Physics News and Discussions

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Experiment verifies a connection between quantum theory and information theory

https://phys.org/news/2024-12-quantum-theory.html

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Particle that only has mass when moving in one direction observed for first time
https://phys.org/news/2024-12-particle-mass.html
by Adrienne Berard, Pennsylvania State University

For the first time, scientists have observed a collection of particles, also known as a quasiparticle, that's massless when moving one direction but has mass in the other direction. The quasiparticle, called a semi-Dirac fermion, was first theorized 16 years ago, but was only recently spotted inside a crystal of semi-metal material called ZrSiS. The observation of the quasiparticle opens the door to future advances in a range of emerging technologies from batteries to sensors, according to the researchers.

The team, led by scientists at Penn State and Columbia University, recently published their discovery in the journal Physical Review X.

Join our new WhatsApp channel! Stay up-to-date on the latest science news from Science X.

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MIT Physicists Control Magnetism With Light
The researchers used a terahertz laser to control magnetic spin inside antiferromagnetic materials.
By Ryan Whitwam December 23, 2024
https://www.extremetech.com/science/mit ... with-light

Scientists from MIT have been blasting magnets with lasers, which is more scientific than it sounds. Researchers working with antiferromagnetic material have devised a way to control the magnetic states of atoms with a super-fast laser. With the precise control over atomic spin demonstrated in this work, it may be possible to develop a new generation of more durable and efficient magnetic data storage.

Everyone knows what a magnet is, but what about an antiferromagnet? Magnetic materials get their attractive properties from the orientation of atomic spin. In a magnet, the spin is aligned in the same way so the material can be influenced by an external magnetic field. However, an antiferromagnet is composed of atoms with alternating spin—one pointing up, then one down, then up, and so on. This averages out to net zero magnetization.

Researchers have long believed that antiferromagnets could serve as a next-generation alternative to traditional magnetic storage media. However, the problem has always been in how you write data by switching up its magnetic states. That's where the laser comes in.

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Mathematical methods point to possibility of particles long thought impossible
https://phys.org/news/2025-01-mathemati ... ought.html
by George Hale, Rice University

From the early days of quantum mechanics, scientists have thought that all particles can be categorized into one of two groups—bosons or fermions—based on their behavior.

However, new research by Rice University physicist Kaden Hazzard and former Rice graduate student Zhiyuan Wang shows the possibility of particles that are neither bosons nor fermions. Their study, published in Nature, mathematically demonstrates the potential existence of paraparticles that have long been thought impossible.

"We determined that new types of particles we never knew of before are possible," said Hazzard, associate professor of physics and astronomy.

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Quantum breakthrough may lead to sustainable chiral spintronics
https://phys.org/news/2025-01-quantum-b ... onics.html
by Jay Mwamba, City College of New York

A team of physicists led by The City College of New York's Lia Krusin-Elbaum has developed a novel technique that uses hydrogen cations (H+) to manipulate relativistic electronic bandstructures in a magnetic Weyl semimetal—a topological material where electrons mimic massless particles called Weyl fermions. These particles are distinguished by their chirality or "handedness" linked to their spin and momentum.

In the magnetic material MnSb₂Te₄, researchers unveiled a fascinating ability to "tune" and enhance the chirality of electronic transport by introducing hydrogen ions, reshaping on-demand the energy landscapes—called Weyl nodes—within the material. This finding could open a breadth of new quantum device platforms for harnessing emergent topological states for novel chiral nano-spintronics and fault-tolerant quantum computing. Entitled "Transport chirality generated by a tunable tilt of Weyl nodes in a van der Waals topological magnet," the study appears in the journal Nature Communications.

The tuning of Weyl nodes with H+ heals the system's (Mn-Te) bond disorder and lowers the internode scattering. In this process—which The City College team tests in the Krusin Lab using angularly-resolved electrical transport—electrical charges move differently when the in-plane magnetic field is rotated clockwise or counterclockwise, generating desirable low-dissipation currents. The reshaped Weyl states feature a doubled Curie temperature and a strong angular transport chirality synchronous with a rare field-antisymmetric longitudinal resistance—a low-field tunable 'chiral switch' that is rooted in the interplay of topological Berry curvature, chiral anomaly and a hydrogen-mediated form of Weyl nodes.

