Physics News and Discussions

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Experiments reveal formation of a new state of matter: Electron quadruplets
https://phys.org/news/2021-10-reveal-fo ... plets.html
by KTH Royal Institute of Technology

The central principle of superconductivity is that electrons form pairs. But can they also condense into foursomes? Recent findings have suggested they can, and a physicist at KTH Royal Institute of Technology today published the first experimental evidence of this quadrupling effect and the mechanism by which this state of matter occurs.

Reporting today in Nature Physics, Professor Egor Babaev and collaborators presented evidence of fermion quadrupling in a series of experimental measurements on the iron-based material, Ba1−xKxFe2As2. The results follow nearly 20 years after Babaev first predicted this kind of phenomenon, and eight years after he published a paper predicting that it could occur in the material.

The pairing of electrons enables the quantum state of superconductivity, a zero-resistance state of conductivity which is used in MRI scanners and quantum computing. It occurs within a material as a result of two electrons bonding rather than repelling each other, as they would in a vacuum. The phenomenon was first described in a theory by, Leon Cooper, John Bardeen and John Schrieffer, whose work was awarded the Nobel Prize in 1972.

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Physicists announce results that boost evidence for new fundamental physics

by University of Cambridge
https://phys.org/news/2021-10-physicist ... ental.html

Results announced by the LHCb experiment at CERN have revealed further hints for phenomena that cannot be explained by our current theory of fundamental physics.

In March 2020, the same experiment released evidence of particles breaking one of the core principles of the Standard Model—our best theory of particles and forces—suggesting the possible existence of new fundamental particles and forces.

Now, further measurements by physicists at Cambridge's Cavendish Laboratory have found similar effects, boosting the case for new physics.

The Standard Model describes all the known particles that make up the universe and the forces that they interact through. It has passed every experimental test to date, and yet physicists know it must be incomplete. It does not include the force of gravity, nor can it account for how matter was produced during the Big Bang, and contains no particle that could explain the mysterious dark matter that astronomy tells us is five times more abundant than the stuff that makes up the visible world around us.

As a result, physicists have long been hunting for signs of physics beyond the Standard Model that might help us to address some of these mysteries.

One of the best ways to search for new particles and forces is to study particles known as beauty quarks. These are exotic cousins of the up and down quarks that make up the nucleus of every atom.

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New photonic chip for isolating light may be key to miniaturizing quantum devices
https://phys.org/news/2021-10-photonic- ... izing.html
by University of Illinois at Urbana-Champaign

Light offers an irreplaceable way to interact with our universe. It can travel across galactic distances and collide with our atmosphere, creating a shower of particles that tell a story of past astronomical events. Here on earth, controlling light lets us send data from one side of the planet to the other.

Given its broad utility, it's no surprise that light plays a critical role in enabling 21st century quantum information applications. For example, scientists use laser light to precisely control atoms, turning them into ultra-sensitive measures of time, acceleration, and even gravity. Currently, such early quantum technology is limited by size—state-of-the-art systems would not fit on a dining room table, let alone a chip. For practical use, scientists and engineers need to miniaturize quantum devices, which requires re-thinking certain components for harnessing light.

Now IQUIST member Gaurav Bahl and his research group have designed a simple, compact photonic circuit that uses sound waves to rein in light. The new study, published in the October 21 issue of the journal Nature Photonics, demonstrates a powerful way to isolate, or control the directionality of light. The team's measurements show that their approach to isolation currently outperforms all previous on-chip alternatives and is optimized for compatibility with atom-based sensors.

"Atoms are the perfect references anywhere in nature and provide a basis for many quantum applications," said Bahl, a professor in Mechanical Science and Engineering (MechSe) at the University of Illinois at Urbana-Champaign. "The lasers that we use to control atoms need isolators that block undesirable reflections. But so far the isolators that work well in large-scale experiments have proved tough to miniaturize."

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'Raindrops on the roof-technique' reveals new quantum liquid
https://phys.org/news/2021-10-raindrops ... iquid.html
by Bruno Van Wayenburg, Leiden Institute of Physics

Koen Bastiaans and his colleagues have discovered a new quantum liquid unlike anything ever seen. They did it by using a technique that can be compared to listening to the sound of raindrops falling on a roof.

