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Category: particle physics

A method for locating seams of gold and other heavy metals is the unlikely spin-off of Swinburne’s involvement in a huge experiment to detect dark matter down a mine in Stawell, Victoria.

Associate Professor Alan Duffy, from Swinburne’s Centre for Astrophysics and Supercomputing and a member of the Sodium iodide with Active Background REjection (SABRE) project, said was effectively creating an X-ray of the Earth between the and the surface.

In the mine, the SABRE experiment seeks to detect particles of dark matter, something no one has conclusively achieved yet. Any signal from dark matter would be miniscule, and so the SABRE team created a phenomenally sensitive detector, which, it turns out, is also sensitive to a host of cosmic particles that can help us to locate gold.

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Two independent research teams recently published studies indicating they’ve successfully teleported a qutrit — possibly within days of each other. Now, both await the scientific process of peer review to see which will ultimately get credit for being the first humans to do so.

But what’s a qutrit? It’s a lot like a qubit, an entangled pair of particles used to carry information in a quantum computing system. Qubits are analogous to bits, the binary units of information used by classical computers like the one you’re reading this on. Where bits can be represented by the numbers zero and one, qubits can be zero, one, or both at the same time. Trits, used in classical ternary systems, add a two into the mix. And qutrits are the quantum version of trits, capable of carrying more information than their qubit counterparts.

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Researchers at the Massachusetts Institute of Technology (MIT) have recently developed a metric that can be used to capture the space of collider events based on the earth mover’s distance (EMD), a measure used to evaluate dissimilarity between two multi-dimensional probability distributions. The metric they proposed, outlined in a paper published in Physical Review Letters, could enable the development of new powerful tools to analyze and visualize collider data, which do not rely on a choice of observables.

“Our research is motivated by a remarkably simple question: When are two similar?” Eric Metodiev, one of the researchers who carried out the study, told Phys.org. “At the Large Hadron Collider (LHC), protons are smashed together at extremely high energies and each collision produces a complex mosaic of particles. Two collider events can look similar, even if they consist of different numbers and types of particles. This is analogous to how two mosaics can look similar, even if they are made up of different numbers and colors of tiles.”

In their study, Metodiev and his colleagues set out to capture the similarity between collider events in a way that is conceptually useful for particle physics. To do this, they employed a strategy that merges ideas related to optimal transport theory, which is often used to develop cutting-edge image recognition tools, with insights from , a construct that describes fundamental particle interactions.

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Many phenomena of the natural world evidence symmetries in their dynamic evolution which help researchers to better understand a system’s inner mechanism. In quantum physics, however, these symmetries are not always achieved. In laboratory experiments with ultracold lithium atoms, researchers from the Center for Quantum Dynamics at Heidelberg University have proven for the first time the theoretically predicted deviation from classical symmetry. Their results were published in the journal Science.

“In the world of classical , the energy of an ideal gas rises proportionally with the pressure applied. This is a direct consequence of scale symmetry, and the same relation is true in every scale invariant system. In the world of quantum mechanics, however, the interactions between the quantum particles can become so strong that this classical scale symmetry no longer applies,” explains Associate Professor Dr. Tilman Enss from the Institute for Theoretical Physics. His research group collaborated with Professor Dr. Selim Jochim’s group at the Institute for Physics.

In their experiments, the researchers studied the behaviour of an ultracold, superfluid gas of lithium atoms. When the gas is moved out of its equilibrium state, it starts to repeatedly expand and contract in a “breathing” motion. Unlike classical particles, these can bind into pairs and, as a result, the superfluid becomes stiffer the more it is compressed. The group headed by primary authors Dr. Puneet Murthy and Dr. Nicolo Defenu—colleagues of Prof. Jochim and Dr. Enss—observed this deviation from classical scale symmetry and thereby directly verified the quantum nature of this system. The researchers report that this effect gives a better insight into the behaviour of systems with similar properties such as graphene or superconductors, which have no electrical resistance when they are cooled below a certain critical temperature.

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Dark matter might well be the biggest mystery in the Universe. We know there’s something out there making things move faster than they should. But we don’t know what it is, and we sure as heck don’t know where it came from.

