Category Archives: Quantum Physics

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Northeastern researchers have made what they describe as a groundbreaking discovery in the field of quantum mechanics.

Wei-Chi Chiu, a postdoctoral researcher at Northeastern reporting to Arun Bansil, university distinguished professor of physics at Northeastern, tells Northeastern Global News that his team has published a novel study examining the nature of a specific class of subatomic particles, whose very existence has eluded quantum physicists for nearly a century.

Chiu and his colleagues propose a new theoretical framework to explain how these particles, called Weyl fermions, interact with each other in certain materials. The findings, published in Nature Communications earlier this month, look beyond the framework of Albert Einstein's theory of relativity to probe these mysterious particles, Chiu says.

Weyl fermions were first discovered in 2015 by a group of physicists at Northeastern and Princeton universities. The discovery capped off an 85-year search for the massless particle, considered a basic building block of other subatomic particles, since its existence was first theorized by physicist Hermann Weyl in 1929.

In June of 2015, Bansil and the team of researchers predicted that a specific crystalline material, called Tantalum arsenide (TaAs), would host Weyl fermions. Soon after, the researchers demonstrated in an experimental paper the presence of the particles in TaAs through photoemission spectroscopy.

The discovery prompted a surge of experimental and theoretical explorations of Weyl fermions in different materials for want of a mechanical explanation of how they actually behave in real-time.

"Weyl fermions are relativistic particles that had actually never been seen, or observed, until 2015," Chiu says. "Our main focus in this work is understanding how these kinds of quasiparticles are interacting, and what the mechanisms are behind these interactions."

The most significant part of the researchers' findings, he says, is that the new framework for these quantum-level interactions challenges the longstanding view of "causality" as existing in spacetime. In Einstein's theory of relativity, the traditional view of causalityor mere cause-and-effectis that it is "time-ordered," meaning it is established in relation to chronological time. Under this view, causality refers to the principle that an event can only be influenced by other events that occur within its past light cone, Chiu says.

"This means that if 'A' causes event 'B,' then event 'A' must occur before event 'B' in both space and time," he says. "The light cone forms the event horizon or the boundary in spacetime which distinguishes between events that are and are not causally connected."

In other words, no object or signal can travel faster than the speed of light. This principle is sometimes referred to as the causality principle in relativity. The concept of causality in relativity is important, Chiu says, because it sets fundamental limits on what can be observed and measured in the universe.

Instead of thinking about the behavior of Weyl fermions in terms of spacetime, Chiu and his associates say these causal interactions are better understood as a result of measurable changes in the "energy-momentum" space.

"Our study, for the first time, shows how key concepts of causality and the associated event horizon in spacetime can be carried over into the field of correlated Weyl materials, and thus unveils fundamental connections between condensed matter and high-energy physics," Chiu says.

The work, he says, "opens up opportunities for exploring new connections between the world of particles and the larger world we experience every day."

"This study reveals for the first time how the ideas of causality that are enshrined in Einstein's theory of relativityand lead to the concepts of 'light cones' and 'event horizons' that have become the stuff of movies and common sci-fi workscan be generalized and expanded into the world of quantum materials," Bansil says,

More information: Wei-Chi Chiu et al, Causal structure of interacting Weyl fermions in condensed matter systems, Nature Communications (2023). DOI: 10.1038/s41467-023-37931-w

Journal information: Nature Communications

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Researchers pull back the quantum curtain on 'Weyl fermions' - Phys.org

About the opportunity

The University of Sydney's School of Physics are welcoming applicants for a Postdoctoral Research Associate in Quantum Optics, funded by Dr Sahand Mahmoodian's Australian Reserch Council grant, "Emergent many-body phenomena in engineered quantum optical systems". The field of research is quantum many-body physics of photons. The candidate can choose to undertake research on a range of topics within this area both focusing on fundamental research and for applications in developing quantum technologies.

Your key responsibilities will be to:

If you would like to find out more about the School of Physics leading research, click here

About you

The University values courage and creativity; openness and engagement; inclusion and diversity; and respect and integrity. As such, we see the importance of recruiting talent aligned to these values and are looking for a Postdoctoral Research Associate who has:

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Your employment is conditional upon the completion of all role required pre-employment or background checks in terms satisfactory to the University. Similarly, your ongoing employment is conditional upon the satisfactory maintenance of all relevant clearances and background check requirements. If you do not meet these conditions, the University may take any necessary step, including the termination of your employment.

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Postdoctoral Research Associate in Quantum Optics job with ... - Times Higher Education

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In physics, one often has to deal with different scales that can be described separately from one another: For the Earth's orbit around the sun, it makes absolutely no difference whether an elephant in the zoo walks to the left or to the right. And the movement of the elephant can be described without having to know anything about the properties of the electrons in its ear. The world can be divided into different scales.

