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Category: particle physics

Paul M. Sutter is an astrophysicist at The Ohio State University, host of Ask a Spaceman and Space Radio, and author of “Your Place in the Universe.” Sutter contributed this article to Space.com’s Expert Voices: Op-Ed & Insights.

Is it a wave, or is it a particle? This seems like a very simple question. Waves are very distinct phenomena in our universe, as are particles. And we have different sets of mathematics to describe each of them. So, if we want to go about describing the entire universe, this appears to be a very handy classification scheme — except when it isn’t. And it isn’t in one of the most important aspects of our universe: the subatomic world.

When it comes to things like photons and electrons, the answer to the question “Do they behave like waves or particles?” is … yes.

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In years to come, quantum computers and quantum networks might be able to tackle tasks that are inaccessible to traditional computer systems. For instance, they could be used to simulate complex matter or enable fundamentally secure communications.

The elementary building blocks of quantum information systems are known as qubits. For to become a tangible reality, researchers will need to identify strategies to control many qubits with very high precision rates.

Spins of individual particles in solids, such as electrons and nuclei have recently shown great promise for the development of quantum networks. While some researchers were able to demonstrate an elementary control of these qubits, so far, no one has reported entangled quantum states containing more than three spins.

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A team of researchers from the U.K., China and Spain has found that graphene exhibits mechanical properties that are similar to those of graphite. In their paper published in the journal Physical Review Letters, the group describes testing flakes of graphene in a unique way, and what they found.

Graphene is a sheet of carbon atoms just a single atom thick, sometimes called a two-dimensional material. In this new effort, the researchers questioned whether it truly is a by testing it to see if it has 3D mechanical properties.

Prior research has shown that graphene does behave as a 2-D material when looking at its . It also behaves like a 2-D material when testing its thermal properties. But until now, its mechanical properties had not been tested. The reason fis that graphene falls apart nearly instantly when not supported by a substrate, presenting difficulties in testing its mechanical properties without also including those of the substrate. To get around this problem, the researchers tested one of graphene’s by suspending graphene flakes in a viscous liquid, thereby preventing phonons from shaking it apart. The liquid also prevented the flakes from bonding and forming graphite. The team then carried out a common 3D test—applying , in this case, using a diamond anvil cell. Doing so showed (via Raman spectroscopy) that the energy shift that resulted from its phonons was closer to that exhibited by a 3D material (graphite) than a 2-D material.

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A team of researchers affiliated with several institutions in France has observed a phase transition in an artificially created flock. In their paper published in the journal Physical Review Letters, the group describes how they created their artificial flock and the events that led to a phase transition.

Scientists trying to understand generally create computer models meant to mimic under crowded conditions—but such simulations are limited by the parameters that are used to create them. Most in the field agree on the need to recreate or flocking behavior physically in a lab. In this new effort, the researchers have built on prior work with an artificial crowd, and have found that under certain conditions it underwent a phase transition similar to water freezing to an ice state.

Working on a prior effort, some of the team members created an artificial crowd consisting of millions of suspended in a liquid between two plates of glass. The plates were joined in a way that allowed the beads to move around the outer edges of an oval—similar to cars on a partially three-dimensional race track. The beads were forced to move in one direction by applying an —the Quincke effect spun the beads, which pushed them through the liquid in the same direction. Also, due to a dipole effect, the beads did not adhere to one another—instead, they moved around the track, seemingly of their own accord. The prior team showed that increasing density of the beads could set off a Vicsek-like transition in which randomly moving particles exhibit flock-like behaviors. In this new effort, the researchers used the same setup with the beads to create a flock and then watched what would happen as density was increased.

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Hidden deep in a basement at Stanford stands a 10-meter-tall tube, wrapped in a metal cage and draped in wires. A barrier separates it from the main room, beyond which the cylinder spans three stories to an apparatus holding ultra-cold atoms ready to shoot upward. Tables stocked with lasers to fire at the atoms—and analyze how they respond to forces such as gravity—fill the rest of the laboratory.

The tube is an , a custom-built device designed to study the wave nature of . According to quantum mechanics, atoms exist simultaneously as particles and waves. The Stanford instrument represents a model for an ambitious new instrument ten times its size that could be deployed to detect gravitational waves—minute ripples in spacetime created by energy dissipating from moving astronomical objects. The instrument also could shed light on another mystery of the universe: dark matter.

Stanford experimental physicists Jason Hogan and Mark Kasevich never intended for their device to be implemented this way. When Hogan began his graduate studies in Kasevich’s lab, he focused instead on testing gravity’s effects on atoms. But conversations with theoretical physicist Savas Dimopoulos, a professor of physics, and his graduate students—often lured downstairs by an espresso machine housed directly across the hall from Kasevich’s office—led them to start thinking about its utility as a highly .

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Linear algebra is a field of mathematics that has been thoroughly investigated for many centuries, providing invaluable tools used not only in mathematics, but also across physics and engineering as well as many other fields. For years physicists have used important theorems in linear algebra to quickly calculate solutions to the most complicated problems.

This August, three theoretical physicists—Peter Denton, a scientist at Brookhaven National Laboratory and a scholar at Fermilab’s Neutrino Physics Center; Stephen Parke, at Fermilab; and Xining Zhang, a University of Chicago graduate student working under Parke—turned the tables and, in the context of particle physics, discovered a fundamental in .

The identity relates eigenvectors and eigenvalues in a direct way that hadn’t been previously recognized. Eigenvectors and eigenvalues are two important ways of reducing the properties of a matrix to their most basic components and have applications in many math, physics and real-world contexts, such as in analyzing vibrating systems and facial recognition programs. The eigenvectors identify the directions in which a transformation occurs, and the eigenvalues specify the amount of stretching or compressing that occurs.

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Are there new, unknown particles that can explain dark matter and other mysteries of the universe? To try to answer this question, particle physicists typically sift through the myriad of particles that are produced in particle collisions. But they also have an indirect but powerful way of looking for new particles, which is to measure processes that are both rare and precisely predicted by the Standard Model of particle physics. A slight discrepancy between the Standard Model prediction and a high-precision measurement would be a sign of new particles or phenomena never before observed.

One such process is the transformation, or “decay”, of a positively charged variant of a particle known as kaon into a positively charged pion and a neutrino–antineutrino pair. In a seminar that took place today at CERN, the NA62 collaboration reported two potential instances of this ultra-rare kaon decay. The result, first presented at the International Conference on Kaon Physics, shows the experiment’s potential to make a precise test of the Standard Model.

The Standard Model predicts that the odds of a positively charged kaon decaying into a positively charged pion and a neutrino–antineutrino pair (K+ → π+ ν ν) are only about one in ten billion, with an uncertainty of less than ten percent. Finding a deviation, even if small, from this prediction would indicate new physics beyond the Standard Model.

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The quantum superposition principle has been tested on a scale as never before in a new study by scientists at the University of Vienna in collaboration with the University of Basel. Hot, complex molecules composed of nearly two thousand atoms were brought into a quantum superposition and made to interfere. By confirming this phenomenon—” the heart of quantum mechanics,” in Richard Feynman’s words—on a new mass scale, improved constraints on alternative theories to quantum mechanics have been placed. The work will be published in Nature Physics.

Quantum to classical?

The superposition principle is a hallmark of quantum theory which emerges from one of the most fundamental equations of quantum mechanics, the Schrödinger equation. It describes particles in the framework of wave functions, which, much like on the surface of a pond, can exhibit . But in contrast to water waves, which are a collective behavior of many interacting , quantum waves can also be associated with isolated single particles.

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