According to a new paper, the origins of dark matter may be more peculiar than we know. Perhaps, they were particles that appeared in a very brief period of time, just fractions of fractions of a second, before the Big Bang.

This doesn’t just suggest a new connection between particle physics and astronomy; if this hypothesis holds, it could indicate a new way to search for the mysterious stuff.

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GOLD that’s just two atoms thick has been created in a lab by British scientists.

The “world’s thinnest gold” is one million times thinner than a fingernail – and is so thin, it’s technically regarded as “two dimensional”.

The official measurement is 0.47 nanometres, made possible because the gold is made up of just two atoms sitting on top of each other.

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Researchers in the Department of Physics of ETH Zurich have measured how electrons in so-called transition metals get redistributed within a fraction of an optical oscillation cycle. They observed the electrons getting concentrated around the metal atoms within less than a femtosecond. This regrouping might influence important macroscopic properties of these compounds, such as electrical conductivity, magnetization or optical characteristics. The work therefore suggests a route to controlling these properties on extremely fast time scales.

The distribution of electrons in , which represent a large part of the periodic table of chemical elements, is responsible for many of their interesting properties used in applications. The magnetic properties of some of the members of this group of materials are, for example, exploited for data storage, whereas others exhibit excellent electrical conductivity. Transition metals also have a decisive role for novel materials with more exotic behaviour that results from strong interactions between the electrons. Such materials are promising candidates for a wide range of future applications.

In their experiment, whose results they report in a paper published today in Nature Physics, Mikhail Volkov and colleagues in the Ultrafast Laser Physics group of Prof. Ursula Keller exposed thin foils of the transition metals titanium and zirconium to short laser pulses. They observed the redistribution of the electrons by recording the resulting changes in optical properties of the metals in the extreme ultraviolet (XUV) domain. In order to be able to follow the induced changes with sufficient temporal resolution, XUV pulses with a duration of only few hundred attoseconds (10-18 s) were employed in the measurement. By comparing the experimental results with theoretical models, developed by the group of Prof. Angel Rubio at the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg, the researchers established that the change unfolding in less than a femtosecond (10-15 s) is due to a modification of the electron localization in the vicinity of the metal atoms.

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When you pop a tray of water into the freezer, you get ice cubes. Now, researchers from the University of Colorado Boulder and the University of Toronto have achieved a similar transition using clouds of ultracold atoms.

In a study that will appear August 2 in the journal Science Advances, the team discovered that it could nudge these to undergo transitions between “dynamical phases”—essentially, jumping between two states in which the behave in completely different ways.

“This happens abruptly, and it resembles the we see in systems like water becoming ice,” said study co-author Ana Maria Rey. “But unlike that tray of ice cubes in the freezer, these phases don’t exist in equilibrium. Instead, atoms are constantly shifting and evolving over time.”

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The phenomenon known as “tunneling” is one of the best-known predictions of quantum physics, because it so dramatically confounds our classical intuition for how objects ought to behave. If you create a narrow region of space that a particle would have to have a relatively high energy to enter, classical reasoning tells us that low-energy particles heading toward that region should reflect off the boundary with 100% probability. Instead, there is a tiny chance of finding those particles on the far side of the region, with no loss of energy. It’s as if they simply evaded the “barrier” region by making a “tunnel” through it.

It’s very important to note that this phenomenon is absolutely and unquestionably real, demonstrated in countless ways. The most dramatic of these is sunlight— the Sun wouldn’t be able to fuse hydrogen into helium without quantum tunneling— but it’s also got more down-to-earth technological applications. Tunneling serves as the basis for Scanning Tunneling Microscopy, which uses the tunneling of electrons across a tiny gap between a sharp tip and a surface to produce maps of that surface that can readily resolve single atoms. It’s also essential for the Josephson effect, which is the basis of superconducting detectors of magnetic fields and some of the superconducting systems proposed for quantum computing.

So, there is absolutely no debate among physicists about whether quantum tunneling is a thing that happens. Physicists get a bit twitchy without something to argue over, though, and you don’t have to dig into tunneling (heh) very far to find a disputed question, namely “How long does quantum tunneling take?”

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