In materials research, too, it is important to describe the behavior of particles on the appropriate scales. However, you first have to find out which scales are the decisive onesa difficult task for which there was previously no clear solution strategy. One could only hope to guess the solution with a lot of experience.

However, a mathematical method has now been found by an international research cooperation with the participation of the TU Wien and Saitama University in Japan to calculate the appropriate scalesan important step in the search for better materials for different areas of application, from microchips to photovoltaics. The method has now been published in the journal Physical Review X.

"In materials physics, electrons often cannot be viewed separately from one another," says Anna Kauch, who heads an FWF research project on this topic. "Particularly exciting phenomena such as magnetism or superconductivity can only be understood if many particles and their complex interactions are described together."

However, this is usually not possible with complete accuracy: If many particles are involved, then the formulas of quantum theory quickly become so big and so complex that even the best supercomputers in the world cannot solve them exactlynot even the state of the particles can then be written down exactly, because that would require more storage space than we will ever have available.

One must therefore look for certain approximations. These approximations often consist in being able to disregard certain size scales in certain cases. "Sometimes you can find quite simple physical arguments for it," says Markus Wallerberger, one of the authors of the paper. "A typical example of this are electrons and atomic nuclei in a crystal: the electrons are very light and move quickly. The atoms are much heavier, so on the time scale used to describe the motion of the electrons, the atoms can be considered rigid and immobile.

"In this case, we have split a complicated problem into two much simpler problems: we can now think about the fast movement of the electrons on the one hand and the much slower movement of the atoms on the otherand think about how the two are related." (a) QTT representation in momentum space. The rightmost bits (indices) represent fine structures in momentum space. Low entanglement structures are assumed between different length scales. (b) Schematic illustration of the bond dimensions along the chain representing the momentum dependence. The dashed line indicates the maximum bond dimensions in maximally entangled cases. (c) Fourier transform from momentum space to real space by applying a MPO. The orange diamonds represent the MPO tensors. Credit: Physical Review X (2023). DOI: 10.1103/PhysRevX.13.021015

But what do you do if you cannot see such an intuitive solution? So far, one could only guess in this case. But now it has been possible to develop a mathematical recipe for this situation. "In our paper, we show how to break down the complete description of such a system into different scales," explains Hiroshi Shinaoka, professor at Saitama University in Japan and leader of the study.

"It then automatically shows which scales are important and which ones can be left out. At the same time, the calculation method also tells us what the coupling between the different scales looks like and how we can then use it for further calculations."

More information: Hiroshi Shinaoka et al, Multiscale Space-Time Ansatz for Correlation Functions of Quantum Systems Based on Quantics Tensor Trains, Physical Review X (2023). DOI: 10.1103/PhysRevX.13.021015

Journal information: Physical Review X

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Scale separation: Breaking down unsolvable problems into solvable ones - Phys.org

Australian Industry and Science Minister Ed Husic. Source: AAP Image/Lukas Coch

Ahead of next weeks budget, the federal government has unveiled its inaugural national quantum strategy. The initiative was announced by Ed Husic, Minister for Industry and Science, on Wednesday.

While Australia has been involved in research into quantum technology for decades, this is the first time that a government strategy has been put in place to support the existing leadership in the space.

This will be a part of the Labor governments National Reconstruction Fund, $1 billion of which was set aside for critical technologies such as quantum.

Quantum technology is a complex topic. But at its core it utilises quantum mechanics the physics of sub-atomic particles. These are the building blocks of nature. Quantum physics looks at and explains the world at this minute scale.

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The ability to study, isolate and control these particles allows for the creation of new technologies and ways for faster medicine development and security infrastructure.

Quantum computing in particular allows for problem solving that isnt possible with older technology.

The consultation and research process for the strategy was led by Australias Chief Scientist, Dr Cathy Foley, with guidance from the National Quantum Advisory Committee.

The aim of the strategy is to utilise quantum technology to create new industries and boost jobs in the sector. According to the federal government, its estimated that quantum-based industries could create 19,400 direct jobs and $5.9 billion in revenue by 2045.

The strategy itself lists five priority areas:

I cant emphasise this enough, quantum technologies will be truly transformative. We are already seeing how quantum sensing equipment is making a huge difference for industry, Ed Husic said during his speech.

In time, quantum computing will unleash incredible computing power that can phenomenally outperform traditional computing.

By pairing a National Quantum Strategy with the National Reconstruction Fund were aiming to turn Australia into a global technology leader, building stronger industry and creating jobs for the future.

The Tech Council of Australia (TCA) which is the home of the Australian Quantum Alliance has welcomed the news.

We have strong foundations to build a globally successful quantum sector right here in Australia we are already home to more than 3% of global quantum startups and are attracting 3.6% of global venture capital investment, well above our 1.6% share of global GDP, TCA CEO, Kate Pounder, said in a statement.

