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Category: particle physics – Page 526

Oxidation numbers have so far eluded any rigorous quantum mechanical definition. A new SISSA study, published in Nature Physics, provides such a definition based on the theory of topological quantum numbers, which was honored with the 2016 Nobel Prize in Physics, awarded to Thouless, Haldane and Kosterlitz. This result, combined with recent advances in the theory of transport achieved at SISSA, paves the way to an accurate, yet tractable, numerical simulation of a broad class of materials that are important in energy-related technologies and planetary sciences.

Every undergraduate student in the natural sciences learns how to associate an integer oxidation number to a chemical species participating in a reaction. Unfortunately, the very concept of oxidation state has thus far eluded a rigorous quantum mechanical definition, so that no method was known until now to compute oxidation numbers from the fundamental laws of nature, let alone demonstrate that their use in the simulation of charge transport does not spoil the quality of numerical simulations. At the same time, the evaluation of electric currents in ionic conductors, which is required to model their transport properties, is presently based on a cumbersome quantum-mechanical approach that severely limits the feasibility of large-scale computer simulations. Scientists have lately noticed that a simplified model where each atom carries a charge equal to its oxidation number may give results in surprising good agreement with rigorous but much more expensive approaches.

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Researchers at the University of Southampton and the Korea Institute for Advanced Study have recently showed that supersymmetry is anomalous in N=1 superconformal quantum field theories (SCFTs) with an anomalous R symmetry. The anomaly described in their paper, published in Physical Review Letters, was previously observed in holographic SCFTs at strong coupling, yet their work confirms that it is already present in the simplest free STFCs.

“Supersymmetry is a symmetry that relates particles with integer and half-integer spin, and has played a central role in many advances in since its discovery,” Kostas Skenderis, one of the researchers who carried out the study, told Phys.org. “It has been used as a means to understand the behavior of strongly interacting where our usual theoretical tools () are not applicable, as well as in some of the main candidates for beyond the Standard Model physics.”

Supersymmetry underlies the mathematical consistency of string theory, which is the most complete theory of gravity proposed so far. A quantum anomaly, such as that observed by the researchers, is essentially the failure of a symmetry to be preserved at a quantum level. These anomalies typically come in two types: “bad” ones, which render string theory mathematically inconsistent and “healthy” ones, which capture important quantum properties of the theory.

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It actually makes more sense that all the foundational physics laws do not exist but somehow they do. That is why I still believe there is some governing force that controls the parameters possibly. It makes more sense that our universe somehow was not created than it all somehow just magically sustained itself. That is why I think aliens created the universe as a containment possibly or that the laws of physics somehow are not completely know of how they all work together. Some talk about super symmetry but still seems some sorta things are still not know and we may never know until the theory of everything can be created.

Our best theories predict that all the matter in the universe should have been destroyed as soon as it existed. So how comes there’s something, not nothing?

By Daniel Cossins

Mystery: Why does anything exist at all?

THERE is plenty to recommend the standard model, our best description of particles and their interactions. But it has the odd awkward lapse. “It is a somewhat embarrassing fact that it fails to explain our existence,” says Werner Rodejohann at the Max Planck Institute for Nuclear Physics in Germany.

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Structured light beams can serve as vortex beams carrying optical angular momentum and have been used to enhance optical communications and imaging. Rego et al. generated dynamic vortex pulses by interfering two incident time-delayed vortex beams with different orbital angular momenta through the process of high harmonic generation. A controlled time delay between the pulses allowed the high harmonic extreme-ultraviolet vortex beam to exhibit a time-dependent angular momentum, called self-torque. Such dynamic vortex pulses could potentially be used to manipulate nanostructures and atoms on ultrafast time scales.

Science, this issue p. eaaw9486.

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Physicists at the National Institute of Standards and Technology (NIST) have teleported a computer circuit instruction known as a quantum logic operation between two separated ions (electrically charged atoms), showcasing how quantum computer programs could carry out tasks in future large-scale quantum networks.

Quantum teleportation transfers data from one quantum system (such as an ion) to another (such as a second ion), even if the two are completely isolated from each other, like two books in the basements of separate buildings. In this real-life form of teleportation, only quantum information, not matter, is transported, as opposed to the Star Trek version of “beaming” entire human beings from, say, a spaceship to a planet.

Teleportation of quantum data has been demonstrated previously with ions and a variety of other quantum systems. But the new work is the first to teleport a complete quantum logic operation using ions, a leading candidate for the architecture of future quantum computers. The experiments are described in the May 31 issue of Science.

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In conventional imaging methods, a beam of photons (or other particles) is reflected off the object to be imaged. After the beam travels to a detector, the information gathered there is used to create a photograph or other type of image. In an alternative imaging technique called “ghost imaging,” the process works a little differently: an image is reconstructed from information that is detected from a beam that never actually interacts with the object.

The key to is to use two or more correlated beams of particles. While one interacts with the object, the second beam is detected and used to reconstruct the image, even though the second beam never interacts with the object. The only aspect of the first beam that is detected is the arrival time of each photon on a separate detector. But because the two beams are correlated, the image of the object can be fully reconstructed.

While two beams are usually used in ghost imaging, recent research has demonstrated higher-order correlations—that is, correlations among three, four, or five beams. Higher-order ghost imaging can lead to improvements in image visibility, but it comes with the drawback that higher-order correlated events have a lower probability of detection, which causes lower resolution.

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Circa 2014

A team of researchers from Princeton University has started doing some very strange things with light. Instead of letting it zip by at incredibly high speed, they’re stopping it dead: freezing it into crystal.

Crucially, they’re not shining light through crystal; rather, they making light into crystal. It’s a process that involves fixing the particles of light known as photons in a single spot, freezing them permanently in one place. It’s never been done before, and it could help develop new exotic materials with weird and wonderful properties.

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