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Category: quantum physics

Elusive Quantum Interactions Tracked During Cooling

Over the past few decades, researchers have used ultracold atomic gases to simulate high-temperature superconductors and other materials in which electrons interact strongly. Frustratingly, these experiments have failed to uncover the temperature dependence of certain “p-wave” interactions relevant to some superconductors and superfluids. Now Kenta Nagase and his colleagues at the Institute of Science Tokyo have tracked how these interactions change as a cloud of lithium atoms is cooled toward absolute zero [1]. The results could help scientists better understand the behavior of certain exotic superconductors.

In a p-wave interaction, particles collide with each other in such a way that their interaction strength depends on their relative orientations. The inherent complexity of these interactions, such as their occurrence through three different scattering channels, meant that their predicted temperature dependence lacked experimental confirmation. To surmount this hurdle, Nagase and his colleagues isolated and analyzed the contributions to the interactions from each channel. They repeated their experiment at many temperatures, controlled by the strength of the optical trap confining the lithium cloud.

As they cooled the lithium cloud, Nagase and his colleagues saw that the strength of p-wave interactions increased, in agreement with predictions. These interactions caused the lithium atoms to briefly form fragile molecules, mimicking the pairing of electrons in a superconductor. The measured number, angular distribution, and behavior of such molecules were also consistent with expectations. These properties had been explored in the lab only partially, so the new work provides stronger support for current models of ultracold atomic gases.

An ultra-fast quantum tunneling device for the 6G terahertz era

A research team affiliated with UNIST has unveiled a quantum device, capable of ultra-fast operation, a key step toward realizing technologies like 6G communications. This innovation overcomes a major hurdle that has long limited the durability of such devices under high electrical fields.

Professor Hyeong-Ryeol Park from the Department of Physics at UNIST, in collaboration with Professor Sang Woon Lee at Ajou University, has developed a terahertz quantum device that can operate reliably without suffering damage from intense electric fields—something that has been a challenge for existing technologies.

What Happens When Light Gains Extra Dimensions

Shaped quantum light is turning ordinary photons into powerful tools for the future of technology.

A global group of scientists, including researchers from the UAB, has published a new review in Nature Photonics exploring a rapidly developing area of research called quantum structured light. This field is changing how information can be sent, measured, and processed by combining quantum physics with carefully designed patterns of light in space and time. By doing so, researchers can create photons capable of carrying far more information than traditional light.

From qubits to higher dimensional quantum states.

Physicists made atoms behave like a quantum circuit

Using ultracold atoms and laser light, researchers recreated the behavior of a Josephson junction—an essential component of quantum computers and voltage standards. The appearance of Shapiro steps in this atomic system reveals a deep universality in quantum physics and makes elusive microscopic effects visible for the first time.

Josephson junctions play a central role in modern physics and technology. They enable extremely precise measurements, define the international standard for electrical voltage, and serve as essential components inside many quantum computers. Despite their importance, the quantum-scale processes occurring inside superconductors are notoriously difficult to observe directly.

To overcome this challenge, researchers at the RPTU University of Kaiserslautern-Landau turned to quantum simulation. Instead of studying electrons inside a solid material, they recreated the Josephson effect using ultracold atoms. Their approach involved separating two Bose-Einstein condensates (BECs) with an exceptionally thin optical barrier created by a focused laser beam that was moved in a controlled, periodic way. Even in this atomic system, the defining signatures of Josephson junctions emerged. The experiment revealed Shapiro steps, which are distinct voltage plateaus that appear at multiples of a driving frequency, just as they do in superconducting devices. Published in the journal Science, the work stands as a clear example of how quantum simulation can uncover hidden physics.

Entanglement enhances the speed of quantum simulations, transforming long-standing obstacles into a powerful advantage

Researchers from the Faculty of Engineering at The University of Hong Kong (HKU) have made a significant discovery regarding quantum entanglement. This phenomenon, which has long been viewed as a significant obstacle in classical quantum simulations, actually enhances the speed of quantum simulations. The findings are published in Nature Physics in an article titled “Entanglement accelerates quantum simulation.”

