Physics News and Discussions

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Scientists Build Working Particle Accelerator the Size of a Coin
It's 54 million times smaller than the Large Hadron Collider.
By Ryan Whitwam October 27, 2023

The Large Hadron Collider (LHC) continues to amaze and delight scientists as it teases apart the most intricate natural phenomena in the universe. It's just so big, though. Researchers have successfully activated a tiny particle accelerator that's not even pocket-sized—it could get lost in your pocket. The nanophotonic electron accelerator (NEA) is the size of a small coin, but it could have a big impact.

The nanophotonic electron accelerator is a microchip just a few millimeters across, designed by scientists at Germany's Friedrich–Alexander University of Erlangen–Nuremberg (FAU). Inside is an even more minuscule vacuum tube, inside which are thousands of microscopic pillars. The chip is designed to accelerate electrons, which are negatively charged, by firing short laser pulses at the pillars. This technology was proposed in 2015, but this is the first time one has been tested.

https://www.extremetech.com/science/sci ... -of-a-coin

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Physicists trap electrons in a 3D crystal for the first time
https://phys.org/news/2023-11-physicist ... ystal.html
by Massachusetts Institute of Technology

Electrons move through a conducting material like commuters at the height of Manhattan rush hour. The charged particles may jostle and bump against each other, but for the most part, they're unconcerned with other electrons as they hurtle forward, each with their own energy.

But when a material's electrons are trapped together, they can settle into the same energy state and behave as one. In physics, this collective, zombie-like state is known as an electronic "flat band." Scientists predict that when electrons are in this state, they can start to feel the quantum effects of other electrons and act in coordinated, quantum ways. Then, exotic behavior such as superconductivity and unique forms of magnetism may emerge.

Now, physicists at MIT have successfully trapped electrons in a pure crystal. It is the first time scientists have achieved an electronic flat band in a three-dimensional material. With some chemical manipulation, the researchers also showed they could transform the crystal into a superconductor—a material that conducts electricity with zero resistance.

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Dynamics of skyrmion spin states confirmed in neutron-scattering experiments
https://phys.org/news/2023-11-dynamics- ... ering.html
by RIKEN

RIKEN researchers have brought low-energy devices based on spintronics one step closer, by measuring the dynamics of tiny magnetic vortices.

At present, all our information technologies are based on conventional electronics, which involves shunting electric charge around circuits. However, electrons have another property known as spin, which could be exploited to make faster and more efficient devices.

Hazuki Kawano-Furukawa of the RIKEN Center for Emergent Matter Science and her co-workers are leading efforts to develop this field of spintronics. In particular, they are exploring the use of nanoscale magnetic whirlpools called skyrmions.

"Skyrmions can be controlled with significantly smaller currents or electric fields," explains Kawano-Furukawa. "This makes them highly promising for future applications in information and communication technologies, such as computer memory that doesn't need power to keep stored data."

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Pioneering robot arm poised to reach new heights in quantum
https://phys.org/news/2023-11-robot-arm ... antum.html
by University of Bristol

Scientists carrying out quantum research will be able to do so faster and more adaptably, thanks to a new robotic arm which could hold the key to major breakthroughs.

The invention, developed by researchers in Quantum Engineering Technology Labs and the Bristol Robotics Laboratory (BRL) at the University of Bristol, has a unique design, allowing quantum experiments to be conducted with unprecedented levels of speed, detail and complexity.

Quantum technology has a host of potential real-world applications, from health advances in monitoring the condition of cells to communication in space.

Experiments in quantum often require highly constrained environments, sometimes combining ultra-low temperatures, atomic-scale interactions, and tightly-aligned laser beams.

By building robotic features into quantum experiments, scientists will now be able to investigate these experiments with increased prototyping speed, control, and robustness.

The research findings and robotic arm were presented in the journal Advanced Science.

Lead author Dr. Joe Smith, Senior Research Associate in the School of Electrical, Electronic and Mechanical Engineering at the University of Bristol said, "We couldn't have performed this experiment using standard lab components, so we decided to look into robotics. We've shown that robotic arms are mature enough to navigate very complex settings."

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An anomalous relativistic emission arising from the intense interaction of lasers with plasma mirrors
https://phys.org/news/2023-11-anomalous ... ction.html
by Ingrid Fadelli , Phys.org

Interactions between intense laser pulses and plasma mirrors have been the focus of several recent physics studies due to the interesting effects they produce. Experiments have revealed that these interactions can generate a non-linear physical process known as high-order harmonics, characterized by the emission of extreme ultraviolet radiation (XUV) and brief flashes of laser light (i.e., attosecond pulses).

Researchers at The Extreme Light Infrastructure ERIC in Czechia and Osaka University in Japan recently uncovered a surprising transition that takes place during interactions between intense laser pulses and plasma mirrors. This transition, marked by an anomalous emission of coherent XUV radiation, was outlined in a paper published in Physical Review Letters.