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Newly fabricated crystals control interactions between high-frequency phonons and single quantum systems
https://phys.org/news/2025-01-newly-fab ... -high.html
by Ingrid Fadelli , Phys.org

Phonons, the quantum mechanical vibrations of atoms in solids, are often sources of noise in solid-state quantum systems, including quantum technologies, which can lead to decoherence and thus adversely impact their performance.

Strategies to reliably control phonons and their interactions with quantum systems could help to mitigate the adverse effects of these vibrations on the systems.

Researchers at Harvard University and other institutes have introduced a new approach to control the interactions between high-frequency phonons and single solid-state quantum systems. Their proposed method, outlined in a paper published in Nature Physics, relies on new diamond phononic crystals that they designed and fabricated, which can be used to engineer the local density of states in a host material.

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Superfluid spirals: Scientists control Kelvin waves for first time

by Tejasri Gururaj , Phys.org

In a new study published in Nature Physics, researchers have developed the first controlled method for exciting and observing Kelvin waves in superfluid helium-4.

First described by Lord Kelvin in 1880, Kelvin waves are helical (spiral-shaped) waves that travel along the vortex lines, playing a vital role in how energy dissipates in quantum systems. However, they are difficult to study experimentally.

Creating a controlled setting to observe them has been the biggest challenge that the researchers overcame. Phys.org spoke to the first author of the study, Associate Prof. Yosuke Minowa from Kyoto University.

The discovery came about through serendipity. "We applied an electric field to a nanoparticle decorating a quantized vortex, hoping to translate the entire structure. Instead, we observed a clear wavy motion of the vortex core, namely Kelvin wave excitation. This unexpected result prompted us to shift our focus toward studying the excitation of Kelvin waves in-depth," said Prof. Minowa.

The heart of the experiment lies in the properties of superfluids.

https://phys.org/news/2025-01-superflui ... elvin.html

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A Quantum Demonic Engine Doesn’t Have to Violate Thermodynamics to Work
by Dr Alfredo Carpineti
February 11, 2025

Introduction:

(IFL Science) The second law of thermodynamics underpins all of classical reality. It is the reason why it's easier to make things messy, why you can’t have perpetual motion, why you age, and maybe even why time only moves in one direction. There have been considerations that the quantum world might escape the constraints of this law. New work reveals that this is indeed possible, but also it doesn’t look like quantum mechanics has to break this crucial law to work.

The example taken by this international team of scientists is Maxwell’s demon, probably the most famous thought experiment on the second law of thermodynamics. Imagine two chambers filled with gas divided by a small door. The demon has keen senses and can detect the energy of the molecules. By opening and closing the door, it divides the cold and hot portions of the gas, creating a system with lower entropy – the disorder of the system – and that would break the second law.

In the classical world, a realistic demon would not break the second law – there’s the mechanical work of the door, the information in the demon’s mind, etc. It all adds up to the total entropy. However, it turns out that it is possible to break it in quantum mechanics. The team developed a "demonic engine" – a system that could measure a target system, extract work by coupling it to a thermal environment, and then erase its memory using that thermal environment.

The team expected that they would find that the engine always needs more energy coming in than what they can get out. This is the cornerstone of the second law. Instead, they were able to find theoretical exceptions.

“Our results showed that under certain conditions permitted by quantum theory, even after accounting for all costs, the work extracted can exceed the work expended, seemingly violating the second law of thermodynamics,” lead author Shintaro Minagawa, from Nagoya University, said in a statement. “This revelation was as exciting as it was unexpected, challenging the assumption that quantum theory is inherently ‘demon-proof.’ There are hidden corners in the framework where Maxwell’s Demon could still work its magic.”

