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Extending the Adiabatic Theorem

Jerk the support from which a swinging pendulum hangs, and you will change the pendulum’s motion. But move the support very gradually, and the system will adapt so that the pendulum’s motion relative to its support remains unchanged. A similar principle holds true for quantum systems. The quantum adiabatic theorem says that a system, when perturbed sufficiently slowly, remains in its instantaneous ground state. Sarah Damerow and Stefan Kehrein of the University of Göttingen in Germany now show that aspects of this principle remain true even for the opposite limit: The ground state remains the single most likely state even for a quantum system subjected to an instantaneous perturbation [1].

Formally, the quantum adiabatic theorem describes how a perturbed system’s Hamiltonian evolves in time. It shows that, for a slow perturbation, the system transitions from its initial ground state to the time-evolved Hamiltonian’s ground state with a probability greater than the combined probabilities of all the excited states.

Damerow and Kehrein used analytical and numerical tools to examine a quantum system undergoing rapid perturbation. They considered a quantum Ising model—a lattice of interacting magnetic spins—subjected to a rapidly changing external field. They found that the system was more likely to evolve from its initial ground state to the time-evolved Hamiltonian’s ground state than to any given excited state—provided that the lattice was in the same magnetic phase (paramagnetic or ferromagnetic) in both ground states.

Building desktop particle accelerators to unlock new realms of research

Using high-intensity lasers, researchers have taken an important step toward miniaturization of particle accelerators by demonstrating free-electron laser amplification at extreme ultraviolet wavelengths (27–50 nm), with an acceleration length of only a few millimeters. By generating high-quality, monoenergetic electron beams (i.e. beams where all the electrons have nearly the same energy), they have achieved a key milestone toward compact accelerator technologies.

The work is published in the journal Physical Review Research.

The research team led by The University of Osaka’s Institute of Scientific and Industrial Research (SANKEN) in collaboration with Kansai Institute for Photon Science (KPSI), National Institutes for Quantum Science and Technology (QST), RIKEN SPring-8 Center (RSC), High Energy Accelerator Research Organization (KEK), used a technique called laser wakefield acceleration to create plasma waves that generate extremely strong accelerating electric fields, thanks to waves within the plasma that travel at almost the speed of light.

Helical liquid crystals can flip light’s chirality under ultralow electric fields

The direction in which the electromagnetic field of circularly polarized light rotates can be easily reversed by applying a voltage, RIKEN researchers have demonstrated. This could enable a new generation of optical devices based on circularly polarized light. The work is published in two papers in the journal Advanced Materials.

Polarized sunglasses produce light that is polarized along a single direction. But some special devices can generate light with a polarization that rotates as the light propagates. Such circularly polarized light is useful for many applications, including spectroscopy, satellite communications, stereoscopy and microscopy.

For some applications, it would be useful to switch between clockwise and anticlockwise circularly polarized light. However, this handedness is locked into the molecular structure. Known as the material’s chirality, it is used to produce the circularly polarized light. And reversing that requires a lot of energy.

Useful quantum computers could be built with as few as 10,000 qubits, team finds

Quantum computers of the future may be closer to reality thanks to new research from Caltech and Oratomic, a Caltech-linked start-up company. Theorists and experimentalists teamed up to develop a new approach for reducing the errors that riddle today’s rudimentary quantum computers. Whereas these machines were previously thought to require millions of qubits to work properly (qubits being the quantum equivalent to 1’s and 0’s in classical computers), the new results indicate that a fully realized quantum computer could be built with as few as 10,000 to 20,000 qubits. The need for fewer qubits means that quantum computers could, in theory, be operational by the end of the decade.

The team proposes a new quantum error-correction architecture that is significantly more efficient than previous approaches. Quantum error correction is a process by which extra, redundant qubits are introduced to correct errors, or faults, enabling the ultimate goal in the field: fault-tolerant quantum computing.

The results exploit special properties of quantum computing platforms built out of neutral atoms, which serve as the qubits. Alternative platforms in development include superconducting circuits and trapped ions (ions are charged whereas neutral atoms are not). In a neutral atom system, laser beams known as optical tweezers are used to arrange atoms into qubit arrays. Manuel Endres, a professor of physics at Caltech, and his colleagues recently created the largest qubit array ever assembled, containing 6,100 trapped neutral atoms.

Ultrafast quantum light pulses measured for the first time

Researchers at the Technion—Israel Institute of Technology have, for the first time, measured the temporal duration of individual pulses of an extraordinary form of quantum light known as bright squeezed vacuum (BSV). Their findings are published in Optica.

Bright squeezed vacuum is a unique quantum state of light. Although it is formally considered the “vacuum state” and the electric field of this light is zero on average, it exhibits enormous quantum fluctuations of its electric field due to the squeezing effect.

