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Physicists bring unruly molecules to the quantum party

Scientists have made leaps and bounds in bending atoms to their will, making them into everything from ultraprecise clocks to bits of quantum data. Translating these quantum technologies from obedient atoms to unruly molecules could offer greater possibilities. Molecules can rotate and vibrate. That makes molecules more sensitive to certain changes in the environment, like temperature.

“If you’re sensitive to something, it can be a curse, because you would like to not be sensitive, or it can be a blessing,” said NIST physicist Dietrich Leibfried. “You can use that sensitivity to your advantage.”

But that same sensitivity has made molecules difficult to control. Recently, physicists at the National Institute of Standards and Technology (NIST) achieved new levels of control over molecules. In a study published in Physical Review Letters, they were able to manipulate a calcium hydride molecular ion—made up of one atom of hydrogen and one atom of calcium, with one electron removed to make it a charged molecule—with almost perfect success. And this control opens possibilities for quantum technology, chemical research and exploring new physics.

Comet 3I/ATLAS: Europa Clipper captures rare ultraviolet view

The Southwest Research Institute-led Ultraviolet Spectrograph (UVS) aboard NASA’s Europa Clipper spacecraft has made valuable observations of the interstellar comet 3I/ATLAS, which in July became the third officially recognized interstellar object to cross into our solar system. UVS had a unique view of the object during a period when Mars- and Earth-based observations were impractical or impossible.

A simple spin swap reveals exotic anyons

Researchers from the University of Innsbruck, the Collège de France, and the Université Libre de Bruxelles have developed a simple yet powerful method to reveal anyons—exotic quantum particles that are neither bosons nor fermions—in one-dimensional systems. Their paper is published in Physical Review Letters.

In conventional three-dimensional space, particles belong to one of two categories: fermions or bosons. In low-dimensional settings, however, quantum mechanics allows for more exotic behavior. Here, anyons can emerge—quasi-particles whose exchange properties continuously interpolate between those of bosons and fermions, leading to fractional statistics. Detecting and engineering such particles in one dimension has long been a central challenge, typically requiring, as theory proposals suggest, intricate scattering schemes or density-dependent tunneling processes.

The new study by teams led by Hanns-Christoph Nägerl at the University of Innsbruck and Nathan Goldman at the Université Libre de Bruxelles and Collège de France (CNRS) now introduces a remarkably simple yet powerful approach. The researchers propose an effective “swap” model that leverages the spin degree of freedom of ultracold atoms. By assigning a complex phase to the exchange—or “swap”—of two spins, the system naturally acquires the fractional statistical behavior characteristic of anyons.

Bazinga! Physicists crack a ‘Big Bang Theory’ problem that could help explain dark matter

A professor at the University of Cincinnati and his colleagues have figured out something two of America’s most famous fictional physicists couldn’t: how to theoretically produce subatomic particles called axions in fusion reactors.

Particle physicists Sheldon Cooper and Leonard Hofstadter, roommates in the sitcom “The Big Bang Theory,” worked on the problem in three episodes of Season 5, but couldn’t crack it.

Now UC physics Professor Jure Zupan and his theoretical physicist co-authors at the Fermi National Laboratory, MIT and Technion–Israel Institute of Technology think they have one solution in a study published in the Journal of High Energy Physics.

Silicon atom processor links 11 qubits with more than 99% fidelity

In order to scale quantum computers, more qubits must be added and interconnected. However, prior attempts to do this have resulted in a loss of connection quality, or fidelity. But, a new study published in Nature details the design of a new kind of processor that overcomes this problem. The processor, developed by the company Silicon Quantum Computing, uses silicon—the main material used in classical computers—along with phosphorus atoms to link 11 qubits.

The new design uses precision-placed phosphorus atoms in isotopically purified silicon-28, which are arranged into two multi-nuclear spin registers. One register contains four phosphorus atoms, while the other contains five, and each register shares an electron spin. The two registers are linked by electron exchange interaction, allowing for non-local connectivity across the registers and 11 linked qubits.

