Physics News and Discussions

[weatheriscool]

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

[weatheriscool]

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.

[weatheriscool]

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."

[weatheriscool]

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."

[weatheriscool]

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."

[weatheriscool]

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.

[weatheriscool]

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.

[weatheriscool]

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.

[weatheriscool]

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."

[weatheriscool]

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.