While the announcement is a promising, and long-awaited start, it is just that. Q-CTRL is an Australian quantum computing startup that hopes to see more support and resources for the sector in the long term.

QCTRL is proud to be Australias first venture-capital-backed quantum technology company, one which has grown into a world leader in the industry. Were excited about our continued growth in Australia and our offices around the world, Q-CTRLs Head of government engagement, Charles Burnard, said in an email to SmartCompany.

As Minister Husic has made clear, the release of the Strategy today is the beginning of the journey, not the end. Realising the Strategys full potential will require the whole nations support, close cooperation and coordination at all levels of government, and sustained, meaningful backing for the sector

The TCA is also looking to the future on how to make this successful for Australia.

Our challenge is to now become a leader in commercialisation. Early commercialisation will deliver billions of dollars in economic value and thousands of jobs by 2030 globally and in Australia, while supporting our strategic and national security objectives, Pounder said.

Husic seems to agree with Burnards sentiments about a community and holistic approach to quantum.

Quantum, by its very nature, is a global endeavour. No one country can hope to corner the market, as it were, Husic said.

Only by working together can we unlock quantums full potential.

Continued here:

Australia's first quantum strategy predicts $6 billion in revenue and ... - SmartCompany

A University of Chicago study found links at the atomic level between photosynthesis and exciton condensatesa strange state of physics that allows energy to flow frictionlessly through a material. The finding is scientifically intriguing and may suggest new ways to think about designing electronics, the authors said.

University of Chicago scientists hope islands of exciton condensation may point way to new discoveries.

Scientists at the University of Chicago have found a connection between photosynthesis and exciton condensates, a state of physics that allows energy to flow without friction. This surprising finding, typically associated with materials well below room temperature, may inform future electronic design and help unravel complex atomic interactions.

Inside a lab, scientists marvel at a strange state that forms when they cool down atoms to nearly absolute zero. Outside their window, trees gather sunlight and turn them into new leaves. The two seem unrelatedbut a new study from the University of Chicago suggests that these processes arent so different as they might appear on the surface.

The study, published inPRX Energyon April 28, found links at the atomic level between photosynthesis and exciton condensatesa strange state of physics that allows energy to flow frictionlessly through a material. The finding is scientifically intriguing and may suggest new ways to think about designing electronics, the authors said.

As far as we know, these areas have never been connected before, so we found this very compelling and exciting, said study co-author Prof. David Mazziotti.

Mazziottis lab specializes in modelling the complicated interactions of atoms and molecules as they display interesting properties. Theres no way to see these interactions with the naked eye, so computer modeling can give scientists a window intowhythe behavior happensand can also provide a foundation for designing future technology.

In particular, Mazziotti and study co-authors Anna Schouten and LeeAnn Sager-Smith have been modelling what happens at the molecular level when photosynthesis occurs.

When a photon from the sun strikes a leaf, it sparks a change in a specially designed molecule. The energy knocks loose an electron. The electron, and the hole where it once was, can now travel around the leaf, carrying the energy of the sun to another area where it triggers a chemical reaction to make sugars for the plant.

Together, that traveling electron-and-hole-pair is referred to as an exciton. When the team took a birds-eye view and modeled how multiple excitons move around, they noticed something odd. They saw patterns in the paths of the excitons that looked remarkably familiar.

In fact, it looked very much like the behavior in a material that is known as a Bose-Einstein condensate, sometimes known as the fifth state of matter. In this material, excitons can link up into the same quantum statekind of like a set of bells all ringing perfectly in tune. This allows energy to move around the material with zero friction. (These sorts of strange behaviors intrigue scientists because they can be the seeds for remarkable technologyfor example, a similar state called superconductivity is the basis for MRI machines).

They saw patterns in the paths of the excitons that looked remarkably familiar.

According to the models created by Schouten, Sager-Smith and Mazziotti, the excitons in a leaf can sometimes link up in ways similar to exciton condensate behavior.

This was a huge surprise. Exciton condensates haveonlybeen seen when the material is cooled down significantly below room temperature. Itd be kind of like seeing ice cubes forming in a cup of hot coffee.

Photosynthetic light harvesting is taking place in a system that is at room temperature and whats more, its structure is disorderedvery unlike the pristine crystallized materials and cold temperatures that you use to make exciton condensates, explained Schouten.

This effect isnt totalits more akin to islands of condensates forming, the scientists said. But thats still enough to enhance energy transfer in the system, said Sager-Smith. In fact, their models suggest it can as much as double the efficiency.

This opens up some new possibilities for generating synthetic materials for future technology, Mazziotti said. A perfect ideal exciton condensate is sensitive and requires a lot of special conditions, but for realistic applications, its exciting to see something that boosts efficiency but can happen in ambient conditions.

