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Category: quantum physics – Page 269

Attempts to turn string theory into a workable theory of nature have led to the potential conclusion that our universe is a hologram—that what we perceive as three spatial dimensions is actually composed of only two. The greatest realization of this hologram-led program is a proposal that goes by the awkward and clunky name of the AdS/CFT correspondence, first proposed by string theorist Juan Maldacena in the late 1990s.

The AdS/CFT correspondence is not a solution to the problems posed by per se, but a statement motivated by advances in the theory when one takes the holographic principle seriously. It is also not a by itself, but it does tell us that we are not entirely misguided when we make the bold claim that we live in a , and begin to dream about what that revelation might entail.

We need to, briefly I assure you, unpack these acronyms to see how powerful this connection is, and what it might teach us about the wider . The “AdS” stands for anti-de Sitter, which is a particular kind of solution to Einstein’s general theory of relativity. The name comes from Dutch physicist Willem de Sitter, who constructed a mock universe that was empty of all matter and energy with the exception of a strong outwards curvature.

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String theory found its origins in an attempt to understand the nascent experiments revealing the strong nuclear force. Eventually another theory, one based on particles called quarks and force carriers called gluons, would supplant it, but in the deep mathematical bones of the young string theory physicists would find curious structures, half-glimpsed ghosts, that would point to something more. Something deeper.

String claims that what we call —the point-like entities that wander freely, interact, and bind together to make up the bulk of material existence—are nothing but. Instead, there is but a single kind of fundamental object: the string. These strings, each one existing at the smallest possible limit of existence itself, vibrate. And the way those strings vibrate dictates how they manifest themselves in the larger universe. Like notes on a strummed guitar, a string vibrating with one mode will appear to us as an electron, while another vibrating at a different frequency will appear as a photon, and so on.

String theory is an audacious attempt at a theory of everything. A single mathematical framework that explains the particles that make us who and what we are along with the forces that act as the fundamental messengers among those particles. They are all, every quark in the cosmos and every photon in the field, bits of vibrating strings.

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Even though the guts of General Relativity are obtusely mathematical, and for decades was relegated to math departments rather than proper physics, you get to experience the technological gift of relativity every time you navigate to your favorite restaurant. GPS, the global positioning system, consists of a network of orbiting satellites constantly beaming out precise timing data. Your phone compares those signals to figure out where you are on the Earth. But there is a difference in spacetime between the surface of the Earth and the orbit of the satellites. Without taking general relativity into account, your navigation would simply be incorrect, and you’d be late for dinner.

As revolutions go, general relativity is a big one. And as unifications go, it’s a warning. To make this union happen Einstein had to radically, permanently alter not just our conceptions of gravity as a force acting through space and time, but our conceptions of space and time itself. It took no less than a complete overhaul of our entire philosophical understanding of the relation between space and time to bridge the gap.

And as Einstein would find in the ensuing decades, all the way to the time of his death, that bringing other forces like electromagnetism into the same unified fold would be all but impossible. Electromagnetism, and the other forces, cannot be conceptualized in the same way. Instead we have to use quantum probabilities to make predictions, and when we apply the same technique to gravity we just get infinities.

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Quantum technology is now at a point where practical work can begin on creating the quantum internet. However, numerous challenges must be overcome before this vision becomes a reality. A global-scale quantum internet requires the development of the quantum repeater, a device that stores and manipulates qubits while interacting with or emitting entangled photons. This review examines different approaches to quantum repeaters and networks, covering their conceptual frameworks, architectures, and current progress in experimental implementation.

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Joe McEntee visits the Lawrence Berkeley National Laboratory to learn about QUANT-NET’s plan to create a quantum network tested for distributed quantum computing applications in the US. Joe McEntee visits Lawrence Berkeley National Laboratory (Berkeley Lab) in California to check out progress on the enabling quantum technologies.

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Over the past decade or so, physicists and engineers have been trying to identify new materials that could enable the development of electronic devices that are faster, smaller and more robust. This has become increasingly crucial, as existing technologies are made of materials that are gradually approaching their physical limits.

Antiferromagnetic (AFM) spintronics are devices or components for electronics that couple a flowing current of charge to the ordered spin ‘texture’ of specific materials. In physics, the term spin refers to the intrinsic angular momentum observed in electrons and other particles.

The successful development of AFM spintronics could have very important implications, as it could lead to the creation of devices or components that surpass Moore’s law, a principle first introduced by microchip manufacturer Gordon Earle Moore’s law essentially states that the memory, speed and performance of computers may be expected to double every two years due to the increase in the number of transistors that a microchip can contain.

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A group of researchers in Japan have found yet another interesting way to use AI technology. In a recent research project led by a team from the National Institutes for Quantum Science and Technology (QST) and Osaka University, they were able to translate human brain activity to depict mental images of objects, animals, and landscapes. They released pictures from the research, and the results are pretty astounding.

One of the images that the AI technology was able to decode from the brain activity was a vivid depiction of a leopard with detailed features like spots, ears, and more. Another image depicted an airplane. While we have previously had technology that is able to recreate images from brain activity, this is one of the very few studies that were able to make these mental images visible.

Of these previous studies, the images that could be decoded were fairly limited into several categories, like human faces, letters, and numbers. This new AI brain-decoding technology seems to be able to decode a much broader spectrum of images from the human mind. As the researchers in the study point out, “visualizing mental imagery for arbitrary natural images stands as a significant milestone.”

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