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Category: particle physics – Page 26

Quantum semiconductor design could expand search for dark matter

Dark matter accounts for 85% of the matter in the universe, but scientists still do not know what it is made of. A study, published in Physical Review Letters, by Rice University researchers proposes a detector design that could help search for axions, hypothetical particles that many physicists think could make up dark matter.

The proposed detector would rely on a class of semiconductor materials whose response changes when their orientation shifts within a magnetic field. This material response makes it easier to tune the detector, allowing researchers to probe a range of axion masses that have remained difficult to explore with existing technologies.

“We are proposing a well-studied material from condensed matter physics for a new application—axion detection,” said Jaanita Mehrani, a doctoral student in Rice’s Applied Physics Graduate Program who is the first author on the study. “What’s different about this material is that it doesn’t have to use complex mechanical tuning mechanisms, it simply tunes with the magnetic field.”

Quantum gravity tests may mistake ordinary spacetime for superposition

Everything around us, from atoms and molecules to planets and galaxies, is governed by two extraordinarily successful theories of physics: quantum mechanics and gravity. Quantum mechanics explains the behavior of the microscopic world, while Einstein’s theory of gravity describes the motion of stars, black holes and the expansion of the universe. Yet despite their successes, physicists are still searching for a theory of “quantum gravity” that would unite them into a single description of nature.

One of the most widely expected features of such a theory is that gravity should obey the laws of quantum mechanics. And this is where it gets difficult: Quantum mechanics predicts that any object can be delocalized over multiple places at once, which is routinely tested in experiments with atoms and even small clumps of metal. Gravity, according to Einstein’s theory, is space and time itself—it can be curved, flat or even have waves propagating through it, as confirmed by gravitational wave detectors. So many physicists believe that spacetime around a quantum object would also exist in multiple “states” simultaneously.

But what would such a situation actually look like?

Quantum computer simulates hadronization, reproducing string breaking with 104 qubits

By remotely accessing an IBM quantum computer, a research scientist at Lawrence Berkeley National Laboratory has successfully simulated a key process in particle physics: hadronization. Although based on a simplified model of quantum mechanics, the project lays the groundwork for how physicists can leverage the power of quantum computers to make large scientific calculations beyond the capabilities of classical supercomputers. The research is published in the journal Physical Review D.

Hadronization occurs when two or more quarks—the subatomic building blocks of matter—bind together through the strong nuclear force to form composite particles called hadrons. The most familiar examples of hadrons are protons and neutrons, which form the nuclei of atoms. So, having a better understanding of the hadronization process means having a better understanding of the structure of matter, and—in turn—the universe.

Physical experiments have not been able to reveal every step of the process, however. Researchers at the Large Hadron Collider (LHC) at CERN accelerate protons to near light speeds, guide them into collisions and study the resulting debris of quarks and antiquarks. But these particles can only be indirectly measured before they immediately undergo hadronization—hence the need for computer simulations to fill in the gaps of these scientific observations.

Physicists demonstrate Hong–Ou–Mandel interference with more than 10 atoms

In a new study published in Nature Physics, researchers have demonstrated the Hong–Ou–Mandel (HOM) effect with up to 12 indistinguishable neutral atoms—an effect that has been predominantly observed in photonic systems.

The Hong–Ou–Mandel effect is a quantum phenomenon rooted in particle indistinguishability. When two identical bosons meet at a 50:50 beam splitter, they always exit together through the same output port. In other words, they “bunch up.” A single particle at each output is never found, even though that is the statistically expected outcome if the beam splitter were simply distributing particles at random.

First observed with pairs of photons in 1987, the HOM effect has since become central to quantum information and quantum metrology. For two particles, the physics is well established. However, extending it to many particles is a different challenge.

First-of-a-kind laser spring opens up new avenues for plasma control

When a high-intensity laser interacts with plasma, the charged particles typically oscillate back and forth like waves on the ocean. But what if the laser itself could twist like a whirlpool? Researchers have now demonstrated a rotating, spring-shaped laser pulse, opening new possibilities for fusion energy, particle acceleration, astrophysics and beyond.

In new research published in Nature Photonics, scientists from Lawrence Livermore National Laboratory (LLNL) and the University of California, Irvine, demonstrated the first high-intensity “light spring” laser.

Unlike conventional laser beams, a light spring rotates around its central axis at a controllable rate. If shone onto a wall, the beam pattern would trace out circles over time.

Disorder creates direction-dependent optics in compound semiconductors

An international research team has demonstrated that the intrinsic disorder of the compound semiconductor CuInSnS₄ can be exploited to influence its optical properties. While the atomic vibrations also sense the local disorder, their response is averaged over many different local environments and therefore appears isotropic, as expected for a cubic crystal.

In contrast, the optical excitations, known as excitons, are much more sensitive to the local arrangement of atoms. Surprisingly, they show a direction-dependent optical response even though the average crystal structure is cubic. These findings shed new light on the relationship between disorder and material properties, opening new options for targeted “disorder engineering” in optoelectronic and photocatalytic devices.

Crystals are typically characterized by a periodic arrangement of atoms, in which each element occupies well-defined crystallographic sites throughout the structure. In compound semiconductors such as CuInSnS₄, a member of the adamantine chalcogenide family, the cations are ideally distributed over specific positions in the crystal structure.

World’s largest particle smasher halts for upgrade to boost hunt for dark matter

The world’s most powerful particle accelerator will shutter operations Monday for four years of renovations to dramatically boost its collision capacity and the potential for unlocking one of the greatest mysteries of the universe: dark matter.

The Large Hadron Collider (LHC)—a 27-kilometer (17-mile) proton-smashing circular tunnel at the heart of Europe’s physics lab CERN near Geneva—has most famously been used to prove the existence of the Higgs boson, dubbed “the God particle.”

In the tunnel, running about 100 meters (330 feet) below the French-Swiss border area, superconducting magnets and accelerating structures propel particles to extreme energies and then smash them together at phenomenal speeds.

Graphene can hold multiple states of superconductivity, a new study finds

The researchers discovered the multiple superconducting states in atomically thin exfoliations of graphite, known as graphene. Specifically, graphene is a single-atom-thin sheet of carbon atoms arranged precisely in a microscopic lattice. The team made its discoveries in samples of rhombohedral graphene, which is a natural structure within graphite consisting of a stack of four or five graphene layers.

Interestingly, the researchers found that several of the new superconducting states in rhombohedral graphene are able to persist in the presence of a magnetic field, which normally kills superconductivity.

And in a further surprise, these superconducting states even get stronger when exposed to a magnetic field.

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