Mazziotti said the finding also plays into a broader approach his team has been exploring for a decade.

The interactions between atoms and molecules in processes like photosynthesis are incredibly complexdifficult even for a supercomputer to handleso scientists have traditionally had to simplify their models in order to get a handle on them. But Mazziotti thinks some parts need to be left in: We think local correlation of electrons are essential to capturing how nature actually works.

The study was partially supported by the National Science Foundations QuBBE Quantum Leap Challenge Institute.

Reference: Exciton-Condensate-Like Amplification of Energy Transport in Light Harvesting by Anna O. Schouten, LeeAnn M. Sager-Smith and David A. Mazziotti, 28 April 2023, PRX Energy.DOI: 10.1103/PRXEnergy.2.023002

Funding: U.S. National Science Foundation, U.S. Department of Energy.

See more here:

Nature's Quantum Secret: Link Discovered Between Photosynthesis ... - SciTechDaily

image:from the Institute for Innate Immunity at the University Hospital Bonn. view more

Credit: Photo: Bruna Guerra Photography

Two researchers from the University of Bonn have been awarded a Proof of Concept Grant by the European Research Council (ERC) as part of a program designed to help researchers translate their ideas from previous ERC projects into commercial applications. Biologist Prof. Dr. Bernardo S. Franklin from the University Hospital Bonn and physicist Prof. Dr. Simon Stellmer will thus each receive 150,000 over a period of around one year.

Prof. Dr. Bernardo S. Franklin from the Institute for Innate Immunity and the ImmunoSensation2 Cluster of Excellence studies hematopoietic stem cells (HSCs), which develop into different blood cells through processes of cell division and differentiation. Bouts of inflammation that a person experiences as they get older will damage these stem cells, Bernardo S. Franklin says. Processes like this cause hyperactivation of the innate immune system in the elderly. This phenomenon, known as inflammaging, increases the risk of conditions including cardiovascular disease, diabetes and cancer, he adds.

Wiping the immune systems harmful memories of inflammation

The project that has now secured ERC funding, which is entitled Nanobodies to prevent hematopoietic stem cell bias and hyper-inflammation (UNBIAS), aims to return HSCs to their original state in order to wipe the immune systems harmful memories of inflammation. The researchers are using customized mini-antibodies known as nanobodies to achieve this. These antibodies, which are very small in relative terms, are taken from the blood of alpacas and can break up the places where inflammation develops.

Back in 2017, Franklin received a much-sought-after Starting Grant from the ERC worth some 1.5 million in funding. The Proof of Concept Grant will now build on this work already done. Our aim is to validate the use of nanobodies to combat inflammaging and license this technology or its applications for industrial partners, Franklin says. He believes that the project has the potential to alleviate the effects of inflammation and thus potentially save countless lives and the economic cost of illness.

Developing precise spinning sensors to measure the Earths rotation

Together with his team, Prof. Dr. Simon Stellmer from the Institute of Physics at the University of Bonn is studying how measuring devices that are already unbelievably accurate can keep on being improved and refined. In the GyroRevolution ERC project, for which they have now secured funding, they want to develop gyroscopes spinning sensors that are extremely precise. Specifically, gyroscopes are lasers with a ring-shaped trajectory that can be used to measure rotation. Geodesists use them to record the rotation of the Earth and detect earthquakes, for example. Even very tiny and extremely slow movements of structures or the soil can also be measured.

Stellmer and his team used technologies borrowed from quantum physics to develop their gyroscopes. High-stability lasers, optic resonators, frequency combs: originally developed for optical atomic clocks, the researchers tools now form the basis for creating improved gyroscopes. The working group is currently exploring several approaches and running several different designs of gyroscope, the largest of which measures 4 m by 4 m and is installed deep in the bowels of the Institute of Physics.

We want to build small yet sturdy spinning sensors that can be fitted inside buildings or sunk into holes, says Simon Stellmer, a member of the Matter and Light for Quantum Computing (ML4Q) Cluster of Excellence and the Matter Transdisciplinary Research Area at the University of Bonn. Earthquakes, climate change, crumbling bridges on the freewaythere are various ways these gyroscopes could be used, all of them highly relevant to society.

Even back when he was working on his ERC Starting Grant project, which secured its funding in 2017, Simon Stellmer was investigating precision measurements of this kind. In this project, he is addressing a very fundamental question: Why does the universe contain matter in the first place? His aim is to answer questions from the world of particle physics using the precision of quantum experiments rather than the high energy of large particle accelerators.

Two Proof of Concept proposals accepted

Were delighted that not one but two proposals from the University of Bonn for ERC Proof of Concept Grants have been accepted, says Sandra Speer, Head of the enaCom Transfer Center at the University of Bonn. The Transfer team at the Faculty of Medicine helped to submit the proposal to the ERC together with enaCom and Research Funding at the University of Bonn in what proved a highly successful collaboration.