Read more here: https://www.iflscience.com/a-quantum-d ... ork-78001

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Measuring the 'size' of a neutrino: Physicists suggest it's considerably larger than an atomic nucleus

https://phys.org/news/2025-02-size-neut ... arger.html

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Physicists Uncover Evidence of Two Arrows of Time Emerging from the Quantum Realm
February 13, 2025

Introduction:

(Eurekalert) What if time is not as fixed as we thought? Imagine that instead of flowing in one direction – from past to future – time could flow forward or backwards due to processes taking place at the quantum level. This is the thought-provoking discovery made by researchers at the University of Surrey, as a new study reveals that opposing arrows of time can theoretically emerge from certain quantum systems.

For centuries, scientists have puzzled over the arrow of time – the idea that time flows irreversibly from past to future. While this seems obvious in our experienced reality, the underlying laws of physics do not inherently favour a single direction. Whether time moves forward or backwards, the equations remain the same.

Dr Andrea Rocco, Associate Professor in Physics and Mathematical Biology at the University of Surrey and lead author of the study, said:

“One way to explain this is when you look at a process like spilt milk spreading across a table, it's clear that time is moving forward. But if you were to play that in reverse, like a movie, you'd immediately know something was wrong – it would be hard to believe milk could just gather back into a glass.

“However, there are processes, such as the motion of a pendulum, that look just as believable in reverse. The puzzle is that, at the most fundamental level, the laws of physics resemble the pendulum; they do not account for irreversible processes. Our findings suggest that while our common experience tells us that time only moves one way, we are just unaware that the opposite direction would have been equally possible."

Read more here: https://www.eurekalert.org/news-releases/1073595

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New X-ray experiment could solve major physics puzzles

https://phys.org/news/2025-02-ray-major ... zzles.html

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Plastic ice VII: Exotic substance likely found in space created in the lab
By Michael Irving
February 20, 2025
https://newatlas.com/science/exotic-pla ... i-created/

Water ice is a far more complex substance than we might assume. Scientists have now created an exotic new form of ice in the lab, known as “plastic ice VII.” This strange version could exist naturally on other planets and moons in our solar system.

The ice in your drinks – and pretty much everywhere else on the surface of Earth – is technically referred to as ice I, but the scientific census actually goes all the way up to ice XIX. These strange types of ice have different crystalline structures and properties, and form under a variety of pressure and temperature conditions.

Contrary to what you might expect, plastic ice VII isn’t the seventh form of plastic ice. Instead, it’s a plastic version of ice VII, a type that’s often created in the lab and has been found deep beneath Earth’s surface. As opposed to ice I’s hexagonal crystalline structure, ice VII has a cubic structure.

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Scientists map the forces acting inside a proton
https://phys.org/news/2025-02-scientists-proton.html
by Rhiannon Koch, University of Adelaide

Scientists have now mapped the forces acting inside a proton, showing in unprecedented detail how quarks—the tiny particles within—respond when hit by high-energy photons.

The international team includes experts from the University of Adelaide who are exploring the structure of sub-atomic matter to try and provide further insight into the forces that underpin the natural world.

"We have used a powerful computational technique called lattice quantum chromodynamics to map the forces acting inside a proton," said Associate Professor Ross Young, Associate Head of Learning and Teaching, School of Physics, Chemistry and Earth Sciences, who is part of the team.

"This approach breaks down space and time into a fine grid, allowing us to simulate how the strong force—the fundamental interaction that binds quarks into protons and neutrons—varies across different regions inside the proton."

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Scientists map the forces acting inside a proton

https://phys.org/news/2025-02-scientists-proton.html

Einstein wins again! Quarks obey relativity laws, Large Hadron Collider finds

https://www.space.com/Quark-Large-Hadro ... s-Einstein

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New theory suggests star mergers produce universe's highest-energy particles

https://phys.org/news/2025-03-theory-st ... ghest.html

SciAm- Einstein’s General Relativity with a Twist: Teleparallelism

https://archive.ph/XVUSO

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New superconducting state discovered: Cooper-pair density modulation
https://phys.org/news/2025-03-supercond ... nsity.html
by Kimm Fesenmaier, California Institute of Technology

Superconductivity is a quantum physical state in which a metal is able to conduct electricity perfectly without any resistance. In its most familiar application, it enables powerful magnets in MRI machines to create the magnetic fields that allow doctors to see inside our bodies. Thus far, materials can only achieve superconductivity at extremely low temperatures, near absolute zero (a few tens of Kelvin or colder).

