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Category: particle physics – Page 305

Scientists from The University of Manchester have developed a novel yet simple method for producing vertical stacks of alternating superconductor and insulator layers of tantalum disulphide (TaS 2). The findings, from a team led by Professor Rahul Nair, could speed up the process of manufacturing such devices – so-called van der Waals heterostructures – with application in high-mobility transistors, photovoltaics and optoelectronics.

Van der Waals heterostructures are much sought after since they display many unique and useful properties not found in naturally occurring materials. In most cases, they are prepared by manually stacking one layer over the other in a time-consuming and labour-intensive process.

Electron microscopy image of the synthesized 6R TaS 2 with an atomic model of the material on the left. The brown spheres represent Ta atoms and the yellow spheres represent sulphur atoms. The atomic positions and arrangement in the microscopic image are an exact match with the model, confirming its structure. (Image: University of Manchester)

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A special bonding state between atoms has been created in the laboratory for the first time: With a laser beam, atoms can be polarized so that they are positively charged on one side and negatively charged on the other. This makes them attract each other creating a very special bonding state—much weaker than the bond between two atoms in an ordinary molecule, but still measurable. The attraction comes from the polarized atoms themselves, but it is the laser beam that gives them the ability to do so—in a sense, it is a “molecule” of light and matter.

Theoretically, this effect has been predicted for a long time, but now scientists at the Vienna Center for Quantum Science and Technology (VCQ) at TU Wien, in cooperation with the University of Innsbruck, have succeeded in measuring this exotic atomic bond for the first time. This interaction is useful for manipulating extremely cold atoms, and the effect could also play a role in the formation of molecules in space. The results have now been published in the scientific journal Physical Review X.

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Atoms are notoriously difficult to control. They zigzag like fireflies, tunnel out of the strongest containers and jitter even at temperatures near absolute zero.

Nonetheless, scientists need to trap and manipulate in order for , such as atomic clocks or quantum computers, to operate properly. If individual atoms can be corralled and controlled in large arrays, they can serve as quantum bits, or qubits—tiny discrete units of information whose state or orientation may eventually be used to carry out calculations at speeds far greater than the fastest supercomputer.

Researchers at the National Institute of Standards and Technology (NIST), together with collaborators from JILA—a joint institute of the University of Colorado and NIST in Boulder—have for the first time demonstrated that they can trap single atoms using a novel miniaturized version of “”—a system that grabs atoms using a laser beam as chopsticks.

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Peer long enough into the heavens, and the Universe starts to resemble a city at night. Galaxies take on characteristics of streetlamps cluttering up neighborhoods of dark matter, linked by highways of gas that run along the shores of intergalactic nothingness.

This map of the Universe was preordained, laid out in the tiniest of shivers of quantum physics moments after the Big Bang launched into an expansion of space and time some 13.8 billion years ago.

Yet exactly what those fluctuations were, and how they set in motion the physics that would see atoms pool into the massive cosmic structures we see today is still far from clear.

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Nowadays, the development of renewable energy sources, such as wind, solar, and nuclear energy sources, has become imperative, due to the limited resource constraints of the traditional fossil fuels [1 ]. However, these renewable sources could not deliver a regular power supply as the sources are variable in time and diffuse in space. Thus, the focus has been shifted to the electrical energy storage to smooth the intermittency of the energy sources. Rechargeable battery has the ability to store chemical energy and convert it into electrical energy with high efficiency [ 2]. Lithium-ion battery (LIB), as one typical rechargeable electrochemical battery, has dominated the markets of portable electronic devices, electric vehicles, and hybrid electric vehicles in the past decades, due to its high output voltages, high energy densities, and long cycle life; even though the high cost and the shortage of lithium resources are inhibiting the application of LIB in large-scale energy storage [[3], [4], [5], [6], [7], [8], [9]].

Sodium-ion battery (SIB) is one promising alternative to LIB, with comparable performance to that of LIB, abundant sodium resources and low price of starting materials [[10], [11], [12], [13]]. As Na atom is heavier and larger than those of Li atom, the gravimetric and volumetric energy density of Na-ion battery are expected to not exceed those of the Li analogues [14]. However, energy density would not be considered as the critical issue in the field of large-scale grid support, for which the operating cost and the battery durability are the most important aspects [15,16].

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Quantum entanglement is one of the most fundamental and intriguing phenomena in nature. Recent research on entanglement has proven to be a valuable resource for quantum communication and information processing. Now, scientists from Japan have discovered a stable quantum entangled state of two protons on a silicon surface, opening doors to an organic union of classical and quantum computing platforms and potentially strengthening the future of quantum technology.

One of the most interesting phenomena in quantum mechanics is “quantum entanglement.” This phenomenon describes how certain particles are inextricably linked, such that their states can only be described with reference to each other. This particle interaction also forms the basis of quantum computing. And this is why, in recent years, physicists have looked for techniques to generate entanglement. However, these techniques confront a number of engineering hurdles, including limitations in creating large number of “qubits” (quantum bits, the basic unit of quantum information), the need to maintain extremely low temperatures (1 K), and the use of ultrapure materials. Surfaces or interfaces are crucial in the formation of quantum entanglement. Unfortunately, electrons confined to surfaces are prone to “decoherence,” a condition in which there is no defined phase relationship between the two distinct states.

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Entanglement is an ubiquitous concept in modern physics research: it occurs in subjects ranging from quantum gravity to quantum computing. In a publication that appeared in Physical Review Letters last week, UvA-IoP physicist Michael Walter and his collaborator Sepehr Nezami shed new light on the properties of quantum entanglement—in particular, for cases in which many particles are involved.

In the quantum world, physical phenomena occur that we never observe in our large scale everyday world. One of these phenomena is quantum entanglement, where two or more quantum systems share certain properties in a way that affects measurements on the systems. The famous example is that of two electrons that can be entangled in such a way that—even when taken very far apart—they can be observed to spin in the same direction, say clockwise or counterclockwise, despite the fact that the spinning direction of neither of the individual electrons can be predicted beforehand.

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