"Relativistic oscillating mirrors are a fascinating concept with great potential for intense attosecond pulse and bright XUV generation," Marcel Lamač, one of the researchers who carried out the study, told Phys.org.

"We were reinvestigating some of the assumptions held in previous works and found that strong self-modulation can occur during the intense laser-mirror interaction, changing the properties of surface-emitted extreme ultraviolet (XUV) radiation, which can then propagate anomalously along the surface."

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New theory claims to unite Einstein's gravity with quantum mechanics
https://phys.org/news/2023-12-theory-ei ... anics.html
by University College London

A radical theory that consistently unifies gravity and quantum mechanics while preserving Einstein's classical concept of spacetime has been announced in two papers published simultaneously by UCL (University College London) physicists.

Modern physics is founded upon two pillars: quantum theory on the one hand, which governs the smallest particles in the universe, and Einstein's theory of general relativity on the other, which explains gravity through the bending of spacetime. But these two theories are in contradiction with each other and a reconciliation has remained elusive for over a century.

The prevailing assumption has been that Einstein's theory of gravity must be modified, or "quantized," in order to fit within quantum theory. This is the approach of two leading candidates for a quantum theory of gravity, string theory and loop quantum gravity.

But a new theory, developed by Professor Jonathan Oppenheim (UCL Physics & Astronomy) and laid out in a paper in Physical Review X, challenges that consensus and takes an alternative approach by suggesting that spacetime may be classical—that is, not governed by quantum theory at all.

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Physicists 'entangle' individual molecules for the first time, hastening possibilities for quantum computing
https://phys.org/news/2023-12-physicist ... ening.html
by Princeton University

For the first time, a team of Princeton physicists have been able to link together individual molecules into special states that are quantum mechanically "entangled." In these bizarre states, the molecules remain correlated with each other—and can interact simultaneously—even if they are miles apart, or indeed, even if they occupy opposite ends of the universe. This research was recently published in the journal Science.

"This is a breakthrough in the world of molecules because of the fundamental importance of quantum entanglement," said Lawrence Cheuk, assistant professor of physics at Princeton University and the senior author of the paper. "But it is also a breakthrough for practical applications because entangled molecules can be the building blocks for many future applications."

These include, for example, quantum computers that can solve certain problems much faster than conventional computers, quantum simulators that can model complex materials whose behaviors are difficult to model, and quantum sensors that can measure faster than their traditional counterparts.

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A micro-ring resonator with big potential: Hybrid device significantly improves laser technology
https://phys.org/news/2023-12-micro-rin ... ybrid.html
by Michael David Mitchell, Ecole Polytechnique Federale de Lausanne

The team at EPFL's Photonic Systems Laboratory (PHOSL) has developed a chip-scale laser source that enhances the performance of semiconductor lasers while enabling the generation of shorter wavelengths.

This pioneering work, led by Professor Camille Brès and postdoctoral researcher Marco Clementi from EPFL's School of Engineering represents a significant advance in the field of photonics, with implications for telecommunications, metrology, and other high-precision applications.

The study, published in the journal Light: Science & Applications, reveals how the PHOSL researchers, in collaboration with the Laboratory of Photonics and Quantum Measurements, have successfully integrated semiconductor lasers with silicon nitride photonic circuits containing microresonators. This integration results in a hybrid device that emits highly uniform and precise light in both near-infrared and visible ranges, filling a technological gap that has long challenged the industry.

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Physicist Discovers 'Paradox-Free' Time Travel Is Theoretically Possible
https://www.sciencealert.com/physicist- ... y-possible

original article: https://iopscience.iop.org/article/10.1 ... 382/aba4bc , article in pdf format

As movies such as The Terminator, Donnie Darko, Back to the Future and many others show, moving around in time creates a lot of problems for the fundamental rules of the Universe: if you go back in time and stop your parents from meeting, for instance, how can you possibly exist in order to go back in time in the first place?

It's a monumental head-scratcher known as the 'grandfather paradox', but a few years ago physics student Germain Tobar, from the University of Queensland in Australia, worked out how to "square the numbers" to make time travel viable without the paradoxes.

"Classical dynamics says if you know the state of a system at a particular time, this can tell us the entire history of the system," Tobar explained back in 2020.

"However, Einstein's theory of general relativity predicts the existence of time loops or time travel – where an event can be both in the past and future of itself – theoretically turning the study of dynamics on its head."

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Breaking the 10-petawatt limit with a new laser amplification
https://phys.org/news/2024-01-petawatt- ... ation.html
by SPIE

Ultra-intense ultrashort lasers have a wide-ranging scope of applications, encompassing basic physics, national security, industrial service, and health care. In basic physics, such lasers have become a powerful tool for researching strong-field laser physics, especially for laser-driven radiation sources, laser particle acceleration, vacuum quantum electrodynamics, and more.

