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Category: particle physics – Page 571

Is search of the sound of silence.

To a physicist, perfect quiet is the ultimate noise. Silence your cellphone, still your thoughts, and muffle every kind of vibration, and you would still be left with quantum noise. It represents an indeterminacy deep within nature, bursts of static and inexplicable motions that cannot be gotten rid of, or made sense of. It seems devoid of meaning.

Considering how pervasive this noise is, you might presume that physicists would have a good explanation for it. But it remains one of the great unsolved problems in science. Quantum theory is silent not just on where the noise comes from, but on how exactly it enters the world. The theory’s defining equation, the Schrödinger equation, is completely deterministic. There is no noise in it at all. To explain why we observe quantum particles to be noisy, we need some additional principle.

For physicists in the Niels Bohr tradition, the act of observation itself is decisive. The Schrödinger equation defines a menu of possibilities for what a particle could do, but only when measured does the particle actually do anything, choosing at random from the menu. Identical particles will make different choices, causing the outcomes of fundamental processes to vary in an uncontrollable way. On Bohr’s view, quantum noise cannot be explained further. It is what physicist John Wheeler called “an elementary act of creation,” with no antecedents. Genesis was not a singular event in the distant past, but an ongoing process that we bring about. We create the world by observing it.

Continue reading “The Noise at the Bottom of the Universe” | >

The universal quantum gate to enable long distance communications with QC without degradation.

Scientists have now developed a universal quantum gate, which could become the key component in a quantum computer.

Light particles completely ignore each other. In order that these particles can nevertheless switch each other when processing quantum information, researchers at the Max Planck Institute of Quantum Optics in Garching have now developed a universal quantum gate. Quantum gates are essential elements of a quantum computer. Switching them with photons, i.e. light particles, would have practical advantages over operating them with other carriers of quantum information.

The light-saber fights of the Jedi and Sith in the Star Wars saga may well suggest something different, but light beams do not notice each other. No matter how high their intensity, they cut through each other without hindrance. When individual light particles meet, as is necessary for some applications of quantum information technology, nothing at all happens. Photons can therefore not switch each other just like that, as would have to be the case if one wanted to use them to operate a quantum gate, the elementary computing unit of a quantum computer.

Continue reading “Researchers Develop A Universal Quantum Gate” | >

Physicists from New Zealand’s University of Otago have used steerable ‘optical tweezers’ to split minute clouds of ultracold atoms and slowly smash them together to directly observe a key theoretical principle of quantum mechanics.

The principle, known as Pauli Exclusion, places fundamental constraints on the behavior of groups of identical particles and underpins the structure and stability of atoms as well as the mechanical, electrical, magnetic and chemical properties of almost all materials.

Otago Physics researcher Associate Professor Niels Kjærgaard led the research, which is newly published in the prestigious journal Nature Communications (“Multiple scattering dynamics of fermions at an isolated p-wave resonance”).

Observing the Pauli Exclusion Principle by Slowly Colliding Atomic Clouds

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Our best theory of reality says things only become real when we look at them. Understanding how the universe came to be requires a better explanation.

By Jon Cartwright

WHERE, when you aren’t looking at it, is a subatomic particle? A quantum physicist would probably answer: sort of all over the place. An unobserved particle is a wisp of reality, a shimmer of existence – there isn’t a good metaphor for it, because it is vague both by definition and by nature. Until you do have a peek. Then it becomes a particle proper, it can be put into words, it is a thing with a place.

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By laser-cooling atom clusters and studying their movements, a Missouri University of Science and Technology researcher hopes to better understand how atoms and their components are impacted and directed by environmental factors.

With a $400,000 grant from the National Science Foundation, Dr. Daniel Fischer, assistant professor of physics at Missouri S&T, tests the limits of quantum mechanics through his project titled “Control and Analysis of Atomic Few-Body Dynamics.”

