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Category: particle physics

Probing the existence of a fifth force via neutron star cooling

Neutron stars are ultra-dense star remnants made up primarily of nucleons (i.e., protons and neutrons). Over the course of millions of years, these stars progressively cool down, radiating heat into space.

The cooling process of neutron stars could be a promising testbed for various hypothetical particles, including so-called scalar particles. These are particles that do not possess a spin and that, according to some theoretical predictions, could couple to nucleons.

Scalar particles are hypothesized to violate two fundamental laws of gravity, known as the equivalence principle and the inverse-square law. Their observation could thus greatly enrich the present understanding of the universe and its underlying physical forces.

Rydberg-atom detector conquers a new spectral frontier

A team from the Faculty of Physics and the Center for Quantum Optica l Technologies at the Center of New Technologies, University of Warsaw has developed a new method for measuring elusive terahertz signals using a “quantum antenna.”

The authors of the work utilized a novel setup for radio wave detection with Rydberg atoms to not only detect but also precisely calibrate a so-called frequency comb in the terahertz band. This band was until recently a white spot in the electromagnetic spectrum, and the solution described in the journal Optica paves the way for ultrasensitive spectroscopy and a new generation of quantum sensors operating at room temperature.

Terahertz (THz) radiation, being part of the electromagnetic spectrum, lies at the boundary of electronics and optics, positioned between microwaves (used, for example, in Wi-Fi) and infrared.

Quantum Computer Recycles Its Atomic Qubits

Trapped neutral atoms are an attractive platform for quantum computing, as large arrays of atomic qubits can be arranged and manipulated to perform gate operations. However, the loss of useable atoms—either from escape or from disturbance—can be a limitation for long computations with repeated measurements. Researchers at Atom Computing, a company in California, have devised a “reset or reload” protocol that mitigates atom losses [1]. The method was successfully employed during a computation consisting of 41 cycles of qubit measurements.

All current quantum computers require error correction, which involves measuring certain qubits at intermediate steps of a computation. Reusing these qubits would avoid needing a prohibitively high overhead in qubit numbers, says team member Matthew Norcia. But in the case of atoms, the process of resetting measured qubits risks disturbing unmeasured ones.

To overcome this challenge, the researchers have developed a way to shield unmeasured atoms from the resetting process. They use targeted laser beams to immunize the unmeasured atoms against excitation by shifting their resonances. They then turn on a second set of lasers that cool the measured atoms and reinitialize them, enabling them to join the unmeasured atoms in the next computational step.

Moisture-driven power generator delivers stable electricity even in dry air conditions

Their findings have been published in the journal Advanced Functional Materials in an article titled “Long-Lasting Moisture Energy Scavenging in Dry Ambient Air Empowered by a Salt Concentration-Gradient Cationic Hydrogel.”

How the new MEG technology works These moisture-activated generators (or MEGs) work by creating a flow of ions—charged particles—inside a special gel, generating power naturally. But current versions face challenges: they don’t last long (less than 16 hours), have high internal resistance, and only work well in very humid conditions.

Professor Shin and his team have overcome those hurdles. They developed a salt-concentration-gradient cationic hydrogel for MEG, promising lower energy loss and higher output even in conditions of low relative humidity.

Most normal matter in the universe isn’t found in planets, stars or galaxies: An astronomer explains

If you look across space with a telescope, you’ll see countless galaxies, most of which host large central black holes, billions of stars and their attendant planets. The universe teems with huge, spectacular objects, and it might seem like these massive objects should hold most of the universe’s matter.

But the Big Bang theory predicts that about 5% of the universe’s contents should be atoms made of protons, neutrons and electrons. Most of those atoms cannot be found in stars and galaxies—a discrepancy that has puzzled astronomers.

If not in visible stars and galaxies, the most likely hiding place for the matter is in the dark space between galaxies. While space is often referred to as a vacuum, it isn’t completely empty. Individual particles and atoms are dispersed throughout the space between stars and galaxies, forming a dark, filamentary network called the “cosmic web.”