Contact:

Prof. Dr. Bernardo S. FranklinInstitute for Innate ImmunityUniversity Hospital BonnPhone +49 228 28751981Email: franklin@uni-bonn.de

Prof. Dr. Simon StellmerInstitute of PhysicsUniversity of BonnPhone +49 228 733720Email: stellmer@uni-bonn.de

Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.

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Two ERC proof of concept grants for the University of Bonn - EurekAlert

In the publics mind, Stephen Hawking is a giant of 20th century science. He burst onto the popular stage with the 1988 publication of A Brief History of Time, which presented his esoteric ideas of evaporating black holes and the birth of the universe. It was an international bestseller, but given the complexity of its ideas, A Brief History has been called the most unread book of all time.

Hawking continued to explore the fundamental nature of the universe until his death in 2018. In a new book, On The Origin of Time, Belgian physicist Thomas Hertog unravels Hawkings final theory, which focuses upon one of the biggest questions of all just why our universe is the way it is.

Review: On the Origin of Time: Stephen Hawkings Final Theory Thomas Hertog (Penguin Random House)

Hertog is no passive player in this story, having been a student and collaborator of Hawking. He is, instead, an active participant. Intriguingly, as Hertog explains, we are all active participants in Hawkings final theory, shaping the universe by observing it.

In this new book, Hertog tells us that Hawkings final theory tries to address one of the deep mysteries of the universe, something known as the problem of cosmological fine-tuning.

Cosmologists have realised that the more they peer at the underlying nature of the universe (for instance the strengths of fundamental forces and the masses of fundamental particles), the more the cosmos seems tuned for our existence.

If the universe had been born with slightly different values for these fundamental properties, it would be dead and sterile, lacking the complexity and energy essential for life.

For some, the solution to cosmological fine-tuning lies in the multiverse, the idea that our universe is just one of countless others. Our universe, and all the others, crystallise out of a bout of eternal inflation, a super-energetic cosmic expansion. Each individual universe, at birth, is written with its own unique laws of physics. Most of these universes in the multiverse are dead, but our cosmic home won the physics lottery. We, unsurprisingly, find ourselves in a universe that can host life.

However, as Hertog writes in this new book, Hawking dismissed the multiverse and went on the hunt for an alternative solution to cosmic fine-tuning.

To get to this point, Hertog treads some very familiar ground, discussing the history of modern cosmological ideas. This includes the theoretical groundwork of Albert Einstein and Georges Lemaitre, and the observational insights of Edwin Hubble that revealed the expansion of the universe.

Hertog interweaves the story with the development, over the 20th century, of that other great pillar of physics, the strange behaviour in the world of the quantum, where the deterministic world of Isaac Newton, in which things have precise locations at precise times, is replaced by a fuzzy world of probabilities and uncertainties.

Usually we think of quantum mechanics describing the subatomic world, of electrons and atoms, but Hawking was thinking of the entire universe as a quantum system. The tale is brought up to date with the idea of cosmic inflation in the earliest instances of the universe and the surprising discovery of the dominance of dark energy in the closing years of the last century.Hawkings own story is similarly interwoven in the book including his revelation that black holes are not truly black.

Combining Einsteins general theory of relativity, which dictates the space-time curvature of a black hole, with quantum field theory, which describes the strange, ephemeral nature of seemingly empty space, Hawking showed that black holes actually radiate. Through this dribble of energy, black holes steadily evaporate into an eventual nothingness.

But if you are looking for an accurate description of just how Hawkings idea of black hole radiation operates, unfortunately Hertog relies on the same flawed picture of particles popping into existence at the edge of the hole as Hawking presented in A Brief History of Time. A copy of A Brief History of Time featuring a thumbprint of its author at an auction at Christies London in 2018. Neil Hall/AAP

Hertog also tells us that Hawking explored the state of the universe at the very beginning, arguing that at this initial point, at least in terms of general relativity, the density of stuff in the universe must have been infinite, (this idea is formally known as a singularity).

Hawking returned to this question with physicist Jim Hartle in the early 1980s to try and wrap quantum mechanics into the picture. Hartle and Hawking claimed that if you wind the universe back to the beginning, time loses its distinct nature and effectively becomes space. With this no boundary hypothesis, the universe did not have an origin, not at least one we would ever really understand.

Hawkings motivation for disliking the multiverse is a somewhat subtle argument, built on the idea of the anthropic principle, the fact that we should not be surprised to find ourselves in a universe which allows us to be here.

Hertog tells us that we should be, in some sense, typical of the possible observers who could inhabit the universes in the multiverse. But quite what typical means is a complicated topic. Does it mean that other life in other universes should be like life on Earth? Or typical in a more broader sense, that life should be composed of the same elements as us? Typical can be judged on many different criteria. And how will we ever find out how typical we are if we are forever limited to the observations of our one universe?

