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Category: quantum physics – Page 4

Scientists build a quantum computer that can repair itself using recycled atoms

Like their conventional counterparts, quantum computers can also break down. They can sometimes lose the atoms they manipulate to function, which can stop calculations dead in their tracks. But scientists at the US-based firm Atom Computing have demonstrated a solution that allows a quantum computer to repair itself while it’s still running.

The team zeroed in on quantum computers that use neutral atoms (atoms with equal numbers of protons and electrons). These individual atoms are the qubits, or the basic building blocks of a quantum computer’s memory. They are held in place by laser beams called optical tweezers, but the setup is not foolproof.

Occasionally, an atom slips out of its trap and disappears. When this happens mid-calculation, the whole process can grind to a halt because the computer can’t function with a missing part.

Flat Fermi surface in altermagnets enables quantum limit spin currents

The key feature of spintronic devices is their ability to use spin currents to transfer momentum, enabling low-energy, high-speed storage and logical signal control. These devices are usually manipulated by electric currents and fields. The charge-to-spin conversion efficiency (CSE) is a key metric for evaluating their performance.

Now, scientists from the Institute of Metal Research (IMR) of the Chinese Academy of Sciences have proposed a new deep correlation between the spin splitting torque (SST) and the Fermi surface geometry, achieving a quantum limit of 100% in a system with a flat Fermi surface. These results were published in Physical Review Letters on December 16.

Physicists Propose First-Ever Experiment To Manipulate Gravitational Waves

When massive cosmic objects such as black holes merge or neutron stars crash into one another, they can produce gravitational waves. These ripples move through the universe at the speed of light and create extremely small changes in the structure of space-time. Their existence was first predicted by Albert Einstein, and scientists confirmed them experimentally for the first time in 2015.

Building on this discovery, Prof. Ralf Schützhold, a theoretical physicist at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), is proposing a bold new step.

Schützhold has developed a concept for an experiment that would go beyond detecting gravitational waves and instead allow researchers to influence them. The proposal, published in the journal Physical Review Letters, could also help clarify whether gravity follows quantum rules, a question that remains unresolved in modern physics.

Physicists push superconducting diodes to high temperatures

For the first time, researchers in China have demonstrated a high-temperature superconducting diode effect, which allows a supercurrent to flow in both directions. Published in Nature Physics, the team’s result could help address the noisy signals that pose a fundamental challenge in quantum computing.

A diode is a device that shows an asymmetric electrical response, allowing current to flow more easily in one direction than the other. Until recently, diode behavior had only been observed in conventional, non-superconducting electrical systems—but in 2020, a team of researchers in Japan became the first to demonstrate the diode effect in a superconductor. Ever since, this effect has gained increasing attention for its potential in practical quantum computing.

“However, most of the reported superconducting diodes work at low temperatures around 10 Kelvin, and often require an external magnetic field,” explains Ding Zhang at Tsinghua University and the Beijing Academy of Quantum Information Sciences, who led the research. “The diode efficiency is also low for many superconducting diodes.”

Shortest light pulse ever created captures ultrafast electron dynamics

Electrons determine everything: how chemical reactions unfold, how materials conduct electricity, how biological molecules transfer energy, and how quantum technologies operate. But electron dynamics happens on attosecond timescales—far too fast for conventional measurement tools.

Researchers have now generated a 19.2-attosecond soft X-ray pulse, which effectively creates a camera capable of capturing these elusive dynamics in real time with unprecedented detail, enabling the observation of processes never observed before. Dr. Fernando Ardana-Lamas, Dr. Seth L. Cousin, Juliette Lignieres, and ICREA Prof. Jens Biegert, at ICFO, has published this new record in Ultrafast Science. At just 19.2 attoseconds long, it is the shortest and brightest soft X-ray pulse ever produced, giving rise to the fastest “camera” in existence.

Flashes of light in the soft X-ray spectral range provide fingerprinting identification, allowing scientists to track how electrons reorganize around specific atoms during reactions or phase transitions. Generating an isolated pulse this short, required innovations in high-harmonic generation, advanced laser engineering, and attosecond metrology. Together, these developments allow researchers to observe electron dynamics, which define material properties, at their natural timescales.

Conventional entanglement can have thousands of hidden topologies in high dimensions

Researchers from the University of the Witwatersrand in South Africa, in collaboration with Huzhou University, discovered that the entanglement workhorse of most quantum optics laboratories can have hidden topologies, reporting the highest ever observed in any system: 48 dimensions with over 17,000 topological signatures, an enormous alphabet for encoding robust quantum information.

Most quantum optics laboratories produce entangled photons by a process of spontaneous parametric downconversion (SPDC), which naturally produces entanglement in “space,” the spatial degrees of freedom of light. Now the team have found that hidden in this space is a world of high-dimensional topologies, offering new paradigms for encoding information and making quantum information immune to noise. The topology was shown using the orbital angular momentum (OAM) of light, from two dimensional to very high dimensions.

Reporting in Nature Communications, the team showed that if one measures the OAM of two entangled photons it can be shown to have a topology: an underlying feature of the entanglement itself. Since OAM can take on an infinite number of possibilities, so too can the topology.

Everything in the universe is a quantum wave

A radical new interpretation of quantum mechanics is offered here. Professor of Quantum Information Science at the University of Oxford, Vlatko Vedral, argues that everything in the universe is a quantum wave. The difficulty of uniting the classical world and the quantum world is overcome; everything is quantum, and the quantum gives rise to the classical. His theory also overcomes the measurement problem, the observer problem, and the problem of quantum entanglement (spooky action at a distance). Poof goes the classical world!

There are, I believe, two main reasons why physics seems stuck at present. The last revolution was quantum mechanics and it began with Heisenberg’s famous paper exactly 100 years ago. And since then, not a single experiment has challenged the quantum description of reality. Not one. The first reason for this century-long absence of a new fundamental theory is that we simply haven’t had the appropriate experimental technology to probe regions where something could go wrong. This has now changed rapidly with the ongoing worldwide race to build a universal quantum computer. The technologies that go into this enterprise and that are being pursued by all the major industrial players are becoming sophisticated enough to test fundamental physics in a non-trivial way. However, there is a second reason for being stuck. It is the fact that we still haven’t agreed on the way to understand quantum mechanics. It is for this reason that I’d like to offer my own interpretation.

Laser light and the quantum nature of gravity: Proposed experiment could measure graviton energy exchange

When two black holes merge or two neutron stars collide, gravitational waves can be generated. They spread at the speed of light and cause tiny distortions in space-time. Albert Einstein predicted their existence, and the first direct experimental observation dates from 2015.

Now, Prof. Ralf Schützhold, theoretical physicist at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), is going one step further. He has conceived an experiment through which gravitational waves can not only be observed but even manipulated. Published in the journal Physical Review Letters, the idea could also deliver new insights into the hitherto only conjectured quantum nature of gravity.

“Gravity affects everything, including light,” says Schützhold. And this interaction also occurs when gravitational waves and light waves meet.

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