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Category: quantum physics – Page 9

To detect the quantum tornado in momentum space, the Würzburg team enhanced a well-known technique called ARPES (angle-resolved photoemission spectroscopy). “ARPES is a fundamental tool in experimental solid-state physics. It involves shining light on a material sample, extracting electrons, and measuring their energy and exit angle. This gives us a direct look at a material’s electronic structure in momentum space,” explains Ünzelmann. “By cleverly adapting this method, we were able to measure orbital angular momentum. I’ve been working with this approach since my dissertation.”

ARPES is rooted in the photoelectric effect, first described by Albert Einstein and taught in high school physics. Ünzelmann had already refined the method in 2021, gaining international recognition for detecting orbital monopoles in tantalum arsenide. Now, by integrating a form of quantum tomography, the team has taken the technique a step further to detect the quantum tornado — another major milestone. “We analyzed the sample layer by layer, similar to how medical tomography works. By stitching together individual images, we were able to reconstruct the three-dimensional structure of the orbital angular momentum and confirm that electrons form vortices in momentum space,” Ünzelmann explains.

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Newly achieved precise control over light emitted from incredibly tiny sources, a few nanometers in size, embedded in two-dimensional (2D) materials could lead to remarkably high-resolution monitors and advances in ultra-fast quantum computing, according to an international team led by researchers at Penn State and Université Paris-Saclay.

In a recent study, published in ACS Photonics, scientists worked together to show how the light emitted from 2D materials can be modulated by embedding a second 2D material inside them — like a tiny island of a few nanometers in size — called a nanodot. The team described how they achieved the confinement of nanodots in two dimensions and demonstrated that, by controlling the nanodot size, they could change the color and frequency of the emitted light.

“If you have the opportunity to have localized light emission from these materials that are relevant in quantum technologies and electronics, it’s very exciting,” said Nasim Alem, Penn State associate professor of materials science and engineering and co-corresponding author on the study. “Envision getting light from a zero-dimensional point in your field, like a dot in space, and not only that, but you can also control it. You can control the frequency. You can also control the wavelength where it comes from.”

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What happens when a quantum physicist is frustrated by the limitations of quantum mechanics when trying to study densely packed atoms? At EPFL, you get a metamaterial, an engineered material that exhibits exotic properties.

That frustrated physicist is Ph.D. student Mathieu Padlewski. In collaboration with Hervé Lissek and Romain Fleury at EPFL’s Laboratory of Wave Engineering, Padlewski has built a novel acoustic system for exploring condensed matter and their macroscopic properties, all the while circumventing the extremely sensitive nature that is inherent to . Moreover, the can be tweaked to study properties that go beyond solid-state physics. The results are published in Physical Review B.

“We’ve essentially built a playground inspired by that can be adjusted to study various systems. Our metamaterial consists of highly tunable active elements, allowing us to synthesize phenomena that extend beyond the realm of nature,” says Padlewski. “Potential applications include manipulating waves and guiding energy for telecommunications, and the setup may one day provide clues for harvesting energy from waves for instance.”

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Interferometers, devices that can modulate aspects of light, play the important role of modulating and switching light signals in fiber-optic communications networks and are frequently used for gas sensing and optical computing.

Now, applied physicists at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have invented a new type of interferometer that allows precise control of light’s frequency, intensity and mode in one compact package.

Called a cascaded-mode interferometer, it is a single waveguide on a silicon-on-insulator platform that can create multiple signal paths to control the amplitude and phase of light simultaneously, a process known as optical spectral shaping. By combining mechanisms to manipulate different aspects of light into a single waveguide, the could be used in advanced nanophotonic sensors or on-chip quantum computing.

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A hidden quantum wave may keep particles moving, even when everything else freezes. Researchers discovered that phasons, a type of low-temperature quasiparticle found in crystal lattices, allow interlayer excitons to move, even at temperatures where motion is expected to stop.

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The standard model of particle physics is our best theory of the elementary particles and forces that make up our world: particles and antiparticles, such as electrons and positrons, are described as quantum fields. They interact through other force fields, such as the electromagnetic force that binds charged particles.