But physicists dream of superconductive materials that might one day operate at room temperature. Such materials could open entirely new possibilities in areas such as quantum computing, the energy sector, and medical technologies.

"Understanding the mechanisms leading to the formation of superconductivity and discovering exotic new superconducting phases is not only one of the most stimulating pursuits in the fundamental study of quantum materials but is also driven by this ultimate dream of achieving room-temperature superconductivity," says Stevan Nadj-Perge, professor of applied physics and materials science at Caltech.

Now a team led by Nadj-Perge that includes Lingyuan Kong, AWS quantum postdoctoral scholar research associate, and other colleagues at Caltech has discovered a new superconducting state—a finding that provides a new piece of the puzzle behind this mysterious but powerful phenomenon. A paper about the work was published on March 19 in the journal Nature.

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Hot Schrödinger cat states created
https://phys.org/news/2025-04-hot-schrd ... tates.html
by University of Innsbruck

Quantum states can only be prepared and observed under highly controlled conditions. A research team from Innsbruck, Austria, has now succeeded in creating so-called hot Schrödinger cat states in a superconducting microwave resonator. The study, published in Science Advances, shows that quantum phenomena can also be observed and used in less perfect, warmer conditions.

Schrödinger cat states are a fascinating phenomenon in quantum physics in which a quantum object exists simultaneously in two different states. In Erwin Schrödinger's thought experiment, it is a cat that is alive and dead at the same time.

In real experiments, such simultaneity has been seen in the locations of atoms and molecules and in the oscillations of electromagnetic resonators.

Previously, these analogs to Schrödinger's thought experiment were created by first cooling the quantum object to its ground state, the state with the lowest possible energy.

Now, researchers led by Gerhard Kirchmair and Oriol Romero-Isart have demonstrated for the first time that it is indeed possible to create quantum superpositions from thermally excited states.

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Enhanced CsPbBr₃ X-ray detectors achieve record-low detection limits
https://phys.org/news/2025-04-cspbbr-ra ... imits.html
by Zhang Nannan, Chinese Academy of Sciences

In a major step forward for radiation detection technology, a research team led by Prof. Meng Gang from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences has significantly enhanced the performance of CsPbBr3-based X-ray detectors by dramatically lowering their detection limit and suppressing noise and ion migration through innovative cooling and defect-passivation strategies.

Their work, published in Applied Physics Letters and Advanced Functional Materials, lays the groundwork for the next generation of safer and more precise X-ray imaging technology.

One of the biggest challenges in utilizing CsPbBr3 for X-ray detectors has been minimizing noise and improving sensitivity.

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Layered room-temperature altermagnet shows promise for advanced spintronics
https://phys.org/news/2025-04-layered-r ... anced.html
by Ingrid Fadelli , Phys.org

Traditionally, magnetic materials have been divided into two main categories: ferromagnets and antiferromagnets. Over the past few years, however, physicists have uncovered the existence of altermagnets, a new type of magnetic material that exhibits features of both antiferromagnets and ferromagnets.

Altermagnets are magnetic materials that have no net magnetization (i.e., their atomic magnetic moments cancel each other out), like antiferromagnets. Yet they also break spin degeneracy (i.e., the usual energy equality between spin-up and spin-down electrons), similarly to ferromagnets.

Researchers at Songshan Lake Materials Laboratory, Southern University of Science and Technology, the Hong Kong University of Science and Technology and other institutes in China recently set out to realize a layered altermagnet that can generate non-collinear spin current. The room-temperature metallic altermagnet they unveiled was outlined in a paper published in Nature Physics.