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Category: particle physics

Ytterbium atomic clock could open a new window on fundamental physics

For the first time, an international team of physicists has successfully harnessed a rare orbital transition in atoms of ytterbium to create a new type of atomic clock that is both highly precise and extremely sensitive to fundamental physical effects. Publishing their results in Nature Photonics, the researchers, led by Taiki Ishiyama at Kyoto University, say their approach could pave the way for some of the most stringent tests yet of predictions made by the Standard Model.

To measure the passing of time, an atomic clock excites an electron in confined atoms to a higher energy level, then interrogates the transition frequency of the atoms. Because these oscillations display such little variation, atomic clocks are the most accurate timekeepers ever developed.

To date, the most precise devices involve atoms trapped in an optical lattice: a periodic array of light and darkness created by interfering laser beams. These clocks operate at optical frequencies with hundreds of trillions of oscillations per second—far surpassing the microwave frequencies used in previous atomic clock designs. Already, this extraordinary precision has enabled sensitive tests of fundamental physics, as described by the Standard Model.

Gravity from positivity: Single massive spin-3/2 particle makes gravity logically inevitable, study claims

Researchers at IPhT (CEA, CNRS) and the Universitat Autònoma de Barcelona have shown that gravity—and with it, supersymmetry—emerge as logical necessities whenever a massive spin-3/2 particle exists in nature. Two principles are enough: causality, the fact that no signal can travel faster than light, and unitarity, the requirement that probabilities are conserved in quantum mechanics. The structure of supergravity is not assumed: it bootstraps itself.

In fundamental physics, gravity is usually thought of as an ingredient one adds to a theory. But could it instead be forced by the internal consistency of the quantum world? This is what a study published in the Journal of High Energy Physics demonstrates.

The starting point is disarmingly simple: a single massive spin-3/2 particle. The authors show that such a particle simply cannot exist in isolation within a consistent theory. Its scattering amplitudes grow too fast with energy, clashing with positivity inequalities—the mathematical encoding of causality (the speed of light as an absolute limit) and unitarity (the conservation of probabilities in every quantum process). The theory breaks down barely above the particle’s own mass.

Underground lab clears crucial hurdle for dark matter hunt

Australia’s bid to detect elusive dark matter has taken a major step forward, with new research confirming that cosmic radiation levels deep inside the Stawell Underground Physics Laboratory (SUPL) are low enough to support the world-class experiment that will commence later this year.

ARC Center of Excellence for Dark Matter Particle Physics researchers recorded muon —or cosmic radiation—levels inside and outside the laboratory for more than a year. They detected 30,000 muons inside the underground laboratory, while 8.4 billion muons would be expected to be detected on the surface of Earth.

The SABRE Collaboration paper, published in Astroparticle Physics, is the first to use data collected in SUPL, marking a major achievement for Australian and international scientists involved in the project.

The secrets of black holes and the Higgs mass could be hidden in a 7-dimensional geometry

One of the greatest mysteries of modern physics, the “black hole information paradox,” might have finally found an elegant solution, and the answer could also reveal the origins of the mass of fundamental particles.

In the 1970s, Stephen Hawking demonstrated, through semi-classical calculations, that black holes are not truly black, but emit a weak radiation that causes them to gradually shrink until they disappear.

This process, however, brings with it a massive problem: it seems to cause an irreversible loss of information, violating the unitarity principle of quantum mechanics. In other words, the laws of quantum physics state that information cannot be destroyed, but the evaporation of a black hole suggests otherwise.

A tiny detector for microwave photons could advance quantum tech

Detecting a single particle of light is hard; detecting a single microwave photon is even harder. Microwave photons, the tiny packets of electromagnetic radiation used in current technologies like Wi-Fi and radar, carry far less energy than visible light. They are about 100,000 times weaker than optical photons.

Many existing quantum technologies depend on detecting individual photons with high reliability. For visible light, this is well established using devices that convert incoming light directly into electrical signals. But at microwave frequencies (0.3–30 GHz), this fails because each individual photon doesn’t carry enough energy to release an electric charge into a material. This means that detecting single microwave photons requires a completely different strategy.

A long-standing goal has been to realize a simple device capable of continuously detecting microwave photons. Now, scientists at EPFL, led by Pasquale Scarlino, have developed a semiconductor-based detector that takes an important step in that direction.

Small quantum system outperforms large classical networks in real-world forecasting

Can a handful of atoms outperform a much larger digital neural network on a real-world task? The answer may be yes. In a study published in Physical Review Letters, a team led by Prof. Peng Xinhua and Assoc. Prof. Li Zhaokai from the University of Science and Technology of China of the Chinese Academy of Sciences demonstrated that a quantum processor comprising just nine interacting spins outperforms classical networks with thousands of nodes in realistic weather forecasting tasks.

