Physics News and Discussions

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Experimental evidence for long-distance electrodynamic intermolecular forces
https://phys.org/news/2022-02-experimen ... cular.html
by Thamarasee Jeewandara , Phys.org
While classical and quantum electrodynamics present the existence of dipole-dipole long-range electrodynamics forces, they remain to be experimentally observed. The discovery of completely new and unanticipated forces that are present between biomolecules have considerable impact to understand the dynamics of molecular machines at work within living organisms. In a new report now published in Science Advances, Mathias Lechelon and a research team at the French National Centre for Scientific Research (CNRS) France conducted two independent experiments based on different physical effects, which they detected via fluorescence correlation spectroscopy and terahertz spectroscopy, respectively, to demonstrate experimental activation of resonant electrodynamic intermolecular forces. The outcomes provided unprecedented experimental proof-of-principle of a physical phenomenon with importance in biology. According to the study, aside from thermal fluctuations that randomly drove molecular motion, resonant and selective electrodynamic forces contributed to molecular encounters in crowded cellular spaces.
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Vacuum fluctuations break topological protection
https://phys.org/news/2022-03-vacuum-fl ... gical.html
by An­dreas Trabe­singer, ETH Zurich
A hallmark of so-called topological quantum states is that they are protected against local perturbations. ETH physicists now demonstrate that in the paradigmatic case of the integer quantum Hall effect, vacuum fluctuations can cause a breakdown of topological protection.

"Up to 1980 nobody expected that there exists an effect like the Quantized Hall Effect, which depends exclusively on fundamental constants and is not affected by irregularities in the semiconductor like impurities or interface effects." So spoke the German physicist Klaus von Klitzing on receiving the 1985 Nobel Prize in Physics. He was recognized for his discovery, in 1980, of a quantised version of the Hall effect in two-dimensional electron gasses. The unexpected robustness of the 'integer quantum Hall effect', as it has become known, in fact enabled von Klitzing's discovery in the first place. He was working with semiconductors—materials famously plagued by imperfections—yet observed an astonishingly 'clean' quantization of the Hall conductivity. The fact that such quantum systems can be so well protected against local perturbations was later explained in the framework of topological properties of electronic many-body states. But that protection can break down in unexpected ways, as the group of Prof. Jérôme Faist at the Institute of Quantum Electronics now reports. Writing in Science, they present experiments in which they established that exposing a quantum Hall system to the strongly enhanced quantum vacuum fluctuations of a tight cavity provides a novel and potentially general route to substantially modify quantum states. Such 'vacuum-field engineering' might lead to new experimental capability—but could also cause unwanted interference in experiments combining two-dimensional materials and resonators.
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caltrek
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Event Horizons are Tunable Factories of Quantum Entanglement
March 4, 2022

https://www.eurekalert.org/news-releases/945484

Introduction:
(EurekAlert) LSU physicists have leveraged quantum information theory techniques to reveal a mechanism for amplifying, or “stimulating,” the production of entanglement in the Hawking effect in a controlled manner. Furthermore, these scientists propose a protocol for testing this idea in the laboratory using artificially produced event horizons. These results have been recently published in Physical Review Letters, “Quantum aspects of stimulated Hawking radiation in an analog white-black hole pair,” where Ivan Agullo, Anthony J. Brady and Dimitrios Kranas present these ideas and apply them to optical systems containing the analog of a pair white-black hole.

Black holes are some of the most mystifying objects in our universe, largely due to the fact that their inner-workings are hidden behind a completely obscuring veil — the black hole’s event horizon.

In 1974, Stephen Hawking added more mystique to the character of black holes by showing that, once quantum effects are considered, a black hole isn’t really black at all but, instead, emits radiation, as if it was a hot body, gradually losing mass in the so-called “Hawking evaporation process.” Further, Hawking’s calculations showed that the emitted radiation is quantum mechanically entangled with the bowels of the black hole itself. This entanglement is the quantum signature of the Hawking effect. This astounding result is difficult, if not impossible, to be tested on astrophysical black holes, since the faint Hawking radiation gets overshined by other sources of radiation in the cosmos.

