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Category: computing

Quantum teleportation carries microwave states at temperatures up to 4 K, beating classical limit

A growing number of quantum engineers worldwide have been trying to realize large-scale quantum networks, which consist of several connected quantum computers or devices that share information with each other. The successful realization of these networks could potentially pave the way for the realization of new high-speed and secure communication systems, or even of a quantum version of the internet.

A key challenge when trying to realize large-scale quantum networks is ensuring that the quantum properties of microwave signals can be reliably transferred from one location to another. These signals are highly sensitive to random energy fluctuations associated with heat. Thus, systems introduced so far typically operate inside cooling machines known as dilution refrigerators.

Researchers at Walther-Meißner-Institute (WMI) and Technical University of Munich have introduced a new approach to successfully transfer quantum microwave states between two separate dilution refrigerators connected by a warmer superconducting cable, with temperatures of up to 4K.

Metamaterials enable control of heat transfer at nanoscale, potentially transforming energy and electronics

Heat behaves in predictable ways: a hot cup of coffee cools, a laptop warms your hands, the sun heats Earth. But at scales thousands of times smaller than a human hair, those rules begin to break down, and scientists are learning how to take advantage of that.

A new study, published in Nature from researchers at Carnegie Mellon University, in collaboration with Stanford University and Purdue University, shows that heat can be manipulated far more powerfully than previously demonstrated using carefully engineered metamaterials. The work offers one of the clearest experimental confirmations yet that heat transfer can be actively designed and enhanced.

At the core of the discovery is a phenomenon called near-field radiative heat transfer. When two objects are brought extremely close together—just a few hundred nanometers apart—heat doesn’t simply radiate away in the usual sense. Instead, it can tunnel across the gap through electromagnetic waves, dramatically increasing how much energy flows between them.

Memory-preserving transistors could bypass the Boltzmann limit

Researchers have created a new theoretical framework that shows how memory-preserving “memtransistors” could overcome the intrinsic limits in efficiency faced by conventional semiconductor transistors, imposed by the laws of thermodynamics.

Led by Victor Lopez-Richard at the Federal University of São Carlos, Brazil, in collaboration with the University of Wurzburg, in Germany, and the University of Richmond, U.S., the researchers showed that further improvements to transistor switching efficiency could be reached simply by harnessing memory effects that are already present in many nanoscale devices. The research has been published in Physical Review Applied.

Optical device uses humidity to unlock hidden information and offers new option for data storage

Engineers at the University of California San Diego have developed an optical device that reveals hidden images and changes colors in response to different levels of humidity. The technology, published in Light: Science & Applications, could lead to the development of new anti-counterfeiting labels, secure data storage, interactive displays, and environmental sensors.

The device works by displaying different images depending on moisture levels in the air. Under normal conditions or low humidity levels, one image (UC San Diego Triton logo) is visible. When humidity increases, a second image (UC San Diego library logo) emerges and conceals the first. This transition can be triggered even when a person breathes on the device. It happens in a fraction of a second and can be repeated many times.

“You can imagine using this as a built-in security feature with the environment acting like a key that unlocks different pieces of information,” said study first author Asad Nauman, an electrical and computer engineering postdoctoral researcher at UC San Diego. “One example would be something like a credit card security tag, where you can blow on it and reveal a hidden code. Another application would be an environmental sensor that changes color as the humidity changes.”

Q&A: How researchers are building next-gen quantum computers

Quantum computers have the potential to transform science, accelerating breakthroughs in drug development, cosmology, materials science, nuclear physics, and more.

To make this future a reality, researchers at Lawrence Berkeley National Laboratory (Berkeley Lab) are partnering with industry, academia, and the national labs to drive advances across the quantum computing “stack”—the hardware, software, and controls designed to ensure error-corrected quantum calculations.

“Making a functional quantum computer requires much more than qubits alone. It takes an entire technology stack that can harness quantum science for real-world applications,” said Chris Spitzer, operations lead at the Advanced Quantum Testbed (AQT).