This is in stark contrast to typical light produced by intense lasers, known as coherent-state light, that exhibit only extremely weak quantum fluctuations. However, for BSV, the fluctuations can lead to extremely intense light pulses, containing up to one trillion (10¹²) photons in a single pulse, hence the term bright squeezed vacuum. Until now, no one had measured the temporal duration of single BSV pulses.

Unexplained sky flashes from the 1950s: Independent analysis supports their existence

Historical observations from an observatory in Germany have now independently verified evidence for brief, mysterious flashes of light in the night sky, first picked up by an American astronomical survey in the 1950s. Through fresh analysis of a German survey from the same period, independent researcher Ivo Busko, a now-retired developer at NASA, has uncovered striking new support for these puzzling signals. The results have been published as a preprint on arXiv.

In 2019, an international team of astronomers launched the VASCO Project, aiming to identify unusual phenomena hidden within vast archives of historical data. In particular, their work focused on astronomical transients: objects that suddenly appear in the sky in some images, but vanish in subsequent observations.

An especially exciting result emerged in 2025, when researchers analyzed photographic plates captured as part of the Palomar Observatory Sky Survey. Carried out in California throughout the 1950s, this ambitious program produced nearly 2,000 images of the night sky using long-exposure plates. Within these images, the team found clear evidence of transients with strange appearance and behavior, captured at a time that predates the launch of any human-made satellites.

Chaos shapes how meandering rivers change over time, research shows

Rivers are rarely the calm, orderly streams we imagine on maps. Over time, their winding paths—called meanders—shift, bend, and occasionally snap off in sudden “cutoff” events that shorten loops and reshape the landscape. While scientists have long suspected that such cutoffs inject a dose of unpredictability into river evolution, a new study published in Communications Earth & Environment demonstrates that these abrupt events are, by themselves, enough to produce chaos in river channels.

Harvard Ph.D. candidate Brayden Noh and NYU Tandon Assistant Professor Omar Wani used a widely used computational model to explore how meandering rivers evolve over time. This model isolates the essential dynamics: bends migrate laterally in proportion to curvature, and loops are occasionally severed through cutoffs. Other real-world complexities—like sediment transport, bank composition, and vegetation—are treated as secondary, allowing the researchers to focus squarely on the geometry-driven behavior of rivers.

To test the role of cutoffs, the team simulated rivers starting from nearly identical initial shapes, then introduced infinitesimally small perturbations to each of the multiple copies. They tracked how the channels diverged over time by mapping their evolving shapes onto a fixed grid and measuring differences cell by cell. In a striking counterfactual experiment, when cutoffs were disabled, the two channels stayed nearly identical over large time horizons. When cutoffs were allowed, even tiny initial differences grew exponentially, a hallmark of deterministic chaos.

Gravitational waves as possible candidates for the origin of dark matter

Gravitational waves could be responsible for the production of dark matter during the early phases of our universe’s formation, according to results of a new study by Professor Joachim Kopp from Johannes Gutenberg University Mainz (JGU) and the PRISMA Cluster of Excellence in cooperation with Dr. Azadeh Maleknejad from Swansea University. Their work, published in Physical Review Letters, presents new calculations that explore a novel mechanism for the formation of dark matter through so-called stochastic gravitational waves.

In this way, they contribute to answering a fundamental question in particle physics. Planets, stars, and even life on Earth are all composed of visible matter. This type of matter only makes up about 4% of our universe. The vast majority is invisible, consisting of dark matter and dark energy. For instance, dark matter makes up about 23% of our universe.

Astrophysical observations confirm that dark matter permeates the whole universe and forms galaxies as well as the largest known structures in the cosmos. However, the particles that make up dark matter are still unknown. Many theories and ongoing experiments are looking for an answer to this open question.

Superconductivity switched on in material once thought only magnetic

Superconductivity—the ability of a material to conduct electricity without any energy loss to heat—enables highly efficient, ultra-fast electronics essential for advanced technologies such as magnetic resonance imaging (MRI) machines, particle accelerators and, potentially, quantum computers. New research has now revealed that iron telluride (FeTe), a compound composed of the chemical elements iron and tellurium and long thought to be an ordinary magnetic metal, is in fact a superconductor. The researchers found that hidden excess iron atoms induce the material’s magnetism, and removing these atoms allows electricity to flow with zero resistance.

Two papers describing the research, both led by Penn State Professor of Physics Cui-Zu Chang, were published back-to-back today (April 1) in the journal Nature. The first paper focuses on how to “switch on” superconductivity in FeTe, while the second paper reveals a new kind of “quantum dance,” where superconductivity interacts with the material’s atomic structure when a different top layer is added, allowing researchers to tune its behavior.

“Unlike the well-known iron-based superconductor iron selenide (FeSe), FeTe has long been considered a magnetic metal without superconductivity, despite having an almost identical crystal structure,” Chang said. “It has remained a mystery why FeTe doesn’t share this important property.”

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