. Still, scientists struggled to design HCFs that actually performed better than silica-based cables. In most cases, the attenuation was worse or the design was impractical.

But now, researchers from the University of Southampton and Microsoft claim to have made a breakthrough in HCF design in a recently published study in Nature Photonics. The new fiber achieves a record low loss of 0.091 dB/km at 1,550 nm, compared to a 0.14 dB/km minimum loss for silica-based fibers. The new design maintains low losses of around 0.2 dB/km over a 66 THz bandwidth and boasts 45% faster transmission speeds.

[...]

The team believes that further research can reduce losses even more, possibly down to 0.01 dB/km, and also help to tune the fiber for low-loss operation at different wavelengths. Even the losses achieved, however, open up the potential for longer unamplified spans in undersea and terrestrial cables and high-power laser delivery and sensing applications, among others.

The authors end by saying, "In light of the reported results, we are confident that, with advancements in produced volumes, geometrical consistency and reduced presence of absorbing gases in the core, DNANF HCFs will establish themselves as a pivotal waveguiding technology. This innovation has the potential to enable the next technological leap in data communications."

https://phys.org/news/2025-09-hollow-co ... smits.html

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