Nvidia is canning the Control Panel, and I can’t be the only one who’s slightly sad to see it go

And two, the Nvidia App can be quite an online-focused affair in a way the old Control Panel was not. Besides the greyed-out checkbox in the Privacy settings labelled “required data” (something Nvidia explains is “Data that is necessary for Nvidia App to operate and cannot be switched off”), it can also lag quite badly on an unstable connection. In my personal experience, anyway.

Still, change comes for us all. I’ll miss the Control Panel’s classic rotating 3D image preview, the charmingly old-school HDCP menu that shows a rendering of an ancient Nvidia GPU plugged into what looks suspiciously like a plasma TV, and of course, the old Global Settings and Program Settings tabs with all of their many intricacies.

But is it progress? Perhaps. You can pry the Windows Control Panel from my cold, dead hands, though. That old clunker simply refuses to die, although I don’t think it’ll be that long before I write a similar obituary.

A More Accurate Prediction of Band-Gap Energies

Temperature is a tuning knob for semiconductor-band-gap energies, which in turn play a key role in the performance of optoelectronic devices. But computational tools for predicting this temperature dependence from first principles struggle to capture the influence of one main factor: many-electron effects in electron–phonon interactions. Xiaoxun Gong at the University of California, Berkeley, and colleagues now demonstrate a computational framework that properly accounts for these effects [1]. Their framework could aid the design of materials and devices with precisely tailored electronic and optical properties.

Theoretical calculations consistently underestimate the strength of electron–phonon interactions and how they modify band gaps at different temperatures. Previous studies indicated that this discrepancy likely stems from insufficient treatment of many-electron effects. To quantify the role of electron–phonon interactions more accurately, Gong and his colleagues have proposed a new framework that breaks down the total temperature-dependent modification of the band gap into various contributions. Within this framework, they analyzed electron–phonon interactions using a many-body perturbation theory, in which electrons’ energies and their perturbation by phonons are captured by the “GW” approximation.

To test their framework, the researchers computed the band gaps of diamond, silicon, and gallium phosphide at different temperatures. They found that the temperature-dependent band-gap modification was enhanced using the GW-based perturbation theory—especially compared to a description based on density-functional theory (DFT), the workhorse tool for first-principles electronic calculations. The new predictions for all three materials showed excellent agreement with previous measurements.

Low-power, flexible radio-frequency transistors break 100 GHz barrier

Over the past decades, electronics engineers worldwide have been trying to develop devices that could enable even faster communications between devices, all while consuming less energy. To meet the demands of the sixth generation (6G) of wireless communication technology, these devices should operate at frequencies above 100 gigahertz (GHz).

So far, developing flexible electronic components that can operate at these high frequencies while consuming little power has proved challenging. One promising approach for fabricating these devices entails the use of carbon nanotubes (CNTs), extremely thin and cylindrical structures with advantageous electrical and thermal properties.

Researchers at Peking University and Stanford University recently developed new flexible and low-power CNT-based transistors that operate at frequencies above 100 GHz. These transistors, presented in a paper published in Nature Electronics, could potentially help to speed up communications between future smartphones, sensors, wearable devices, and other flexible devices.

Imaginary-time technique speeds X-ray scattering simulations by 50-fold for extreme matter

Researchers at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) have developed a new procedure, enabling them to speed up elaborate computer simulations that analyze matter under extreme conditions. In particular, this work improves the evaluation of experiments at large-scale research facilities like the European XFEL—and should facilitate substantial progress, among others, in fusion research and laboratory astrophysics.

The team presented the results in the journal npj Computational Materials.

Sometimes, matter is present in extreme states—such as in stars or in the interior of gas giants where enormous pressures and temperatures prevail. Such conditions can also be produced in the lab, in laser fusion experiments, for instance. In order to understand precisely what happens, researchers use X-ray scattering—as at the European XFEL near Hamburg.

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