On the other hand, in the 1980’s, a seminal article by William Unruh established that the spontaneous production of entangled Hawking particles occurs in any system that can support an effective event horizon. Such systems generally fall under the umbrella of “analog gravity systems” and opened a window for testing Hawking's ideas in the laboratory.

Serious experimental investigations into analog gravity systems — made of Bose-Einstein condensates, non-linear optical fibers, or even flowing water — have been underway for more than a decade. Stimulated and spontaneously-generated Hawking radiation has recently been observed in several platforms, but measuring entanglement has proved elusive due to its faint and fragile character.
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weatheriscool
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Physicists show how frequencies can easily be multiplied without special circuitry
https://phys.org/news/2022-03-physicist ... uitry.html
by Martin-Luther-Universität Halle-Wittenberg
A new discovery by physicists at Martin Luther University Halle-Wittenberg (MLU) could make certain components in computers and smartphones obsolete. The team has succeeded in directly converting frequencies to higher ranges in a common magnetic material without the need for additional components. Frequency multiplication is a fundamental process in modern electronics. The team reports on its research in the latest issue of Science.

Digital technologies and devices are already responsible for about ten percent of global electricity consumption, and the trend is rising sharply. "It is therefore necessary to develop more efficient components for information processing," says Professor Georg Woltersdorf, a physicist from MLU.

Non-linear electronic circuits are typically used to generate the high-frequency gigahertz signals needed to operate today's devices. The team at MLU has now found a way to do this within a magnetic material without the electronic components that are usually used for this. Instead, the magnetization is excited by a low-frequency megahertz source. Using the newly discovered effect, the source generates several frequency components, each of which is a multiple of the excitation frequency. These cover a range of six octaves and reach up to several gigahertz. "This is like hitting the lowest note on a piano while also hearing the corresponding harmonic tones of the higher octaves," explains Woltersdorf.
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caltrek
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University of Nevada, Las Vegas Researchers Discover New Form of Ice
March 18, 2022

[url][https://www.eurekalert.org/news-releases/946973/url]

Introduction:
(EurekAlert) UNLV researchers have discovered a new form of ice, redefining the properties of water at high pressures.

Solid water, or ice, is like many other materials in that it can form different solid materials based on variable temperature and pressure conditions, like carbon forming diamond or graphite. However, water is exceptional in this aspect as there are at least 20 solid forms of ice known to us.

A team of scientists working in UNLV’s Nevada Extreme Conditions Lab pioneered a new method for measuring the properties of water under high pressure. The water sample was first squeezed between the tips of two opposite-facing diamonds—freezing into several jumbled ice crystals. The ice was then subjected to a laser-heating technique that temporarily melted it before it quickly re-formed into a powder-like collection of tiny crystals.

By incrementally raising the pressure, and periodically blasting it with the laser beam, the team observed the water ice make the transition from a known cubic phase, Ice-VII, to the newly discovered intermediate, and tetragonal, phase, Ice-VIIt, before settling into another known phase, Ice-X.

Zach Grande, a UNLV Ph.D. student, led the work which also demonstrated that the transition to Ice-X, when water stiffens aggressively, occurs at much lower pressures than previously thought.
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New experiment could confirm the fifth state of matter in the universe
https://phys.org/news/2022-03-state-universe.html
by University of Portsmouth
An experiment that could confirm the fifth state of matter in the universe—and change physics as we know it—has been published in a new paper from the University of Portsmouth.

Physicist Dr. Melvin Vopson has already published research suggesting that information has mass and that all elementary particles, the smallest known building blocks of the universe, store information about themselves, similar to the way humans have DNA.

Now, he has designed an experiment—which if proved correct—means he will have discovered that information is the fifth form of matter, alongside solid, liquid, gas and plasma.