Because of the placement of silicon and phosphorus in the periodic table, the design is referred to as the “14|15 platform.” This 11-qubit atom processor in silicon is the largest of its kind to date, marking a major accomplishment for quantum computing.

Scientists build a quantum computer that can repair itself using recycled atoms

Like their conventional counterparts, quantum computers can also break down. They can sometimes lose the atoms they manipulate to function, which can stop calculations dead in their tracks. But scientists at the US-based firm Atom Computing have demonstrated a solution that allows a quantum computer to repair itself while it’s still running.

The team zeroed in on quantum computers that use neutral atoms (atoms with equal numbers of protons and electrons). These individual atoms are the qubits, or the basic building blocks of a quantum computer’s memory. They are held in place by laser beams called optical tweezers, but the setup is not foolproof.

Occasionally, an atom slips out of its trap and disappears. When this happens mid-calculation, the whole process can grind to a halt because the computer can’t function with a missing part.

Elegant solution for measuring ultrashort laser pulses discovered

Ultrashort laser pulses—that are shorter than a millionth of a millionth of a second—have transformed fundamental science, engineering and medicine. Despite this, their ultrashort duration has made them elusive and difficult to measure.

About 10 years ago, researchers from Lund University and Porto University introduced a tool for measuring pulse duration of ultrafast lasers. The same team has now achieved a breakthrough that enables the measurement of individual laser pulses across a wider parameter range in a more compact setup.

“The current standard measurements for femtosecond lasers, typically used in industry and medicine, give just an estimate of the pulse duration. Our approach gives a more complete measurement and can contribute to unleashing the whole potential of ultrafast laser technology,” says Daniel Díaz Rivas, doctoral student in Atomic Physics at Lund University.

Flat Fermi surface in altermagnets enables quantum limit spin currents

The key feature of spintronic devices is their ability to use spin currents to transfer momentum, enabling low-energy, high-speed storage and logical signal control. These devices are usually manipulated by electric currents and fields. The charge-to-spin conversion efficiency (CSE) is a key metric for evaluating their performance.

Now, scientists from the Institute of Metal Research (IMR) of the Chinese Academy of Sciences have proposed a new deep correlation between the spin splitting torque (SST) and the Fermi surface geometry, achieving a quantum limit of 100% in a system with a flat Fermi surface. These results were published in Physical Review Letters on December 16.

Super strain-resistant superconductors

Superconductors are materials that can conduct electricity with zero resistance, usually only at very low temperatures. Most superconductors behave according to well-established rules, but strontium ruthenate, Sr₂RuO₄, has defied clear understanding since its superconducting properties were discovered in 1994. It is considered one of the cleanest and best-studied unconventional superconductors, yet scientists still debate the precise structure and symmetry of the electron pairing that gives rise to its remarkable properties.

One powerful way to identify the underlying superconducting state is to measure how the superconducting transition temperature, or Tc, changes under strain, since different superconducting states respond differently when a crystal is stretched, compressed, or twisted.

Many earlier experiments, especially ultrasound studies, suggested that Sr₂RuO₄ might host a two-component superconducting state, a more complex form of superconductivity that can support exotic behaviors such as internal magnetic fields or multiple coexisting superconducting domains. But a genuine two-component state is expected to respond strongly to shear strain.

Physicists Propose First-Ever Experiment To Manipulate Gravitational Waves

When massive cosmic objects such as black holes merge or neutron stars crash into one another, they can produce gravitational waves. These ripples move through the universe at the speed of light and create extremely small changes in the structure of space-time. Their existence was first predicted by Albert Einstein, and scientists confirmed them experimentally for the first time in 2015.

Building on this discovery, Prof. Ralf Schützhold, a theoretical physicist at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), is proposing a bold new step.

Schützhold has developed a concept for an experiment that would go beyond detecting gravitational waves and instead allow researchers to influence them. The proposal, published in the journal Physical Review Letters, could also help clarify whether gravity follows quantum rules, a question that remains unresolved in modern physics.

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