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Category: quantum physics – Page 20

Black-hole solutions in quantum gravity with Vilkovisky-DeWitt effective action

Physicists propose that calculations of certain aspects of quantum gravity can currently be done even without a full theory of quantum gravity itself. Basically, they work backwards from the fact that quantum gravity on the macro scale must conform to Einstein’s relativity theories. This approach is effective until the small scale of a black hole singularity is close.

(See my Comment below for an article link to POPULAR MECHANICS that discussed the scientific article in an accessible manner.

We study new black-hole solutions in quantum gravity. We use the Vilkovisky-DeWitt unique effective action to obtain quantum gravitational corrections to Einstein’s equations. In full analogy to previous work done for quadratic gravity, we find new black-hole–like solutions. We show that these new solutions exist close to the horizon and in the far-field limit.

Elusive romance of top-quark pairs observed at the LHC

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.

Last year, CMS researchers were analysing a large sample of top quark–antiquark production data collected from 2016 to 2018 to search for new types of Higgs bosons when they observed something unusual. The team saw a surplus of top quark–antiquark pairs, which is often considered as a smoking gun for the presence of new particles. Intriguingly, the excess appeared at the very minimum energy required to produce such a pair of top quarks. This led the team to consider an alternative hypothesis of something that had long been considered too difficult to detect at the LHC: a short-lived union of a top quark and a top antiquark.

Breakthrough battery lets physicists reverse entanglement—and rewrite quantum law

Scientists have finally uncovered a quantum counterpart to Carnot’s famed second law, showing that entanglement—once thought stubbornly irreversible—can be shuffled back and forth without loss if you plug in a clever “entanglement battery.”

An approach to realize heralded photon storage in a Rydberg superatom

Quantum technologies, systems that operate leveraging quantum mechanical effects, have the potential to outperform classical technologies in some specific tasks. Over the past decades, some researchers have also been trying to realize quantum networks, systems comprised of multiple connected quantum devices.

So far, have been the most widely used particles for carrying across different devices in quantum networks. The main reasons for this are that photons can travel at remarkable speeds, while weakly interacting with their surrounding environment, which helps to preserve the quantum states they are carrying.

To successfully employ photons in quantum networks, however, physicists and engineers need to be able to confirm that they are stored successfully without destroying them.

Physicists reveal how a lone spinon emerges in quantum magnetic models

Researchers from the Faculty of Physics at the University of Warsaw and the University of British Columbia have described how a so-called lone spinon—an exotic quantum excitation that is a single unpaired spin—can arise in magnetic models. The discovery deepens our understanding of the nature of magnetism and could have implications for the development of future technologies such as quantum computers and new magnetic materials. The work is published in Physical Review Letters.

Magnetism has been known to humanity since ancient times, when naturally magnetized magnetite was discovered. This finding soon found highly practical applications. The first compasses were created in the in China, and began to be used for navigation.

Today, magnets play an important role in many technologies that surround us, from computer memory and speakers to and medical diagnostics. Interestingly, alongside photography, magnets have also become a common souvenir of travel, occupying a prominent place in our homes.

Cracking the quantum code: Light and glass are set to transform computing

European researchers are developing quantum computers using light and glass, in a collaboration that promises breakthroughs in computing power, battery technology and scientific discovery.

Giulia Acconcia grew up in the picturesque, historic town of Spoleto, nestled in the foothills of Italy’s Apennine Mountains. Already in secondary school, she became fascinated with modern technology—a passion that would shape her future.

Her love of electronics led her to the Polytechnic University of Milan, Italy, where she now finds herself at the forefront of quantum computing research.

Individual defects in superconducting quantum circuits imaged for the first time

Individual defects in superconducting quantum circuits have been imaged for the first time, thanks to research by scientists at the National Physical Laboratory (NPL) in collaboration with Chalmers University of Technology and Royal Holloway University of London.

Light and heavy electrons cooperate in magic-angle superconductors

Electrons play many roles in solid materials. When they are weakly bound and able to travel—i.e., mobile—they can enable electrical conduction. When they are bound, or “heavy,” they can act as insulators. However, in certain solid materials, this behavior can be markedly different, raising questions about how these different types of electrons interact.

In a study just published in Nature Physics, researchers working with Professor of Physics and Applied Physics Amir Yacoby at Harvard examined the interplay between both types of electrons in this material, shedding new on how they may help form novel quantum states.

“Before our work, people could only ask ‘What is the overall ground state?’” said Andrew T. Pierce, one of the paper’s lead authors. Pierce, currently a fellow at Cornell University, was a graduate student in Yacoby’s lab when they began to study this question. What wasn’t clear was the true nature of these different states and how the separate light and heavy electrons joined forces to form them.

Quantum enhancement discovery could improve medical technologies

Technologies such as biomedical imaging and spectroscopy could be enhanced by a discovery in research that involved several institutions, including the University of Glasgow. Scientists have found that two-photon processes, which have applications in the study of Alzheimer’s disease and other nervous system disorders, can be strengthened by quantum light at far higher levels than previously thought possible.

The processes normally require high-intensity light but this can cause samples to be damaged or bleached.

It was suggested many years ago—and has since been demonstrated—that entangled could overcome this limitation. However, it has been widely believed that this quantum enhancement only survives for very faint light, raising doubts about the usefulness of the approach.

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