A dramatic increase in peak laser power, from the 1996 1-petawatt "Nova" to the 2017 10-petawatt "Shanghai Super-intense Ultrafast Laser Facility" (SULF) and the 2019 10-petawatt "Extreme Light Infrastructure—Nuclear Physics" (ELI-NP), is due to a shift in gain medium for large-aperture lasers (from neodymium-doped glass to titanium:sapphire crystal). That shift reduced the pulse duration of high-energy lasers from around 500 femtoseconds (fs) to around 25 fs.

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First direct imaging of tiny noble gas clusters at room temperature
https://phys.org/news/2024-01-imaging-t ... sters.html
by University of Vienna

For the first time, a research team has succeeded in stabilizing and directly imaging small clusters of noble gas atoms at room temperature. This achievement opens exciting possibilities for condensed matter physics and applications in quantum information technology.

The key to this breakthrough, achieved by researchers at the University of Vienna in collaboration with colleagues at the University of Helsinki, was the inclusion of noble gas atoms between two graphene layers. This overcomes the difficulty that noble gases do not form stable structures under experimental conditions at room temperature.

Details of the method and the first electron microscopic images of noble gas structures (krypton and xenon) have now been published in Nature Materials .

Jani Kotakoski's group at the University of Vienna was studying the use of ion irradiation to change the properties of graphene and other two-dimensional materials when they noticed something unusual: When noble gases are used for irradiation, they can become trapped between two graphene layers. This happens when the noble gas ions are fast enough to penetrate the first but not the second graphene layer.

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Scientists build mass-producible miniature quantum memory element
https://phys.org/news/2024-01-scientist ... emory.html
by University of Basel

Researchers at the University of Basel have built a quantum memory element based on atoms in a tiny glass cell. In the future, such quantum memories could be mass-produced on a wafer.

It is hard to imagine our lives without networks such as the internet or mobile phone networks. In the future, similar networks are planned for quantum technologies that will enable the tap-proof transmission of messages using quantum cryptography and make it possible to connect quantum computers to each other.

Like their conventional counterparts, such quantum networks require memory elements in which information can be temporarily stored and routed as needed. A team of researchers at the University of Basel led by Professor Philipp Treutlein has now developed such a memory element, which can be micro-fabricated and is, therefore, suitable for mass production. Their results were published in Physical Review Letters.

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Research reveals quantum topological potential in material
https://phys.org/news/2024-01-reveals-q ... erial.html
by Los Alamos National Laboratory

New research into topological phases of matter may spur advances in innovative quantum devices. As described in a new paper published in the journal Nature Communications, a research team including Los Alamos National Laboratory scientists used a novel strain engineering approach to convert the material hafnium pentatelluride (HfTe5) to a strong topological insulator phase, increasing its bulk electrical resistance while lowering it at the surface, a key to unlocking its quantum potential.

"I'm excited that our team was able to show that the elusive and much-sought-after topological surface states can be made to become a predominant electrical conduction pathway," said Michael Pettes, scientist with the Center for Integrated Nanotechnologies (CINT) at the Laboratory.

"This is promising for the development of types of quantum optoelectronic devices, dark matter detectors and topologically protected devices such as quantum computers. And the methodology we demonstrate is compatible for experimentation on other quantum materials."

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Rare decay of the Higgs boson may point to physics beyond the Standard Model

Particle physicists have detected a novel decay of the Higgs boson for the first time, revealing a slight discrepancy in the predictions of the Standard Model and perhaps pointing to new physics beyond it. The findings are published in the journal Physical Review Letters.

The Higgs boson, predicted theoretically since the 1960s, was finally detected in 2012 at the CERN laboratory in Europe. As a quantum field it permeates all of space, through which other particles move, acquiring mass via their interaction with the Higgs field that can be roughly envisioned as a kind of resistance to their motion.

Many properties of the Higgs boson, including how it interacts with other particle and their associated fields, have already been measured to be consistent with predictions of the Standard Model.

But one Higgs decay mode that had yet to be investigated was a theoretical prediction that a Higgs boson would occasionally decay and produce a photon, the quantum of light, and a Z boson, which is an uncharged particle that together with the two W bosons conveys the weak force.

https://phys.org/news/2024-01-rare-deca ... ysics.html

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Room-temperature long-range ferromagnetic order realized in a confined molecular monolayer
https://phys.org/news/2024-01-room-temp ... fined.html
by University of Science and Technology of China

How can we manipulate intermolecular exchange interaction to achieve long-range spin ordering? The answer to this question is of great importance in understanding and modulating magnetic behavior at the microscopic scale and in developing new macroscopic magnetic materials and devices.

