AI model AlphaGenome forecasts the consequences of altering every single DNA letter in the human genome.
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To Lase or Not to Lase: The Question of Neutrino Superradiance
Two studies find that fundamental quantum constraints rule out a previously proposed neutrino-laser scheme.
One of the most striking demonstrations of collective quantum behavior is superradiance. When photons emitted by many particles carry no information about which particle produced them, the different emission pathways interfere constructively, and the ensemble radiates far more intensely than independent emitters would. Last year, scientists proposed that this principle could extend from photons to neutrinos, potentially enabling the first neutrino laser (see Viewpoint: Envisioning a Neutrino Laser) [1]. The idea was especially appealing because neutrinos are otherwise extremely difficult to control and detect, owing to their weak interactions with matter. Now Wolfgang Ketterle and his colleagues at MIT have demonstrated that this vision of neutrino superradiance runs up against fundamental constraints—ones imposed not by engineering challenges but by quantum mechanics itself [2, 3].
Superradiance is a collective enhancement of spontaneous emission [4]. An isolated atom emits at its natural rate γ so N independent atoms radiate at a total rate N γ But when all the atoms radiate into the same mode, constructive interference of the different emission pathways can cause the maximum emission rate to scale as N2 γ This superradiant regime can occur when the atoms occupy a region much smaller than the radiation’s wavelength or when an optical cavity forces them to couple to a common mode [5–7]. Such collective emission can also arise in extended atomic systems, where it becomes directional and is shaped by propagation effects. This extended-ensemble superradiance has been observed in free space [8] and in waveguides [9].
A photon that challenges Einstein: According to current physics, it should never have reached Earth
How did a photon survive a journey of more than 2 billion light-years when, according to known physics, it should have been absorbed long before reaching Earth? This is the question at the heart of a new study by Giorgio Galanti (INAF) and Marco Roncadelli (INFN), accepted for publication in Physical Review Letters.
The research addresses one of the most fascinating puzzles in contemporary astrophysics. It proposes a possible explanation for the highest-energy photon ever observed from a gamma-ray burst, suggesting that under extreme conditions spacetime may behave differently from what Einstein’s theory of relativity predicts.
At the center of the story is the brightest gamma-ray burst ever observed, GRB 221009A, nicknamed BOAT by astronomers—the Brightest Of All Time. The explosion, which occurred about 2 billion light-years from Earth and was observed on Oct. 9, 2022, reached our planet as an enormous shower of photons, the elementary particles of light.
A new game demonstrates quantum advantage with provable classical limits
For decades, physicists have worked to prove the strange predictions of quantum mechanics with real experiments. As quantum computers have grown more powerful, researchers have devised increasingly sophisticated ways to test whether these machines are truly harnessing quantum effects—but every method so far has run into limits.
In new research published in Nature Communications, a team led by computer scientists Marcello Benedetti and Harry Buhrman at Quantinuum in the U.K. has proposed a new kind of test built around a simple game with a mathematically guaranteed outcome.
Fast radio bursts could help disentangle galactic feedback from dark matter effects
Intense, brief flashes of radio light called fast radio bursts (FRBs) travel across billions of light-years to reach Earth, passing through a fog of matter along the way. The bursts’ origins are unclear but may originate from highly magnetized dead stars called magnetars. The denser the fog through which FRBs travel, the more dispersed their signals become—similar to the way a prism splits white light into a rainbow of colors.
Thanks to this dispersive property, FRBs make excellent tracers of how ordinary matter is distributed in the universe; ordinary matter is the same stuff that makes up people, planets, stars and anything made of subatomic particles called baryons. As the FRB radio beams pass through this matter in our universe, they can essentially map out how much is present and how clumpy it is.
In a new Nature Astronomy study, researchers show how these FRB measurements can help solve some of the biggest questions in cosmology.
Memristor chip breaks the capacity limit of brain-inspired associative memory
Researchers in the Department of Electrical and Computer Engineering of the Faculty of Engineering and the Centre for Advanced Semiconductors and Integrated Circuits (CASIC) at the University of Hong Kong (HKU) have made a breakthrough in brain-inspired computing. In collaboration with Hewlett Packard Labs, the team has developed a memristor chip that overcomes a long-standing limit on the capacity of “associative memory,” the brain-like ability to recall complete information from a partial cue, while keeping it reliable even when a large fraction of the hardware fails.
Associative memory is something the brain does effortlessly: A few notes bring a whole song to mind, and a glimpse of a face identifies a person. Unlike the RAM in a computer, which must be told exactly where information is stored, associative memory retrieves it by content—the very capability that pattern completion, error correction and recognition depend on.
Invention may bring smart bionic eye into sight
A working prototype that can see, remember and interact with the world like the human brain could one day underpin smart bionic eyes while using far less energy than today’s technologies. The invention from RMIT University combines sensing, memory and information processing within the same system, reducing the need to constantly move data between separate sensors, memory banks and processors.
While still an early-stage research demonstration, the neuromorphic vision innovation could dramatically reduce the amount of data and energy required to perform complex visual tasks.
RMIT has an international patent application filed under the Patent Cooperation Treaty (PCT) for the invention.
Curved nanographene with five-, six- and seven-membered rings synthesized in two steps
Nanographenes can be considered molecular fragments of graphene, a 2D conductive material in which carbon atoms are connected in a honeycomb pattern. Because their electronic and photophysical properties vary depending on the size and shape of the molecule, nanographenes are expected to find applications in OLEDs, organic solar cells, organic field-effect transistors and more.
For this, simple methods for synthesizing nanographenes that avoid complex multistep processes are desired. Now, a team of scientists from WPI-ITbM at Nagoya University and RIKEN has established a new two-step annulative π-extension (APEX) method that generates structurally diverse nanographenes. This research is published in the journal Angewandte Chemie International Edition.
New molecular magnet design boosts performance for ultrahigh-density data storage
Researchers at The University of Manchester and the Australian National University have developed a new class of molecular magnets that combines the most successful features of previous designs, resulting in some of the strongest magnetic memory properties reported to date.
The work, published in Nature Communications, centers on single-molecule magnets (SMMs), a class of materials capable of storing magnetic information within individual molecules. These materials are being explored as candidates for future ultrahigh-density data storage technologies, as they offer the potential for information to be stored on a dramatically smaller scale than in conventional magnetic devices.
Controlling the geometry of lanthanide compounds has long been one of the major challenges in molecular magnet design. The researchers have overcome part of that challenge by combining two molecular architectures that had previously delivered strong, but different, magnetic properties.
Tiny molecular rings open new ways for designing better medicines
Cyclopropanes are organic chemistry’s smallest rings. Three carbon atoms are joined in a triangle, creating a compact and unusually strained structure. Despite—or partly because of—this unusual geometry, cyclopropanes are found in many biologically active natural products and have important applications in medicines and drug discovery, from antidepressants to antibiotics and antiviral research.
Connect these carbon triangles to an amine, a functional group with a nitrogen at its center, and you get aminocyclopropanes. They are of particular interest in pharmaceutical research because they can be used to replace another substructure commonly found in drug molecules: α,α-gem-dimethylamines (compounds in which the aminocyclopropane’s triangle is “opened” by disconnecting one edge).
Such molecular substitutes that resemble an existing part of a drug but can alter important properties, such as biological activity and metabolic stability, are referred to as bioisosteres and have shown beneficial effects in countless cases.