Perhaps you still remember those old-fashioned light bulbs; they gave a cozy glow, they got hot, and nowadays they would greatly increase your electricity bill. Why? They were made out of a material with a large electrical resistance. All materials have a certain resistance to conducting electricity.

All materials? Yes, except for a special class of materials called superconductors. These transport electricity without any resistance when they are cooled below certain (extremely low) temperatures. How they work is one of the enduring mysteries of physics.

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Researchers develop a new way to control and measure energy levels in a diamond crystal
https://phys.org/news/2021-10-energy-di ... ystal.html
by Massachusetts Institute of Technology

Physicists and engineers have long been interested in creating new forms of matter, those not typically found in nature. Such materials might find use someday in, for example, novel computer chips. Beyond applications, they also reveal elusive insights about the fundamental workings of the universe. Recent work at MIT both created and characterized new quantum systems demonstrating dynamical symmetry—particular kinds of behavior that repeat periodically, like a shape folded and reflected through time.

"There are two problems we needed to solve," says Changhao Li, a graduate student in the lab of Paola Cappellaro, a professor of nuclear science and engineering. Li published the work recently in Physical Review Letters, together with Cappellaro and fellow graduate student Guoqing Wang. "The first problem was that we needed to engineer such a system. And second, how do we characterize it? How do we observe this symmetry?"

Concretely, the quantum system consisted of a diamond crystal about a millimeter across. The crystal contains many imperfections caused by a nitrogen atom next to a gap in the lattice—a so-called nitrogen-vacancy center. Just like an electron, each center has a quantum property called a spin, with two discrete energy levels. Because the system is a quantum system, the spins can be found not only in one of the levels, but also in a combination of both energy levels, like Schrodinger's theoretical cat, which can be both alive and dead at the same time.

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Physicists discover how particles self-assemble
https://phys.org/news/2021-11-physicist ... emble.html
by New York University

A team of physicists has discovered how DNA molecules self-organize into adhesive patches between particles in response to assembly instructions. Its findings offer a "proof of concept" for an innovative way to produce materials with a well-defined connectivity between the particles.

The work is reported in Proceedings of the National Academy of Sciences.

"We show that one can program particles to make tailored structures with customized properties," explains Jasna Brujic, a professor in New York University's Department of Physics and one of the researchers. "While cranes, drills, and hammers must be controlled by humans in constructing buildings, this work reveals how one can use physics to make smart materials that 'know' how to assemble themselves."

Scientists have long sought a means for molecules to self-assemble and have achieved breakthroughs on many fronts. However, less developed are measures in which these tiny particles self-assemble with a preprogrammed number of bonds.

To address this, Brujic and her colleagues, Angus McMullen, a postdoctoral researcher in NYU's Department of Physics, and Sascha Hilgenfeldt, a professor of mechanical science and engineering at the University of Illinois, Urbana-Champaign, ran a series of experiments to capture—and manipulate—the behavior of DNA molecules on particle surfaces.

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Fundamental Quantum Theorem Applies to Temperatures Beyond Absolute Zero
November 11, 2021 by Brian Wang
https://www.nextbigfuture.com/2021/11/173732.html

The adiabatic theorem – a fundamental achievement of quantum mechanics – was first formulated by Max Born and Vladimir Fock at the dawn of quantum mechanics. The theorem ensures that the evolving quantum state always remains close the so-called instantaneous eigenstate if external parameters change slowly enough. In a sense, adiabatic evolution is something like taking a class of first-graders on a tour of a museum: you should lead your class carefully and without haste to make sure that by the end of the tour no one’s missing and all the exhibits are intact.

Above – A quantum spin is moved around a wire along a circular trajectory. Electrons in the wire are magnetically coupled to the spin due to fluctuations of the current. The many-body adiabaticity of the electron-spin system at finite temperature is robust with respect to increasing the length of the wire. In contract, the pure state adiabaticity breaks down at any finite driving rate.