By exploiting unique quantum features such as superposition and entanglement, quantum devices offer new ways to represent and process information.

Recent experiments have shown their advantages in specialized benchmark tasks, but extending these gains to real-world applications remains a challenge. In particular, many quantum approaches rely on complex circuits that are difficult to implement accurately on today’s noisy hardware.

Proton-trapping MNene transforms ammonia production for food security and economic growth

With a new electrochemical synthesis via an electrochemical nitrogen reduction reaction (NRR), achieving carbon-free ammonia production is closer to reality through work from Drs. Abdoulaye Djire and Perla Balbuena, chemical engineering professors at Texas A&M University, and graduate students David Kumar and Hao En Lai. A topic outlined in their recent paper published in the Journal of the American Chemical Society introduces NRR, which produces ammonia in a cleaner and simpler way by using renewable electricity.

The research branches off of the team’s previous work, where they looked further into enabling two-dimensional materials in renewable energy.

“The current process of making ammonia is energy intensive and emits a lot of carbon dioxide, so if you can make ammonia electrochemically, then you can avoid these two negative effects,” Djire said. “During the electrochemical NRR process, water provides the hydrogen atoms, which combine with nitrogen from the air to form ammonia, all powered by electricity.”

A New Probe of Nanoparticle Melting

Understanding nanoparticles is important in astrophysics and atmospheric physics and for applications like catalysts. These particles are tough to characterize, but now Vitaly Kresin of the University of Southern California and his colleagues have determined one elusive property with high accuracy. They inferred the melting point of sodium and potassium nanoparticles 7–9 nm in diameter with an accuracy of 1% [1]. They found that the melting point is about 100 K lower than in bulk samples, in agreement with less-precise data on other types of nanoparticles of this size and with theoretical predictions. The technique could potentially provide a new way to probe other properties of nanoparticles having a wide range of sizes.

Metal nanoparticles are known to melt at lower temperatures than bulk samples, but the theory needed to predict the melting point has significant uncertainties. Experiments also face various challenges, such as the tendency of electron microscopes to melt nanoparticles. Kresin and his colleagues suspected that the work function—the energy required to remove an electron from a surface or a nanoparticle—might show some notable changes when a nanoparticle melts, given the major structural rearrangements involved.

Their recently developed setup [2] uses a beam of temperature-controlled nanoparticles targeted by an adjustable-wavelength, monochromatic light source. When the photons eject electrons, the team detects the charged particles. For both sodium and potassium, the work function-versus-temperature data show a clear discontinuity and change in slope at the melting point.

Ghostly particles: Dark radiation may have masqueraded as neutrinos

New research suggests that neutrinos in the early universe may have transformed into a previously unknown form of radiation. A study from Washington University in St. Louis offers a new way to explain certain puzzling observations about how the universe evolved.

Bhupal Dev and his colleagues report the results in a paper published in Physical Review Letters. Dev is an associate professor of physics in Arts & Sciences and a fellow of the McDonnell Center for the Space Sciences, both at WashU.

Neutrinos are among the most abundant particles in the universe. Often described as ghostlike because they interact so weakly with matter, neutrinos play an important role in shaping how cosmic structures form and evolve.

NOAA’s Space Weather Mission: Protecting Artemis II Astronauts and Society

For the majority of its orbit, the moon remains outside Earth’s magnetic field and is directly exposed to the full force of the solar wind and energetic solar particles. Artemis II astronauts will therefore spend time outside this naturally occurring protective shield. Any overlap between periods of heightened solar activity and time spent beyond Earth’s magnetospheric protection could pose significant radiation risks to the crew.

NASA relies on operational space weather forecasts and warnings from NOAA’s Space Weather Prediction Center (SWPC). As the nation’s official around-the-clock space weather forecasting authority, SWPC provides direct, real-time support to human spaceflight missions. Observations from NOAA’s GOES satellites and the SOLAR-1 observatory at Lagrange point 1 will provide important measurements of solar wind speed, magnetic field orientation, and the flow of hazardous, high-energy particles. These observations allow SWPC to issue timely warnings if radiation levels approach thresholds that could affect astronaut safety. During the Artemis II mission, NOAA forecasters will continuously monitor solar wind conditions and evaluate any solar flares, coronal mass ejections (CMEs), or solar energetic particle events that may occur.

The Solar Ultraviolet Imager (SUVI), Extreme Ultraviolet and X-Ray Irradiance Sensors (EXIS), Space Environment In-Situ Suite (SEISS), and Magnetometer (MAG) are specialized instruments onboard the GOES-R Series satellites that measure solar activity and changes in Earth’s magnetic field. Additionally, the Compact Coronagraph (CCOR-1) onboard GOES-19 further enhances the detection of CMEs by providing continuous real-time monitoring of the sun’s corona, improving both measurement quality and warning lead time.

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