To understand the behavior of these quantum fields—and with that, our universe—researchers perform complex computer simulations of quantum field theories. Unfortunately, many of these calculations are too complicated for even our best supercomputers and pose great challenges for quantum computers as well, leaving many pressing questions unanswered.

Using a novel type of quantum computer, Martin Ringbauer’s experimental team at the University of Innsbruck, and the theory group led by Christine Muschik at IQC at the University of Waterloo, Canada, report in Nature Physics on how they have successfully simulated a complete quantum field theory in more than one spatial dimension.

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Time travel has long fascinated scientists and theorists, prompting questions about whether the future can send visitors into its own past and whether individuals could move forward in time in ways that bypass the normal flows of daily life. The general idea of time as a fourth dimension, comparable to spatial dimensions, gained traction when Hermann Minkowski famously stated that “space by itself, and time by itself, are doomed to fade away into mere shadows” (Minkowski, 1908, p. 75). This integrated view of spacetime underlies many physics-based theories of how a traveler might move along the temporal axis.

In relativity, closed timelike curves (CTCs) theoretically allow a path through spacetime that loops back to its origin in time. As Kip Thorne put it, “wormhole physics is at the very forefront of our understanding of the Universe” (Thorne, 1994, pp. 496–497). A wormhole with suitable geometry might permit travel from one point in time to another. However, such scenarios raise paradoxes. One common example is the “grandfather paradox,” which asks how a traveler could exist if they venture into the past and eliminate their own ancestor. David Deutsch offered one possible resolution by suggesting that “quantum mechanics may remove or soften the paradoxes conventionally associated with time travel” (Deutsch, 1991, p. 3198). His reasoning rests on the idea that quantum behavior might allow timelines to branch or otherwise circumvent contradictions.

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Imagine building a Lego tower with perfectly aligned blocks. Each block represents an atom in a tiny crystal, known as a quantum dot. Just like bumping the tower can shift the blocks and change its structure, external forces can shift the atoms in a quantum dot, breaking its symmetry and affecting its properties.

Scientists have learned that they can intentionally cause symmetry breaking—or symmetry restoration—in quantum dots to create new materials with unique properties. In a recent study, researchers at the U.S. Department of Energy’s (DOE) Argonne National Laboratory have discovered how to use light to change the arrangement of atoms in these minuscule structures.

Quantum dots made of semiconductor materials, such as lead sulfide, are known for their unique optical and due to their tiny size, giving them the potential to revolutionize fields such as electronics and medical imaging. By harnessing the ability to control symmetry in these quantum dots, scientists can tailor the materials to have specific light and electricity-related properties. This research opens up new possibilities for designing materials that can perform tasks previously thought impossible, offering a pathway to innovative technologies.

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Scholars at the School of Engineering of the Hong Kong University of Science and Technology (HKUST) have unveiled an innovation that brings artificial intelligence (AI) closer to quantum computing—both physically and technologically.

Led by Prof. Shao Qiming, Assistant Professor at the Department of Electronic and Computer Engineering, the research team has developed a new computing scheme that works at extremely low temperatures. As a critical advancement in quantum computing, it can significantly reduce latency between artificial intelligence (AI) agents and quantum processors while boosting energy efficiency. The solution was made possible by utilizing a special technology known as magnetic topological insulator Hall-bar devices.

This latest invention addresses a major challenge concerning the operational environment and hardware requirements of quantum computers, amid growing interest in the amalgamation of quantum computing—widely seen as the future of high-speed and high-efficiency computing, with artificial intelligence—a fast-evolving technology.

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Researchers at QuTech, in collaboration with Fujitsu and Element Six, have demonstrated a complete set of quantum gates with error probabilities below 0.1%. While many challenges remain, being able to perform basic gate operations with errors occurring below this threshold, satisfies an important condition for future large-scale quantum computation. The research was published in Physical Review Applied on 21 March 2025.

Quantum computers are anticipated to be able to solve important problems that are beyond the capabilities of classical computers. Quantum computations are performed through a large sequence of basic operations, called .

For a quantum computer to function, it is essential that all quantum gates are highly precise. The probability of an error during the gates must be below a threshold, typically of the order 0.1 to 1%. Only then, errors are rare enough for error correction methods to work successfully and ensure reliable with noisy components.

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