Although the adiabatic theorem has been refined and improved since Born and Fock’s time, its major limitation was that it worked only for the so called pure states but not all quantum states. This means that it could be applied to systems at absolute zero only but never at finite temperatures. In our museum example, the tour could go off without a hitch only if the class consisted of well-behaved straight-A pupils, which is hardly possible in real life. Just as there can be no class without naughty kids, there can be no strictly zero temperature.

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Quantum confinement discovered in porous nano-photocatalyst
https://phys.org/news/2021-11-quantum-c ... alyst.html
by City University of Hong Kong

The City University of Hong Kong research team used this photocatalytic reactor to do experiments on the hydrogen-producing photocatalyst. Credit: City University of Hong Kong

Green hydrogen production from solar water splitting has attracted a great deal of interest in recent years because hydrogen is a fuel of high energy density. A research team co-led by scholars from City University of Hong Kong (CityU) and Germany discovered the quantum confinement effect in a photocatalyst of a 3D-ordered macroporous structure. The quantum confinement effect was found to enable hydrogen production under visible light. The findings offer an option for addressing energy and environmental challenges.

The research was co-led by Dr. Ng Yun Hau, Associate Professor in CityU's School of Energy and Environment (SEE), and researchers from Germany. Their findings were published in the scientific journal ACS Energy Letters, titled "Unveiling Carrier Dynamics in Periodic Porous BiVO4 Photocatalyst for Enhanced Solar Water Splitting."

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A computer algorithm that speeds up experiments on plasma
https://phys.org/news/2021-11-algorithm-plasma.html
by Bob Yirka , Phys.org

A team of researchers from Tri Alpha Energy Inc. and Google has developed an algorithm that can be used to speed up experiments conducted with plasma. In their paper published in the journal Scientific Reports, the group describes how they plan to use the algorithm in nuclear fusion research.

As research into harnessing nuclear fusion has progressed, scientists have found that some of its characteristics are too complex to be solved in a reasonable amount of time using current technology. So they have increasingly turned to computers to help. More specifically, they want to adjust certain parameters in a device created to achieve fusion in a reasonable way. Such a device, most in the field agree, must involve the creation of a certain type of plasma that is not too hot or too cold, is stable, and has a certain desired density.

Finding the right parameters that meet these conditions has involved an incredible amount of trial and error. In this new effort, the researchers sought to reduce the workload by using a computer to reduce some of the needed trials. To that end, they have created what they call the "optometrist's algorithm." In its most basic sense, it works like an optometrist attempting to measure the visual ability of a patient by showing them images and asking if they are better or worse than other images. The idea is to use the crunching power of a computer with the intelligence of a human being—the computer generates the options and the human tells it whether a given option is better or worse.

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Scientists Observe Quantum Spin Liquids: A State of Matter We've Never Seen Before
DAVID NIELD
7 DECEMBER 2021

An exotic and totally new state of matter called a quantum spin liquid has been hypothesized for decades, and now scientists have been able to observe it in a laboratory for the first time.

The 'liquid' part refers to electrons that are constantly changing and fluctuating inside a magnetic material at low temperatures. Unlike regular magnets, in this case the electrons don't stabilize or settle into the structured lattice of a solid as they are cooled.

The 'quantum spin' refers to orientation of angular momentum (up or down) carried by particles, which are entangled in pairs with opposing spins. Now that the state has been observed for the first time, it's hoped that the discovery can advance progress in the development of quantum computers.

"It is a very special moment in the field," says quantum physicist Mikhail Lukin, from Harvard University in Massachusetts. "You can really touch, poke, and prod at this exotic state and manipulate it to understand its properties... it's a new state of matter that people have never been able to observe."

https://www.sciencealert.com/scientists ... GZmYSqPps8

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Physicists discover special transverse sound wave
https://phys.org/news/2021-12-physicist ... verse.html
by City University of Hong Kong

Can you imagine sound traveling in the same way as light does? A research team at City University of Hong Kong (CityU) has discovered a new type of sound wave: The airborne sound wave vibrates transversely and carries both spin and orbital angular momentum like light does. The findings shattered scientists' previous beliefs about the sound wave, opening an avenue to the development of novel applications in acoustic communications, acoustic sensing and imaging.