However, temperature and environment play a decisive role in molecular magnetic behavior and spin ordering. At high temperatures, thermal uplift disrupts the spin ordering and disables intermolecular exchange interactions.

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Research team takes a fundamental step toward a functioning quantum internet
https://phys.org/news/2024-02-team-fund ... ernet.html
by Stony Brook University

Research with quantum computing and quantum networks is taking place around the world in the hopes of developing a quantum internet in the future. A quantum internet would be a network of quantum computers, sensors, and communication devices that will create, process, and transmit quantum states and entanglement and is anticipated to enhance society's internet system and provide certain services and securities that the current internet does not have.

A team of Stony Brook University physicists and their collaborators have taken a significant step toward the building of a quantum internet testbed by demonstrating a foundational quantum network measurement that employs room-temperature quantum memories. Their findings are described in a paper published in npj Quantum Information.

The field of quantum information essentially combines aspects of physics, mathematics, and classical computing to use quantum mechanics to solve complex problems much faster than classical computing and to transmit information in an unhackable manner.

While the vision of a quantum internet system is growing and the field has seen a surge in interest from researchers and the public at large, accompanied by a steep increase in the capital invested, an actual quantum internet prototype has not been built.

According to the Stony Brook research team, the key hurdle to achieve the potential of making communication networks more secure, measurement systems more precise, and algorithms for certain scientific analyses more powerful, relies on developing systems capable of bringing quantum information and entanglement across many nodes and over long distances. These systems are called quantum repeaters and are one of the more complex challenges in current physics research.

The researchers have advanced quantum repeater capacities in their latest experimentation. They built and characterized quantum memories that operate at room temperature and demonstrated that these memories have identical performance, an essential feature when the goal is to build large-scale quantum repeater networks that will comprise several of these memories.

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Quantum materials: A new state of matter with chiral properties
https://phys.org/news/2024-02-quantum-m ... rties.html
by Ca' Foscari University of Venice

An international research group has discovered a new state of matter characterized by the existence of a quantum phenomenon called chiral current. These currents are generated on an atomic scale by a cooperative movement of electrons, unlike conventional magnetic materials whose properties originate from the quantum characteristic of an electron known as spin and their ordering in the crystal.

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Flowermon: A superconducting qubit based on twisted cuprate van der Waals heterostructures
https://phys.org/news/2024-02-flowermon ... prate.html
by Ingrid Fadelli , Phys.org

Quantum technology could outperform conventional computers on some advanced optimization and computational tasks. In recent years, physicists have been working to identify new strategies to create quantum systems and promising qubits (i.e., basic units of information in quantum computers).

Researchers at the Institute for Complex Systems of CNR (Consiglio Nazionale delle Ricerche), Max Planck Institute for Chemical Physics of Solids, and other institutes worldwide have recently introduced a new superconducting and capacitively shunted qubit, which they dubbed "flowermon." This qubit, introduced in Physical Review Letters, is based on twisted cuprate van der Waals heterostructures.

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Scientists report first look at electrons moving in real-time in liquid water
https://phys.org/news/2024-02-scientist ... iquid.html
by Pacific Northwest National Laboratory

In an experiment akin to stop-motion photography, scientists have isolated the energetic movement of an electron while "freezing" the motion of the much larger atom it orbits in a sample of liquid water.

The findings, reported in the journal Science, provide a new window into the electronic structure of molecules in the liquid phase on a timescale previously unattainable with X-rays. The new technique reveals the immediate electronic response when a target is hit with an X-ray, an important step in understanding the effects of radiation exposure on objects and people.

"The chemical reactions induced by radiation that we want to study are the result of the electronic response of the target that happens on the attosecond timescale," said Linda Young, a senior author of the research and Distinguished Fellow at Argonne National Laboratory.

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Diamond quantum memory with Germanium vacancy exceeds coherence time of 20 ms
https://phys.org/news/2024-02-diamond-q ... cancy.html
by Ingrid Fadelli , Phys.org

The color centers of diamond are the focus of an increasing number of research studies, due to their potential for developing quantum technologies. Some works have particularly explored the use of negatively-charged group-IV diamond defects, which exhibit an efficient spin-photon interface, as the nodes of quantum networks.

Researchers at Ulm University in Germany recently leveraged a Germanium vacancy (GeV) center in diamond to realize a quantum memory. The resulting quantum memory, presented in a Physical Review Letters paper, was found to exhibit a promising coherence time of more than 20 ms.

"Our research group's primary focus is the exploration of diamond color centers for quantum applications," Katharina Senkalla, co-author of the paper, told Phys.org. "The most popular defect of diamond so far has been the nitrogen-vacancy center, but, recently, other color centers have also become a focus of research. These consist of an element from the IV column of the periodic table—Si, Ge, Sn or Pb, and a lattice vacancy (i.e., missing next-neighbor carbon atom)."