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Category: particle physics

Scientists identify the origin of noise in spin qubit quantum processors

A spin qubit, in which quantum information is encoded in the spin state of an electron, is one of the most promising platforms for quantum computing. Spin qubits exhibit long coherence times and are compatible with advanced semiconductor manufacturing technologies. The leading implementation of spin qubits involves confined electrons inside quantum dots, a nanoscale semiconductor architecture that behaves like a controllable artificial atom. Recent advances have enabled high-fidelity operation of single- and two-qubit gates, exceeding the threshold required for certain surface code quantum error correction techniques.

Physicists create new family of Schrödinger-cat states

Quantum mechanics, unlike classical physics, allows objects to exist in more than one state at the same time. This idea is often illustrated by Schrödinger’s cat, imagined as being both alive and dead until it is observed. In the laboratory, physicists can create less dramatic but very real versions of this effect by placing atoms, light or motion into two distinct quantum states at once. Creating and controlling these superpositions is essential for applications ranging from quantum computing to precision timekeeping.

A simple example is a quantum bit, or qubit, in a superposition of both 0 and 1. But quantum systems are not limited to just two states. In a quantum harmonic oscillator, which can occupy many different energy levels, there is a much richer set of possibilities. Quantum harmonic oscillators describe many physical systems, including light, vibrations and the motion of trapped particles, and have been used to create a wide variety of quantum superpositions. One well-known example is a “cat state,” in which an oscillator is placed in a superposition of two wave packets displaced in opposite directions. These wave packets, known as coherent states, resemble classical motion as closely as quantum mechanics allows.

Researchers at the University of Oxford have now demonstrated a new family of quantum superpositions. Instead of building catlike states from coherent-state wave packets, they developed a method for creating superpositions from a broad range of components that are themselves highly nonclassical. In examples such as squeezed-state superpositions, quantum uncertainty is redistributed differently in each part of the state. The research is published in the journal Physical Review X.

Tabletop experiment helps reconcile fundamental physics

Assistant Professor Haocun Yu is something of a scientific diplomat. In a recent Physical Review Letters publication, she and her colleagues show how a tabletop experiment can bring together two bedrock physics theories that have never been fully reconciled.

More than a century ago, Albert Einstein gave us the theory of general relativity, describing gravity in relation to space and time on a large scale. Within a decade, physicists were developing a deeper knowledge of quantum mechanics, the laws that govern the subatomic world, including atoms, photons and other microscopic systems.

“Quantum mechanics and general relativity are two of the most successful theories in physics, but they describe nature in very different ways,” Yu explained.

Research uncovers novel electronic properties in quantum material

Florida State University physicists are part of a team that has discovered unusual superconducting states in parts of graphene, with the potential to drive unexpected quantum technologies.

Assistant Professor of Physics Cyprian Lewandowski and postdoctoral researcher Phong Võ Tiến are part of an international collaboration that has uncovered new aspects of superconductivity and topology in rhombohedral graphene, a system comprising just a few layers of carbon atoms stacked like the treads of a staircase in a shape known as chiral stacking. The work is published in Nature Physics.

“The rhombohedral graphene system seems to capture many of the intriguing electronic phenomena that scientists have seen previously in other atomically thin systems, but they were previously not as ideal for technical applications because of the intrinsic complexity of the devices or replicability issues,” Lewandowski said.

Achiral crystal reveals Raman optical activity through ferroaxial order

Raman optical activity, long thought to require chiral molecules or magnetic order, has been demonstrated in an achiral, nonmagnetic crystal by researchers at the Institute of Science Tokyo. The effect arises through ferroaxial order, a coordinated rotation of atoms within the lattice, and is detected using circularly polarized Raman spectroscopy. The findings show that optically inactive materials can also display chirality-like optical responses and expand the scope of optical techniques for discovering new materials.

In nature, molecules can be divided into two categories based on their symmetry: chiral and achiral. Chiral molecules are not identical to their mirror images, much like left and right hands. Achiral molecules, by contrast, are identical to their mirror images and therefore do not possess a definite handedness.

Light offers a way to distinguish between these two types. When light interacts with a chiral molecule, the response depends on its handedness. For example, chiral molecules absorb left-and right-circularly polarized light to different extents, a phenomenon known as circular dichroism. They also scatter these two types of light with different intensities, an effect called Raman optical activity (ROA), which is widely used to identify chirality. ROA has long been associated only with chiral molecules or with materials that have magnetic order, where inversion or time-reversal symmetry is broken.

Scientists may have found the source of the most powerful neutrino ever detected

A record-shattering particle from deep space may have exposed some of the universe’s most extreme black hole engines. A mysterious particle from deep space has scientists buzzing after the most energetic neutrino ever detected slammed through the Mediterranean Sea. Now, researchers think they may have identified the cosmic “culprits” behind it: blazars — supermassive black holes blasting jets of matter straight toward Earth.

Three years ago, scientists detected something extraordinary deep beneath the Mediterranean Sea: the most energetic cosmic neutrino ever observed. The particle carried an astonishing energy of around 220 PeV, more than ten times greater than previously detected high energy neutrinos, and researchers still do not know exactly where it came from.

Now, a new study published in the Journal of Cosmology and Astroparticle Physics (JCAP) suggests the particle may have originated from blazars, some of the universe’s most extreme objects. Blazars are active galactic nuclei powered by supermassive black holes that shoot enormous jets of plasma directly toward Earth.

New light-based switch could cut chip energy use and speed future AI photonics

2D nanocavity exciton polaritons. (a) Schematic of the coupled TMD-PhC nanocavity. (b) Schematic of the gate-tunable TMD stack. © Scanning electron microscope image of the suspended Si3N4 nanobeam cavity, with the inset showing the simulated cavity mode profile. The dark area is suspended from the SiO2 substrate. Scale bar, 500 nm. Credit: Physical Review Letters (2026). DOI: 10.1103/gc15-qsvf.

Photonic devices are hardware systems that can process information using light instead of electricity. These systems could potentially perform computations faster than electronic devices, while also consuming less energy.

A key challenge faced by engineers developing photonic systems is achieving strong optical nonlinearities, or in other words, developing approaches that enable the control of light signals using light, all while consuming little power. A proposed solution to attain these light-light interactions entails the use of exciton polaritons, hybrid particles that are formed when photons couple with excitons (i.e., bound pairs of electrons and holes inside semiconductors).

Critical Te-104 decay measurements may help answer century-old alpha particle formation question

University of Tennessee, Knoxville physicists and their colleagues have made critical measurements of the lifetime and decay energy of tellurium-104 (Te-104), an important step in answering a century-old question and understanding how hundreds of nuclei decay. The results are published in Nature.

Professor Robert Grzywacz led the experimental team at the Radioactive Isotope Beam Factory (RIBF) at RIKEN in Japan. He explained how the results match decades-old predictions that tellurium-104 is a special case in alpha decay, a process where an alpha particle (a strongly bound system of two protons and two neutrons) tunnels through the barrier surrounding the nucleus where it resides. Though alpha radioactivity was discovered more than 125 years ago, where the particle comes from is still a mystery, especially in nuclei that have large numbers of protons and neutrons.

“Alpha decay is the oldest decay mode,” Grzywacz said. “The big question is how the alpha particle forms in heavy nuclei, which are known to have uniform matter distribution. There must be a mechanism which causes local ‘clump’ or ‘cluster’ formation.”

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