The research was initiated and co-led by Dr. Shubo Wang, Assistant Professor in the Department of Physics at CityU, and conducted in collaboration with scientists from Hong Kong Baptist University (HKBU) and the Hong Kong University of Science and Technology (HKUST). It was published in Nature Communications, titled "Spin-orbit interactions of transverse sound."

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Toward achieving megatesla magnetic fields in the laboratory

by Osaka University
https://phys.org/news/2021-12-megatesla ... atory.html

Recently, a research team at Osaka University has successfully demonstrated the generation of megatesla (MT)-order magnetic fields via three-dimensional particle simulations on laser-matter interaction. The strength of MT magnetic fields is 1–10 billion times stronger than geomagnetism (0.3–0.5 G), and these fields are expected to be observed only in the close vicinity of celestial bodies such as neutron stars or black holes. This result should facilitate an ambitious experiment to achieve MT-order magnetic fields in the laboratory, which is now in progress.

Since the 19th century, scientists have strived to achieve the highest magnetic fields in the laboratory. To date, the highest magnetic field observed in the laboratory is in the kilotesla (kT)-order. In 2020, Masakatsu Murakami at Osaka University proposed a novel scheme called microtube implosions (MTI) to generate ultrahigh magnetic fields on the MT-order. Irradiating a micron-sized hollow cylinder with ultraintense and ultrashort laser pulses generates hot electrons with velocities close to the speed of light. Those hot electrons launch a cylindrically symmetric implosion of the inner wall ions towards the central axis. An applied pre-seeded magnetic field of the kilotesla-order, parallel to the central axis, bends the trajectories of ions and electrons in opposite directions because of the Lorentz force. Near the target axis, those bent trajectories of ions and electrons collectively form a strong spin current that generates MT-order magnetic fields.

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Towards quantum states of sound
https://phys.org/news/2021-12-quantum-states.html
by Hayley Dunning, Imperial College London

Researchers make key steps towards generating quantum states of sound inside a microscopic device using laser light and single-photon measurements.

Across the globe, researchers can now generate and control quantum states in a wide variety of different physical systems spanning individual particles of light to complex molecules comprising thousands of atoms. This control is enabling powerful new quantum technologies to be developed, such as quantum computing and quantum communications, and also offers exciting paths to test the foundations of quantum physics. In particular, a key current challenge is how to create quantum states on a larger scale, which will enable the technological potential of quantum physics to be established and the boundary of quantum physics to be explored.

A team of researchers at Imperial College London, together with the University of Oxford, the Niels Bohr Institute, the Max Planck Institute for the Science of Light, and Australian National University have generated and observed non-Gaussian states of high-frequency sound waves comprising more than a trillion atoms. More specifically, the team transform a randomly fluctuating sound field in thermal equilibrium to a pattern thrumming with a more specific magnitude.

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Exotic six-quark particle predicted by supercomputers
https://phys.org/news/2021-12-exotic-si ... uters.html
by RIKEN

The predicted existence of an exotic particle made up of six elementary particles known as quarks by RIKEN researchers could deepen our understanding of how quarks combine to form the nuclei of atoms.

Quarks are the fundamental building blocks of matter. The nuclei of atoms consist of protons and neutrons, which are in turn made up of three quarks each. Particles consisting of three quarks are collectively known as baryons.

Scientists have long pondered the existence of systems containing two baryons, which are known as dibaryons. Only one dibaryon exists in nature—deuteron, a hydrogen nucleus made up of a proton and a neutron that are very lightly bound to each other. Glimpses of other dibaryons have been caught in nuclear-physics experiments, but they had very fleeting existences.

"Although the deuteron is the only known stable dibaryon, many more dibaryons may exist," says Takuya Sugiura of the RIKEN Interdisciplinary Theoretical and Mathematical Sciences Program. "It's important to study which pairs of baryons form dibaryons and which do not because this provides valuable insights into how quarks form matter."