To posit an alternative solution, Hawkings first step was to upend the approach to understanding the universe.

The goal of modern science has been to unravel the fundamental operations of the universe and use these to predict how physical systems evolve. To do this, we need more than the laws of physics, but we need to know the starting point, the boundary conditions. But for a universe emerging from the strange singular state at its origin, where infinities abound, just what are these boundary conditions, and do they uniquely define the universe we inhabit?

Hertog explains that he and Hawking adopted a different view, a top-down view of the universe. Quantum mechanics is again wrapped into the picture, and the life of the universe is treated as a quantum system, described in terms of possibilities and probabilities.

It is here that Hugh Everett IIIs many-worlds interpretation of quantum mechanics makes its appearance. According to Everett, all of the possible outcomes of a quantum experiment play out in parallel existences, and it is this notion that Hawking applies to the universe.

Within this final theory, as expressed by Hertog, the observer now plays a central role. The fact that we all exist and observe the world around it, means we participate in shaping the universe we appear to inhabit.

Of all of the possible histories of the universe that could potentially exist in a sea of parallel universes, the fact that we are here observing this universe, singles out this universe, with all the others lost in a sea of quantum uncertainty. The situation becomes strangely self-referential.

At this point, the general reader is quite possibly going to be confused. This is, of course, quite a radical notion in understanding the nature of the universe. And, quite frankly, the reader might wonder what separates Hawkings final theory from what some might consider pseudo-scientific ramblings.

The idea that we, as observers, are essential for bringing the universe into being is not a new one, and is often the source of ridicule. Of course, given the scientific weight of the authors, this final theory must be given merit, but whether this hypothesis is a true contender for an accurate description of the life of our universe is hard to judge.

This should not put the reader off. Hertogs easy writing style jumps from topic to topic and provides an overview of the development of modern cosmology and the need for quantum mechanics in understanding the ultimate origins of the universe.

But when the going gets tough and the intricate ideas of Hawkings cosmos are explored, some things are stepped over a little too quickly and a little more time lingering on what might seem straightforward to quantum cosmologists would have been a benefit.

In closing, it is worth pointing out that there are some irritating features to the writing, including the almost hero worship Hawking receives. Clearly given the close relationship between the author and his subject, this is somewhat understandable, but can still be grating.

The text also mixes the philosophy-bashing that appears to be a badge of honour of modern physicists with various philosophical musings that underpin the cosmological and quantum thinking. But given the scope of the topic, and with a mix of anecdotes, quotes and analogies, Hertog provides an intriguing snapshot of our pondering of the ultimate origin of our universe.

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Stephen Hawking's final, god's-eye view of the cosmos ponders the ultimate origin of our universe - The Conversation

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Transporting energy is costly. When a current runs through conductive materials, some of the energy is lost due to resistance as particles within the material interactjust notice the warmth from your phone or laptop. This energy loss presents a hurdle to the advancement of many technologies and scientists are searching for ways to make superconductors that eliminate resistance.

Superconductors can also provide a platform for fault-tolerant quantum computing if endowed with topological properties. An example of the latter is the quantum Hall effect where the topology of electrons leads to universal, "quantized," resistance with accuracy up to one part in a billion, which finds uses in meteorology. Unfortunately, the quantum Hall effect requires extremely strong magnetic fields, typically detrimental to superconductivity. This makes the search for topological superconductors a challenging task.

In two new papers in Physical Review Letters and Physical Review B UConn Physicist Pavel Volkov and his colleagues propose how to experimentally manipulate the quantum particles, called quasiparticles, in very thin layers of ordinary superconductors to create topological superconductors by slightly twisting the stacked layers.

Volkov explains there is a lot of research being done on ways to engineer materials by stacking layers of two-dimensional materials together:

"Most famously, this has been done with graphene. Stacking two graphene layers in a particular way results in a lot of interesting new phenomena. Some parallel those in high-temperature superconductors, which was unexpected because, by itself, graphene is not superconducting."

Superconductivity happens when a material conducts current without any resistance or energy loss. Since resistance is a challenge for many technologies, superconducting materials have the potential to revolutionize how we do things, from energy transmission to quantum computing to more efficient MRI machines.

However, endowing superconductors with topological properties is challenging, says Volkov, and as of now, there are no materials that can reliably perform as topological superconductors.

The researchers theorize that there is an intricate relation between what happens inside the twisted superconductor layers and a current applied between them. Volkov says the application of a current makes the quasiparticles in the superconductor behave as if they were in a topological superconductor.

"The twist is essentially determining the properties, and funnily enough, it gives you some very unexpected properties. We thought about applying twisting to materials that have a peculiar form of superconductivity called nodal superconductivity," says Volkov.

