Lifeboat Foundation

The protons and neutrons in a nucleus can form clusters analogous to atoms in a molecule, even in the nuclear ground state.

Heisenberg’s uncertainty principle limits the precision with which two observables that do not commute with each other can be simultaneously measured. The Wigner-Araki-Yanase (WAY) theorem goes further. If observables A and B do not commute, and if observable A is conserved, observable B cannot be measured with arbitrary precision even if A is not measured at all. In its original 1960 formulation, the WAY theorem applied only to observables, such as spin, whose possible values are discrete and bounded. Now Yui Kuramochi of Kyushu University and Hiroyasu Tajima of the University of Electro-Communications—both in Japan—have proven that the WAY theorem also encompasses observables, such as position, that are continuous and unbounded [1]. Besides resolving the decades-long problem of how to deal with such observables, the extension will likely find practical applications in quantum optics.

The difficulty of extending the WAY theorem arose from how an unbounded observable L is represented: as an infinite-dimensional matrix with unbounded eigenvalues. To tame the problem, Kuramochi and Tajima avoided considering L directly. Instead, they looked at an exponential function of L, which forms a one-parameter unitary group. Although the exponential function is also unbounded, its spectrum of eigenvalues is contained within the complex plane’s unit circle. Thanks to that boundedness, Kuramochi and Tajima could go on to use off-the-shelf techniques from quantum information to complete their proof.

Because momentum is conserved, the extended WAY theorem implies that a particle’s position cannot be measured with arbitrary precision even if its momentum is not measured simultaneously. Similar pairs of observables crop up in quantum optics. Kuramochi and Tajima anticipate that their theorem could be useful in setting limits on the extent to which quantum versions of transmission protocols can outperform the classical ones.

Light confined to an accelerating optical cavity could display a photonic counterpart of the electronic quantum Hall effect.

Place a conductor in a magnetic field and the electrical current driven by an applied voltage will not flow in a straight line but in a direction perpendicular to the electric field—a behavior known as the Hall effect [1]. Reduce the temperature to the point where the electrons manifest quantum-mechanical behavior, and the plot thickens. The conductivity (defined as the ratio between the sideways current and the voltage) exhibits discrete jumps as the magnetic field is varied—the quantum Hall effect [2]. Since electrons at low temperature and photons obey a similar wave equation [3], should we also expect a quantum Hall effect for light? This question has been bubbling under the surface for the past decade, leading to the observation of some aspects of an optical quantum Hall effect [4, 5]. But the analogy between photons and electrons remains incomplete.

For the first time, researchers have succeeded in selectively exciting a molecule using a combination of two extreme-ultraviolet light sources and causing the molecule to dissociate while tracking it over time. This is another step towards specific quantum mechanical control of chemical reactions, which could enable new, previously unknown reaction channels.

The interaction of light with matter, especially with molecules, plays an important role in many areas of nature, for example in biological processes such as photosynthesis. Technologies such as solar cells use this process as well.

On the Earth’s surface, mainly light in the visible, ultraviolet or infrared regime plays a role here. Extreme-ultraviolet (XUV) light—radiation with significantly more energy than visible light —is absorbed by the atmosphere and therefore does not reach the Earth’s surface. However, this XUV radiation can be produced and used in the laboratory to enable a selective excitation of electrons in molecules.

Refractory organic pollutants, including phenols, perfluorinated compounds, and antibiotics, are abundant in various industrial wastewater streams such as chemical, pharmaceutical, coking, and dyeing sectors, as well as municipal and domestic sources. These pollutants pose significant threats to ecological well-being and human health.

The imperative to achieve complete removal of organic contaminants from water and facilitate water recycling is paramount for enhancing environmental quality and ensuring sustainable economic and social progress. Addressing the efficient removal of recalcitrant organic pollutants in water is not only a focal point in environmental chemical pollution control research but also a pivotal technical challenge constraining industrial wastewater reuse.

Advanced oxidation processes (AOPs), especially heterogeneous AOPs, yield strongly reactive oxygen species including ·OH, ·O₂^-, and ·SO₄^- to oxidize organic pollutants under ambient conditions, are appealing wastewater treatment technologies for decentralized systems. AOPs often need excessive energy input (UV light or electricity) to activate soluble oxidants (H₂O₂, O₃, persulfates), thus more cost-effective AOPs are urgently required.

In laser-based manufacturing, accommodating non-flat, or changing surfaces has traditionally been labor-intensive, involving complex focus mapping procedures and or ex-situ characterization. This often results in repositioning errors and extended processing times.

To address these issues, ultra-high-speed auto-focusing in laser processing has been developed. Whereas most auto-focusing techniques still require the mechanical motion of a motorized stage. This mechanical movement in the beam propagation axis can be significantly slower than the lateral speed, slowing down the process of surface detection and re-alignment. Furthermore, it requires feedback, control, and sensing methods in order to determine the optical focal position.

In a new paper published in Light: Science & Applications, a team of researchers, led by Professor Craig B. Arnold from the Department of Mechanical and Aerospace Engineering at Princeton University, U.S., developed a fast method to simultaneously track the specific location of a surface and adjust the focus of an optical system. They employed axial varifocal optics, specifically a TAG lens, which operates at 0.1−1 MHz, bypassing delays from the mechanical motion in the beam propagation direction.

Glass is a material that appears simple in its transparency and rigidity but is, in fact, highly complex and intriguing. Its transformation from a liquid to glass, known as the “glass transition,” is marked by a significant slowdown in its dynamics, giving glass its distinctive properties.

This transformation has been a subject of scientific curiosity for years. A particularly interesting aspect of this process is the emergence of “dynamical heterogeneities.” As the liquid cools and nears the glass transition temperature, its dynamics become more correlated and intermittent.

An open-source advanced supercomputer algorithm predicts the patterning and dynamics of living materials, allowing for the exploration of their behaviors across space and time.

Biological materials consist of individual components, including tiny motors that transform fuel into motion. This process creates patterns of movement, leading the material to shape itself through coherent flows driven by constant energy consumption. These perpetually driven materials are called “active matter.”

The mechanics of cells and tissues can be described by active matter theory, a scientific framework to understand the shape, flows, and form of living materials. The active matter theory consists of many challenging mathematical equations.

Quantum scientists have discovered a phenomenon in purple bronze, a one-dimensional metal, that allows it to switch between insulating and superconducting states. This switch, triggered by minimal stimuli like heat or light, is due to ’emergent symmetry’. This groundbreaking finding, initiated by research into the metal’s magnetoresistance, could lead to the development of perfect switches in quantum devices, a potential milestone in quantum technology.

Quantum scientists have discovered a phenomenon in purple bronze that could be key to the development of a ‘perfect switch’ in quantum devices which flips between being an insulator and superconductor.

The research, led by the University of Bristol and published in Science, found these two opposing electronic states exist within purple bronze, a unique one-dimensional metal composed of individual conducting chains of atoms.