In a hand-built vacuum chamber, Fischer manipulates lithium atoms by trapping them in a magnetic field and then shooting them with different lasers. This gives Fischer a large variety of initial states to test. Tests range from single, polarized atoms to larger groups that are laser-cooled to a consistent energy level. By doing so, Fischer works to help unravel the “few-body problem” that continues to confound the world of physics.

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Great work by my friends at ORNL.

In a review paper published in ACS Nano, Olga Ovchinnikova and colleagues provide an overview of existing paths to 3D materials, but the ultimate goal is to create and customize material at the atomic scale. Material would be assembled atom by atom, much like children can use Legos to build a car or castle brick by brick. This concept, known as directed matter, could lead to virtually perfect materials and products because many limitations of conventional manufacturing techniques would be eliminated.

“Being able to assemble matter atom by atom in 3D will enable us to design materials that are stronger and lighter, more robust in extreme environments and provide economical solutions for energy, chemistry and informatics,” Ovchinnikova said.

Fundamentally, directed matter eliminates the need to remove unwanted material by lithography, etching or other traditional methods. These processes have served society well, researchers noted, but the next generation of materials and products require a new approach.

Continue reading “Additive manufacturing techniques featuring atomic precision could one day create materials with Legos flexibility and Terminator toughness” | >

Graphene, a two-dimensional wonder-material composed of a single layer of carbon atoms linked in a hexagonal chicken-wire pattern, has attracted intense interest for its phenomenal ability to conduct electricity. Now University of Illinois at Chicago researchers have used rod-shaped bacteria — precisely aligned in an electric field, then vacuum-shrunk under a graphene sheet — to introduce nanoscale ripples in the material, causing it to conduct electrons differently in perpendicular directions.

The resulting material, sort of a graphene nano-corduroy, can be applied to a silicon chip and may add to graphene’s almost limitless potential in electronics and nanotechnology. The finding is reported in the journal ACS Nano.

“The current across the graphene wrinkles is less than the current along them,” says Vikas Berry, associate professor and interim head of chemical engineering at UIC, who led the research.

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Stable nanomagnets that ultimately improves data storage on the smallest of devices.

Abstract: So-called “zero-point energy” is a term familiar to some cinema lovers or series fans; in the fictional world of animated films such as “The Incredibles” or the TV series “Stargate Atlantis”, it denotes a powerful and virtually inexhaustible energy source. Whether it could ever be used as such is arguable. Scientists at Jülich have now found out that it plays an important role in the stability of nanomagnets. These are of great technical interest for the magnetic storage of data, but so far have never been sufficiently stable. Researchers are now pointing the way to making it possible to produce nanomagnets with low zero-point energy and thus a higher degree of stability (Nano Letters, DOI: 10.1021/acs.nanolett.6b01344).

Since the 1970s, the number of components in computer chips has doubled every one to two years, their size diminishing. This development has made the production of small, powerful computers such as smart phones possible for the first time. In the meantime, many components are only about as big as a virus and the miniaturization process has slowed down. This is because below approximately a nanometre, a billionth of a meter in size, quantum effects come into play. They make it harder, for example, to stabilise magnetic moments. Researchers worldwide are looking for suitable materials for magnetically stable nanomagnets so that data can be stored safely in the smallest of spaces.

In this context, stable means that the magnetic moments point consistently in one of two preassigned directions. The direction then codes the bit. However, the magnetic moments of atoms are always in motion. The trigger here is the so-called zero-point energy, the energy that a quantum mechanical system possesses in its ground state at absolute zero temperature. “It makes the magnetic moments of atoms fluctuate even at the lowest of temperatures and thus works against the stability of the magnetic moments”, explains Dr. Julen Ibañez-Azpiroz, from the Helmholtz Young Investigators Group “Functional Nanoscale Structure Probe and Simulation Laboratory” at the Peter Grünberg Institute and at the Institute for Advanced Simulation. When too much energy exists within the system, the magnetic moments turn over and the saved information is lost.

Continue reading “Atomic bits despite zero-point energy? Jülich scientists explore novel ways of developing stable nanomagnets” | >