"Fortunately for us, such superconductors exist and, for example, the cuprate high-temperature superconductors are nodal superconductors. What we claim is that if you apply a current between two twisted layers of such superconductors, it becomes a topological superconductor."

The proposal for current-induced topological superconductivity is, in principle, applicable at any twist angle, Volkov explains, and there is a wide range of angles that optimize the characteristics, which is unlike other materials studied so far.

"This is important because, for example, in twisted bilayer graphene, observation of interesting new phenomena requires to align the two layers to 1.1 degrees and deviations by .1 degrees are strongly detrimental. That means that one is required to make a lot of samples before finding one that works. For our proposal this problem won't be as bad. If you miss the angle even by a degree, it's not going to destroy the effect we predict."

Volkov expects that this topological superconductor has the potential to be better than anything else currently on the market. Though one caveat is they do not know exactly what the parameters of the resulting material will be, they have estimates that may be useful for proof of principle experiments.

The researchers also found unexpected behaviors for the special value of twist angle.

"We find a particular value of the angle, the so-called 'magic angle,' where a new state should appeara form of magnetism. Typically, magnetism and superconductivity are antagonistic phenomena but here, superconductivity begets magnetism, and this happens precisely because of the twisted structure of the layers." says Volkov.

Demonstrating these predictions experimentally will bring more challenges to overcome, including making the atoms-thick layers better themselves and determining the difficult-to-measure parameters, but Volkov says there is a lot of motivation behind developing these highly complex materials.

"Basically, the main problem so far is that the candidate materials are tricky to work with. There are several groups around the world trying to do this. Monolayers of nodal superconductors, necessary for our proposal have been realized, and experiments on twisted flakes are ongoing. Yet, the twisted bilayer of these materials has not yet been demonstrated. That's work for the future."

These materials hold promise for improving materials we use in everyday life, says Volkov. Things already in use that take advantage of the topological states include devices used to set resistance standards with high accuracy. Topological superconductors are also potentially useful in quantum computing, as they serve as a necessary ingredient for proposals of fault-tolerant qubits, the units of information in quantum computing. Volkov also emphasizes the promise topological materials hold for precision physics,

"Topological states are useful because they allow us to do precision measurements with materials. A topological superconductor may allow us to perform such measurements with unprecedented precision for spin (magnetic moment of electron) or thermal properties."

More information: Pavel A. Volkov et al, Current- and Field-Induced Topology in Twisted Nodal Superconductors, Physical Review Letters (2023). DOI: 10.1103/PhysRevLett.130.186001

Pavel A. Volkov et al, Magic angles and correlations in twisted nodal superconductors, Physical Review B (2023). DOI: 10.1103/PhysRevB.107.174506

Journal information: Physical Review Letters , Physical Review B

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The exciting possibilities of tiny, twisted superconductors - Phys.org

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by Ingrid Fadelli , Phys.org

When light strongly interacts with matter, it can produce unique quasi-particles called polaritons, which are half light and half matter. In recent decades, physicists explored the realization of polaritons in optical cavities and their value for the development of highly performing lasers or other technologies.

Researchers at University of Manitoba recently developed a highly performing device based on cavity magnon polaritons that can emit and amplify microwaves. This device, introduced in Physical Review Letters, was found to significantly outperform previously proposed solid-state devices for coherent microwave emission and amplification at room temperature.

"In 1992, Claude Weisbush, a French semiconductor physicist working in Japan, discovered cavity exciton polariton by confining light in a quantum microcavity to interact with semiconductors," Can-Ming Hu, the researcher who directed the study, told Phys.org.

"This led to the invention of polariton lasers with superior performance that have transformed solid-state laser technology. Two decades later, the magnetism community re-discovered cavity magnon polariton by confining microwaves in a cavity to interact with magnetic materials, such a half photon and half magnon quasi-particle was first discovered by Joe Artman and Peter Tannenwald in 1955 at MIT, which went largely unnoticed until recently."

Wireless communication and quantum information technologies require coherent on-chip microwave sources. Motivated by this need, Hu and his colleagues set out to explore the potential use of cavity magnon polaritons to achieve high-quality microwave emission and amplification.

"Intrigued by the resemblance between cavity magnon polariton and cavity exciton polariton, I became curious whether the cavity magnon polariton might help us to make better solid-state microwave sources," Hu said. "So, in 2015, my group launched a study to explore microwave emission of cavity magnon polaritons."

The researchers initially set out to create a lightmatter coupled system based on cavity magnon polaritons for coherent microwave emission. They ultimately hoped to achieve a higher performance than those reported in previous works, while retaining their device's stability and controllability as a hybrid lightmatter coupled system.

