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Category: quantum physics – Page 491

Quark Picture Put to the Test

A measurement of the charge radius of an aluminum nucleus probes the assumption that there are only three families of quarks.

In the standard model of particle physics, matter is made of elementary particles called quarks and leptons. Quarks are the heavy constituents that form, for example, protons and neutrons, whereas leptons are the light constituents, such as the electron. The six known quarks—up, down, charm, strange, top, and bottom—are split into three families. But could there be a fourth family? Answering that question would require hundreds of different measurements in particle and nuclear physics. However, not all these measurements are yet available or precise enough, and many parameter values are only inferred or extrapolated. Now Peter Plattner at CERN in Switzerland and his colleagues show how a single one of these measurements can shift our understanding of this fundamental question [1].

In the quantum-mechanical framework of the standard model, quarks can oscillate among their different flavors. The best-known example occurs in the beta decay of radioactive nuclei: a proton is transformed into a neutron (or vice versa) when one of its quarks oscillates from up to down (or down to up). The rate of beta decay depends on many factors involving both nuclear and atomic physics, but the rate at which the quarks oscillate is described by a single quantity: Vud, the so-called matrix element of the transformation of an up quark into a down quark.

How AI and quantum physics link up to consciousness

Will artificial intelligence serve humanity — or will it spawn a new species of conscious digital beings with their own agenda?

It’s a question that has sparked scores of science-fiction plots, from “Colossus: The Forbin Project” in 1970, to “The Matrix” in 1999, to this year’s big-budget tale about AI vs. humans, “The Creator.”

The same question has also been lurking behind the OpenAI leadership struggle — in which CEO Sam Altman won out over the nonprofit board members who fired him a week earlier.

The Universe in a lab: Testing alternate cosmology using a cloud of atoms

In the basement of Kirchhoff-Institut für Physik in Germany, researchers have been simulating the Universe as it might have existed shortly after the Big Bang. They have created a tabletop quantum field simulation that involves using magnets and lasers to control a sample of potassium-39 atoms that is held close to absolute zero. They then use equations to translate the results at this small scale to explore possible features of the early Universe.

The work done so far shows that it’s possible to simulate a Universe with a different curvature. In a positively curved universe, if you travel in any direction in a straight line, you will come back to where you started. In a negatively curved universe, space is bent in a saddle shape. The Universe is currently flat or nearly flat, according to Marius Sparn, a PhD student at Kirchhoff-Institut für Physik. But at the beginning of its existence, it might have been more positively or negatively curved.

Diamond-stretching technique makes qubits more stable and controllable

Researchers are claiming a breakthrough in quantum communications, thanks to a new diamond-stretching technique they say greatly increases the temperatures at which qubits remain entangled, while also making them microwave-controllable.

Quantum networking is an emerging field that uses weird quantum phenomena to send and receive information. These networks will be impossible to hack, and will use quantum entanglement to cover large distances, creating pairs of qubits which mirror each other’s quantum state without any physical connection.

Diamond-based qubits are capable of maintaining their state of entanglement for a decent length of time – but only provided they’re kept incredibly cold – just a hair above absolute zero. That limits their usefulness, because it’d mean you’d need a giant, energy-intensive cooling apparatus at every node of your quantum network.

Researchers invent new way to stretch diamond for better quantum bits

A future quantum network may become less of a stretch thanks to researchers at the University of Chicago, Argonne National Laboratory and Cambridge University.

A team of researchers announced a breakthrough in quantum network engineering. By “stretching” thin films of diamond, they created that can operate with significantly reduced equipment and expense. The change also makes the bits easier to control.

The researchers hope the findings, published Nov. 29 in Physical Review X, can make future quantum networks more feasible.

Quantum Squeeze: MIT Unlocks New Dimensions in Precise Clocks

More stable clocks could measure quantum phenomena, including the presence of dark matter.

The practice of keeping time relies on stable oscillations. In grandfather clocks, the length of a second is marked by a single swing of the pendulum. In digital watches, the vibrations of a quartz crystal mark much smaller fractions of time. And in atomic clocks, the world’s state-of-the-art timekeepers, the oscillations of a laser beam stimulate atoms to vibrate at 9.2 billion times per second. These smallest, most stable divisions of time set the timing for today’s satellite communications, GPS systems, and financial markets.

A clock’s stability depends on the noise in its environment. A slight wind can throw a pendulum’s swing out of sync. And heat can disrupt the oscillations of atoms in an atomic clock. Eliminating such environmental effects can improve a clock’s precision. But only by so much.

Breakthrough in Quantum Storage of Entangled Photons May Usher Age of Solid State-based Quantum Networks

Chinese researchers report the successful quantum storage of entangled photons at telecom wavelengths within a crystal, in a breakthrough achievement that reportedly lasted 387 times longer than past similar experiments.

The research team, based at Nanjing University, says their findings could potentially “pave the way for realizing quantum networks based on solid-state devices.”

The Coming Quantum Internet

Alibaba Shuts Down its Quantum Computing Effort

In case you missed it, China’s e-commerce giant Alibaba has shut down its quantum computing research effort. It’s not entirely clear what drove the change. Reuters’ reported earlier this week that Alibaba “cut a quantum computing laboratory and team from its research arm, donating both the lab and related experimental equipment to Zhejiang University.”

Alibaba was a relatively early entrant among giant e-commerce/cloud providers into quantum computing research, placing the effort in its Alibaba’s DAMO Academy research organization. There are reports it had invested on the order of $15 billion in the effort. According to the Reuters report, about 30 employees are being released with and effort under way to find positions for them at Zhejiang.

Rather than being tied to specific issues with the quantum research, the prevailing opinion seems to be that the quantum work was caught in the larger turmoil surrounding Alibaba and its ongoing reorganization. The company said its DAMO organization will deepen its work on AI and machining learning research which may be able to have a nearer-term impact on Alibaba’s business.

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