Dr. Vopson said: "This would be a eureka moment because it would change physics as we know it and expand our understanding of the universe. But it wouldn't conflict with any of the existing laws of physics.

"It doesn't contradict quantum mechanics, electrodynamics, thermodynamics or classical mechanics. All it does is complement physics with something new and incredibly exciting."

Dr. Vopson's previous research suggests that information is the fundamental building block of the universe and has physical mass.

He even claims that information could be the elusive dark matter that makes up almost a third of the universe.

He said: "If we assume that information is physical and has mass, and that elementary particles have a DNA of information about themselves, how can we prove it? My latest paper is about putting these theories to the test so they can be taken seriously by the scientific community."
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Quantum physics sets a speed limit to electronics
https://phys.org/news/2022-03-quantum-p ... onics.html
by Vienna University of Technology
How fast can electronics be? When computer chips work with ever shorter signals and time intervals, at some point they come up against physical limits. The quantum-mechanical processes that enable the generation of electric current in a semiconductor material take a certain amount of time. This puts a limit to the speed of signal generation and signal transmission.

TU Wien (Vienna), TU Graz and the Max Planck Institute of Quantum Optics in Garching have now been able to explore these limits: The speed can definitely not be increased beyond one petahertz (one million gigahertz), even if the material is excited in an optimal way with laser pulses. This result has now been published in the scientific journal Nature Communications.
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raklian
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Gas made out of photons? That's pretty... photon-y.

To know is essentially the same as not knowing. The only thing that occurs is the rearrangement of atoms in your brain.
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Engineering quantum states in solids using light
https://phys.org/news/2022-03-quantum-s ... olids.html
by Pohang University of Science & Technology
A POSTECH research team led by Professor Gil-Ho Lee and Gil Young Cho (Department of Physics) has developed a platform that can control the properties of solid materials with light and measure them.

Recognized for developing a platform to control and measure the properties of materials in various ways with light, the findings from the study were published in the journal Nature on March 15, 2022.

The electrical properties of a material are determined by the movement of electrons in the material. For example, a material is defined as a metal if electrons can move freely; otherwise, it is an insulator. In order to change the electrical properties of these solids, applying heat or pressure or adding impurities have been generally used. This is because the change in the position of the atoms in the solid changes the movement of electrons accordingly.
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Lottery luck in the light of physics: Researchers present theory on the dynamics of many-particle systems
https://phys.org/news/2022-03-lottery-l ... amics.html
by Bayreuth University
Physicists at the University of Bayreuth are among the international pioneers of power functional theory. This new approach makes it possible for the first time to precisely describe the dynamics of many-particle systems over time. The particles can be atoms, molecules or larger particles invisible to humans. The new theory generalizes the classical density functional theory, which only applies to many-particle systems in thermal equilibrium. In Reviews of Modern Physics, a research team led by Prof. Dr. Matthias Schmidt presents the basic features of the theory, which was significantly developed and elaborated in Bayreuth.

A many-particle system is in thermal equilibrium when the temperature in its interior is balanced and no heat flows take place. This does not necessarily mean that the system is in a rigid state of rest. Some many-particle systems can also be compared to a lottery draw machine, which rotates at a constant speed. The balls have a lot of freedom of movement in it and jump back and forth in a disorderly fashion. In a fluid many-particle system, the particles are packed considerably more densely than in the drum, which is why they constantly collide with each other at short distances and time intervals. Essential properties of such systems can be described completely and precisely with the density functional theory—provided that a thermal equilibrium of the system is given.

In the case of the lottery draw machine, this equilibrium is lost as soon as the uniform rotation gradually slows down and the chamber goes into reverse. Then the balls with the winning numbers roll onto a rail inside the chamber and are finally ejected. In order to record such processes precisely and without gaps, the power functional theory is needed: it translates the luck of the winners into the language of physics.
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