Earlier ultra-relativistic freeze-out could revive a decades-old theory for dark matter

A new theory for the origins of dark matter suggests that fast-moving, neutrino-like dark particles could have decoupled from Standard Model particles far earlier than previous theories had suggested.

Through new research published in Physical Review Letters, a team led by Stephen Henrich and Keith Olive at the University of Minnesota proposes that this “ultra-relativistic freeze-out” mechanism could have produced dark matter particles which are almost undetectable, but still compatible with the observed history of the universe.

Despite comprising some 85% of the universe’s total mass, dark matter has never been seen to interact with regular matter except via gravity, making its origins one of the most enduring mysteries in cosmology.

CERN’s ATLAS detects evidence for decay of Higgs boson into muon–antimuon pair

Although its existence had been theorized for decades, the Higgs boson was finally observed to exist in 2012 at the Large Hadron Collider (LHC) at CERN. Since then, it has continued to be heavily studied at the LHC. Now, a new study from the researchers at CERN combines the last two runs of ATLAS—one of the two general-purpose detectors at the LHC—to lay out evidence that the Higgs boson can decay into a muon–antimuon pair.

The study, published in Physical Review Letters, reports a significance of 3.4 standard deviations of excess signal over background, when the two runs are combined—higher than previous evidence from the Compact Muon Solenoid (CMS) of 3.0 standard deviations.

A solid-state quantum processor based on nuclear spins

Quantum computers, systems that process information leveraging quantum mechanical effects, have the potential of outperforming classical systems on some tasks. Instead of storing information as bits, like classical computers, they rely on so-called qubits, units of information that can simultaneously exist in superpositions of 0 and 1.

Researchers at University Paris-Saclay, the Chinese University of Hong Kong and other institutes have developed a new quantum computing platform that utilizes the intrinsic angular momentum (i.e., spin) of nuclei in tungsten-183 (183 W) atoms as qubits.

Their proposed system, introduced in a paper published in Nature Physics, was found to achieve long coherence times and is compatible with existing superconductor-based quantum information processing platforms.

LHC data confirm validity of new model of hadron production—and test foundations of quantum mechanics

A boiling sea of quarks and gluons, including virtual ones—this is how we can imagine the main phase of high-energy proton collisions. It would seem that particles here have significantly more opportunities to evolve than when less numerous and much “better-behaved” secondary particles spread out from the collision point. However, data from the LHC accelerator prove that reality works differently, in a manner that is better described by an improved model of proton collisions.

A lot happens during high-energy proton-proton collisions. Protons are hadrons, i.e. clusters of partons—quarks and the gluons that bind them together. When protons collide with each other at sufficiently high energies, their quarks and gluons (including the virtual ones, which appear momentarily during interactions) enter into various complex interactions.

Only when they “cool down” do the quarks stick together to form new hadrons, which scatter from the collision area and are recorded in detectors. Intuition therefore suggests that the entropy of the produced hadrons—a quantity describing the number of states in which the particle system can find itself—should be different from that in the parton phase of the collision, when there are many interacting quarks and gluons, and the interactions appear at first glance to be as chaotic as they are dynamic.

CMS gets acquainted with a family of all-charm tetraquarks

Upon close inspection, the tetraquark family members are consistent with tightly bound diquark pairs

The CMS Collaboration has identified three extremely rare same-flavor teraquark states and determined, based on their spin-parity configuration, that they are consistent with a diquark-antidiquark model.

In recent years, a long-standing orthodoxy that all strongly interacting particles (hadrons) are either pairs (mesons) or triplets (baryons) of quarks (q) has been fundamentally overturned. Rapid progress has been made in identifying a plethora of candidates for “exotic hadrons”, including tetraquarks (qq̅qq̅) and pentaquarks (qqqqq̅), now recognized within the scientific community.

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