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Category: quantum physics

Thinking on different wavelengths: New approach to circuit design introduces next-level quantum computing

Quantum computing represents a potential breakthrough technology that could far surpass the technical limitations of modern-day computing systems for some tasks. However, putting together practical, large-scale quantum computers remains challenging, particularly because of the complex and delicate techniques involved.

In some quantum computing systems, single ions (charged atoms such as strontium) are trapped and exposed to electromagnetic fields including laser light to produce certain effects, used to perform calculations. Such circuits require many different wavelengths of light to be introduced into different positions of the device, meaning that numerous laser beams have to be properly arranged and delivered to the designated area. In these cases, the practical limitations of delivering many different beams of light around within a limited space become a difficulty.

To address this, researchers from The University of Osaka investigated unique ways to deliver light in a limited space. Their work revealed a power-efficient nanophotonic circuit with optical fibers attached to waveguides to deliver six different laser beams to their destinations. The findings have been published in APL Quantum.

New approach to circuit design introduces next-level quantum computing

Quantum computing represents a potential breakthrough technology that could far surpass the technical limitations of modern-day computing systems for some tasks. However, putting together practical, large-scale quantum computers remains challenging, particularly because of the complex and delicate techniques involved.

An example configuration of the proposed laser delivery photonic circuit chip. (Image: Reproduced from DOI:10.1063/5.0300216, CC BY)

Physicists built a perfect conductor from ultracold atoms

Scientists have built a quantum “wire” where atoms collide endlessly—but energy and motion never slow down. Researchers at TU Wien have discovered a quantum system where energy and mass move with perfect efficiency. In an ultracold gas of atoms confined to a single line, countless collisions occur—but nothing slows down. Instead of diffusing like heat in metal, motion travels cleanly and undiminished, much like a Newton’s cradle. The finding reveals a striking form of transport that breaks the usual rules of resistance.

In everyday physics, transport describes how things move from one place to another. Electric charge flows through wires, heat spreads through metal, and water travels through pipes. In each case, scientists can measure how easily charge, energy, or mass moves through a material. Under normal conditions, that movement is slowed by friction and collisions, creating resistance that weakens or eventually stops the flow.

Researchers at TU Wien have now demonstrated a rare exception. In a carefully designed experiment, they observed a physical system in which transport does not degrade at all.

Collaboration of elementary particles: How teamwork among photon pairs overcomes quantum errors

Some things are easier to achieve if you’re not alone. As researchers from the University of Rostock, Germany have shown, this very human insight also applies to the most fundamental building blocks of nature.

At its very core, quantum mechanics postulates that everything is made out of elementary particles, which cannot be split up into even smaller units. This made Ph.D. candidate Vera Neef, first author of the recent publication “Pairing particles into holonomies,” wonder: “What can two particles only accomplish if they work as a team? Can they jointly achieve something, that is impossible for one particle alone?”

Software allows scientists to simulate nanodevices on a supercomputer

From computers to smartphones, from smart appliances to the internet itself, the technology we use every day only exists thanks to decades of improvements in the semiconductor industry, that have allowed engineers to keep miniaturizing transistors and fitting more and more of them onto integrated circuits, or microchips. It’s the famous Moore’s scaling law, the observation—rather than an actual law—that the number of transistors on an integrated circuit tends to double roughly every two years.

The current growth of artificial intelligence, robotics and cloud computing calls for more powerful chips made with even smaller transistors, which at this point means creating components that are only a few nanometers (or millionths of millimeters) in size. At that scale, classical physics is no longer enough to predict how the device will function, because, among other effects, electrons get so close to each other that quantum interactions between them can hugely affect the performance of the device.

AI makes quantum field theories computable

An old puzzle in particle physics has been solved: How can quantum field theories be best formulated on a lattice to optimally simulate them on a computer? The answer comes from AI.

Quantum field theories are the foundation of modern physics. They tell us how particles behave and how their interactions can be described. However, many complicated questions in particle physics cannot be answered simply with pen and paper, but only through extremely complex quantum field theory computer simulations.

This presents exceptionally complex problems: Quantum field theories can be formulated in different ways on a computer. In principle, all of them yield the same physical predictions—but in radically different ways. Some variants are computationally completely unusable, inaccurate, or inefficient, while others are surprisingly practical. For decades, researchers have been searching for the optimal way to embed quantum theories in computer simulations. Now, a team from TU Wien, together with teams from the U.S. and Switzerland, has shown that artificial intelligence can bring about tremendous progress in this area. Their paper is published in Physical Review Letters.

Establishing a new QM/MM design principle based on electronic-state responses

A research team has proposed a new design principle for QM/MM (quantum mechanics/molecular mechanics) simulations. The approach enables objective and automatic determination of the quantum-mechanical region based on electronic-state changes, addressing a long-standing challenge in multiscale molecular simulations.

The researchers included Professor Hirotoshi Mori (Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University), together with Nichika Ozawa (first-year Ph.D. student at Ochanomizu University) and Assistant Professor Nahoko Kuroki of Ochanomizu University.

The findings are published in the journal Advanced Science as a cover article.

Superconducting nanowire memory array achieves significantly lower error rate

Quantum computers, systems that process information leveraging quantum mechanical effects, will require faster and energy-efficient memory components, which will allow them to perform well on complex tasks. Superconducting memories are promising memory devices that are made from superconductors, materials that conduct electricity with a resistance of zero when cooled below a critical temperature.

These memory devices could be faster and consume significantly less energy than existing memories based on superconductors. Despite their potential, most existing superconducting memories are prone to errors and are difficult to scale up to create larger systems containing several memory cells.

Researchers at Massachusetts Institute of Technology (MIT) recently developed a new scalable superconducting memory that is based on nanowires, one-dimensional (1D) nanostructures with unique optoelectronic properties. This memory, introduced in a paper published in Nature Electronics, was found to be less prone to errors than many other superconducting nanowire-based memories introduced in the past.

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