"First, we follow the principle proposed in 1920 by Dutch physicist van der Pol: using nonlinear damping to balance gain in an amplified oscillatory system, one can design and optimize a stable gain-driven cavity," Bimu Yao, an associate professor from the Chinese Academy of Sciences who carried out this study at the University of Manitoba, told Phys.org. "Then, we set a magnetic material into such a gain-driven microwave cavity, letting the amplified microwaves to strongly interact with magnons."

The strong interaction between amplified microwaves and magnons in the researchers' system produces a new type of polariton, which they dubbed a "gain-driven" polariton. Compared to conventional polaritons realized in previous studies, this gain-driven polariton has a stable phase, which in turn enables the coherent emission of microwave photons.

"For decades, the magnetism community has been working on spin-toque oscillator (STO), which is a solid-state device that utilizes magnons to produce coherent microwaves," Yongsheng Gui, a research associate at the University of Manitoba who carried out the study, told Phys.org. "The major hurdle is that the emission power of the STO is typically limited to less than 1 nW. Our device's output is a million times more powerful, and the emission quality factor is a thousand times better."

In initial evaluations, a proof-of-principle device created by this team of researchers achieved remarkable results, outperforming both STOs and solid-state masers developed in the past. Masers are devices that use the stimulated emission of radiation by atoms to amplify or generate microwave radiation.

"Outside of the magnetism community, there have been divers efforts for developing masers," Gui said. "Compared with the best solid-state maser, our device's output is a billion times more powerful, with a comparable emission quality factor."

The new gain-driven polariton realized by Hu and his colleagues could open exciting new possibilities for the development of highly performing solid-state microwave sources that can be integrated on-chip. In addition to their compact sizes, these polariton microwave sources are frequency tunable due to the fabulous controllability of light-matter interaction. They could ultimately be integrated in a broad range of technologies and devices, including wireless communication systems and quantum computers.

"As the physics of gain-driven light-matter interaction is new, our study may also lead to new discoveries beyond microwave applications," Hu added. "We have now submitted a patent application, and my students are working on developing prototype devices together with industry partners."

More information: Bimu Yao et al, Coherent Microwave Emission of Gain-Driven Polaritons, Physical Review Letters (2023). DOI: 10.1103/PhysRevLett.130.146702

Can-Ming Hu, Dawn of Cavity Spintronics, arXiv (2015). DOI: 10.48550/arxiv.1508.01966

Journal information: Physical Review Letters , arXiv

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A highly performing device for polariton-based coherent microwave emission and amplification - Phys.org

Newswise NEWPORT NEWS, VA Experts in high-performance computing and data management are gathering in Norfolk next week for the 26th International Conference on Computing in High Energy and Nuclear Physics (CHEP2023). Held approximately every 18 months, this high-impact conference will be held at the Norfolk Marriott Waterside in Norfolk, Va., May 8-12. CHEP2023 is hosted by the U.S. Department of Energys Thomas Jefferson National Accelerator Facility in nearby Newport News, Va. This is the first in-person CHEP conference to be held since 2019.

Science is driven by data. As research has progressed, so has the sheer volume of scientific data. The CHEP2023 conference will host more than 500 top computational scientists, data scientists, experimentalists and data center managers as they address the computing, networking and software issues for the worlds leading dataintensive science experiments.

Conference attendees will be welcomed to Virginia by Representative Robert C. Bobby Scott (VA-03), who represents the congressional district that includes Jefferson Lab and the conference venue. Old Dominion University Dean of the College of Sciences and Professor of Physics Gail Dodge, Jefferson Lab Director Stuart Henderson, and Jefferson Lab Associate Director of the Computational Sciences and Technology Division and Chief Information Officer Amber Boehnlein will also welcome attendees to these discussions at the intersection of physics and computing.

The CHEP conferences highlight key trends, challenges and solutions in computing as it applies to research in nuclear and high energy physics. This edition of the conference will place special emphasis on high-performance data organization, management and access, a topic of interest and relevance throughout the scientific community.

CHEP2023 features twelve parallel session tracks, where attendees will discuss such topics as: online and offline computing, data organization, software engineering, analysis tools, AI & machine learning, exascale science and quantum computing. The conference will also feature a special workforce development roundtable with speakers who are building an equitable STEM workforce for the future through mentorship programs that promote STEM education for students of all levels.

The CHEP conference location rotates among the Americas, Asia and Europe. It is typically held every 18 months. This is the first in-person CHEP conference to be held since 2019.

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Jefferson Science Associates, LLC, manages and operates the Thomas Jefferson National Accelerator Facility, or Jefferson Lab, for the U.S. Department of Energy's Office of Science. JSA is a wholly owned subsidiary of the Southeastern Universities Research Association, Inc. (SURA).

DOEs Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, visit https://energy.gov/science.

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Jefferson Lab Hosts International Computing in High Energy and Nuclear Physics Conference - Newswise