Simulating the dynamic evolution of matter is fundamental to understanding the universe, yet it remains one of the most challenging tasks in physics and chemistry. For decades, “entanglement”—the complex correlation between quantum particles—has been viewed as a formidable barrier. In classical computing, high entanglement makes simulations exponentially harder to perform, often acting as a bottleneck for studying complex quantum systems.

Led by Professor Qi Zhao from the School of Computing and Data Science at HKU, the research team collaborated with Professor You Zhou from Fudan University and Professor Andrew M. Childs from the University of Maryland, and overturned this long-held belief. They discovered that while entanglement hinders classical computers, it actually accelerates quantum simulations, turning a former obstacle into a powerful resource.

Unexpected oscillation states in magnetic vortices could enable coupling across different physical systems

Researchers at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) have uncovered previously unobserved oscillation states—so-called Floquet states—in tiny magnetic vortices. Unlike earlier experiments, which required energy-intensive laser pulses to create such states, the team in Dresden discovered that a subtle excitation with magnetic waves is sufficient.

This finding not only raises fundamental questions in basic physics but could also eventually serve as a universal adapter bridging electronics, spintronics, and quantum devices. The team reports the results in the journal Science.

Magnetic vortices can form in ultrathin, micron-sized disks of magnetic materials such as nickel–iron. Within these vortices, the elementary magnetic moments—tiny compass needles—arrange themselves in circular patterns.

Quantum-enhanced interferometry amplifies detection of tiny laser beam shifts and tilts

A quantum trick based on interferometric measurements allows a team of researchers at LMU to detect even the smallest movements of a laser beam with extreme sensitivity.

Precisely measuring minute shifts or slight tilts of a laser beam is crucial in many scientific and technological applications, such as atomic force microscopy. So-called weak value amplification (WVA), a method that grew out of thinking about the foundations of quantum mechanics, has already shown that under certain conditions the output signal of an interferometer changes markedly when the beams inside it are altered only minimally. An interferometer is a measuring device that can detect such tiny differences by comparing overlapping light waves.

LMU physicist Carlotta Versmold and her colleagues, all members of the MCQST Cluster of Excellence, working together with researchers at Tel Aviv University, have now extended this type of measurement. The team recently developed a trick that also amplifies changes in the incoming beam. This makes it possible to carry out far more precise measurements that were previously difficult to achieve. A laser beam reflected from a distant window, for example, could pick up vibrations in the glass caused by conversations inside the building, allowing those conversations to be overheard.

Replication efforts suggest ‘smoking gun’ evidence isn’t enough to prove quantum computing claims

A group of scientists, including Sergey Frolov, professor of physics at the University of Pittsburgh, and co-authors from Minnesota and Grenoble have undertaken several replication studies centered around topological effects in nanoscale superconducting or semiconducting devices. This field is important because it can bring about topological quantum computing, a hypothetical way of storing and manipulating quantum information while protecting it against errors.

In all cases, they found alternative explanations of similar data. While the original papers claimed advances for quantum computing and made their way into top scientific journals, the individual follow-ups could not make it past the editors at those same journals.

Reasons given for its rejection included that, being a replication, it was not novel; that, after a couple of years, the field had moved on. But replications take time and effort and the experiments are resource-intensive and cannot happen overnight. And important science does not become irrelevant on the scale of years.

Quantum phenomenon enables a nanoscale mirror that can be switched on and off

Controlling light is an important technological challenge—not just at the large scale of optics in microscopes and telescopes, but also at the nanometer scale. Recently, physicists at the University of Amsterdam published a clever quantum trick that allows them to make a nanoscale mirror that can be turned on and off at will.

The work is published in the journal Light: Science & Applications.

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