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Einstein's theory passes rigorous 16-year tests
https://phys.org/news/2021-12-einstein- ... -year.html
by CSIRO

An international team has used telescopes around the world, including CSIRO's Parkes radio telescope—Murriyang, to complete the most challenging tests yet of Einstein's general theory of relativity.

The team, led by Professor Michael Kramer from the Max-Planck-Institute for Radio Astronomy in Bonn, Germany, showed that Einstein's theory published in 1915 still holds true.

Dr. Dick Manchester, a Fellow at Australia's national science agency, CSIRO, and a member of the research team, explained how this result provides us with a more precise understanding of our Universe.

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Gravitational wave scientists set their sights on dark matter
https://phys.org/news/2021-12-gravitati ... -dark.html
by Cardiff University

The technologies behind one of the biggest scientific breakthroughs of the century—the detection of gravitational waves—are now being used in the long-standing search for dark matter.

Thought to make up roughly 85 percent of all matter in the universe, dark matter has never been observed directly and remains one of the biggest unsolved mysteries in modern physics.

With extremely sensitive detectors now at their disposal, already proven through several outstanding discoveries, scientists believe that existing gravitational wave technology has the true potential to finally discover the exotic material and even find out what it is made of.

In a study published today in Nature, a team led by scientists from Cardiff University's Gravity Exploration Institute has taken the first step towards this goal by using the instruments, known as laser interferometers, to look for a new kind of dark matter for the very first time.

Until recently, it was widely believed that dark matter was composed of heavy elementary particles.

[Yuli Ban]

Tardigrade is first multicellular organism to be quantum entangled

A tardigrade has been quantum entangled with a superconducting qubit – and lived to tell the tale. It is the first time a multicellular organism has been placed in this strange quantum state and raises questions about what it means for living things to be entangled.

Tardigrades are microscopic animals that can survive extreme temperatures and pressures in a hibernating state called a tun. Rainer Dumke and his colleagues at Nanyang Technological University, Singapore, placed one of these hibernating tardigrades on a superconducting qubit

https://arxiv.org/abs/2112.07978

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Researchers use electron microscope to turn nanotube into tiny transistor
https://phys.org/news/2021-12-electron- ... istor.html
by Queensland University of Technology

An international team of researchers have used a unique tool inserted into an electron microscope to create a transistor that's 25,000 times smaller than the width of a human hair.

The research, published in the journal Science, involves researchers from Japan, China, Russia and Australia who have worked on the project that began five years ago.

QUT Center for Materials Science co-director Professor Dmitri Golberg, who led the research project, said the result was a "very interesting fundamental discovery" which could lead a way for the future development of tiny transistors for future generations of advanced computing devices.

"In this work, we have shown it is possible to control the electronic properties of an individual carbon nanotube," Professor Golberg said.

The researchers created the tiny transistor by simultaneously applying a force and low voltage which heated a carbon nanotube made up of few layers until outer tube shells separate, leaving just a single-layer nanotube.

The heat and strain then changed the "chilarity" of the nanotube, meaning the pattern in which the carbon atoms joined together to form the single-atomic layer of the nanotube wall was rearranged.

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Could an Overlooked Quantum Theory Help The Universe Make Sense Again?

https://www.sciencealert.com/pilot-waves

Introduction:

(Science Alert) Back in the 1920s, when the field of quantum physics was still in its infancy, a French scientist named Louis de Broglie had an intriguing idea.

In response to confusion over whether light and matter were fundamentally particles or waves, he suggested an alternative: what if both were true? What if the paths taken by quantum objects were guided by something that rose and fell like an ocean swell?

His hypothesis was the foundation of what would later become pilot wave theory, but it wasn't without its problems. So, like any beautiful idea that falters in the face of experiment, it swiftly became a relic of scientific history.

Today, the majority of physicists subscribe to what's referred to as the 'Copenhagen interpretation of quantum mechanics', which, generally speaking, doesn't give precise locations and momentums to particles until they're measured, and therefore observed.

Pilot wave theory, on the other hand, suggests that particles do have precise positions at all times, but in order for this to be the case, the world must also be strange in other ways – which led to many physicists dismissing the idea.

[Yuli Ban]