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Category: quantum physics – Page 44

Quantum transport through a constriction in nanosheet gate-all-around transistors

In nanoscale transistors, quantum mechanical effects such as tunneling and quantization significantly influence device characteristics. However, large-scale quantum transport simulation remains a challenging field, making it difficult to account for quantum mechanical effects arising from the complex device geometries. Here, based on large-scale quantum transport simulations, we demonstrate that quantum geometrical effects in stacked nanosheet GAAFETs significantly impact carrier injection characteristics. Discontinuities in confinement energy at the constriction—the junction between the bulk source/drain and nanosheet channel—cause substantial carrier backscattering. This degradation becomes more severe as electrons experience higher effective energy barriers, and is further exacerbated at lower scattering rate, lower doping concentrations, and near Schottky barriers where electron depletion regions form. Considering these quantum mechanical bottlenecks, proper device optimization for future technology nodes requires a full quantum-based device structure design at the large-scale level, which enables unique optimization strategies beyond conventional classical prediction.

Kyoung Yeon Kim and colleagues report the importance of quantum geometrical effects that serve as a bottleneck in stacked nanosheet GAAFETs. This highlights that full quantum mechanics-based device design is crucial for realizing ideal carrier injection characteristics in future technology nodes.

New 3D topological phase of matter exhibits anomalous symmetry at non-zero temperatures

Some phases of matter cannot be described using the conventional framework of symmetry breaking and exhibit a so-called quantum order. One type of quantum order, known as topological order, is characterized by long-range entanglement between particles across an entire system, a ground state degeneracy that depends on the global shape of the system, and a robustness against local disturbances.

Topological phases of matter primarily occur at zero temperature, as thermal fluctuations tend to destroy them and disrupt their underlying order. In a recent paper published in Physical Review Letters, however, researchers at Nanjing University, Yale University and other institutes reported a new 3D topological phase of matter characterized by an anomalous two-form symmetry that occurs at non-zero temperatures.

“In the last several years, we have made substantial progress in our ability to control —over a range of different platforms: , trapped ions, , photonics, and so on,” Tyler D. Ellison, senior author of the paper, told Phys.org.

Next-level pixel-particle analogy uses quantum-inspired math to clarify noisy medical images

Medical imaging methods such as ultrasound and MRI are often affected by background noise, which can introduce blurring and obscure fine anatomical details in the images. For clinicians who depend on medical images, background noise is a fundamental problem in making accurate diagnoses.

Methods for denoising have been developed with some success, but they struggle with the complexity of noise patterns in and require manual tuning of parameters, adding complexity to the denoising process.

To solve the denoising problem, some researchers have drawn inspiration from , which describes how matter and energy behave at the atomic scale. Their studies draw an analogy between how particles vibrate and how pixel intensity spreads out in images and causes noise. Until now, none of these attempts directly applied the full-scale mathematics of quantum mechanics to image denoising.

Room-Temperature Quantum Breakthrough Stuns Physicists

Scientists have achieved a breakthrough in quantum research by demonstrating that nanoparticles can exhibit quantum rotational vibrations even at room temperature — and without being cooled close to absolute zero. Using an elliptical nanoparticle held in an electromagnetic field, they applied car

Wave-like domain walls drive polarization switching in sliding ferroelectrics, study finds

Sliding ferroelectrics are a type of two-dimensional (2D) material realized by stacking nonpolar monolayers (atom-thick layers that lack an electric dipole). When these individual layers are stacked, they produce ferroelectric materials with an intrinsic polarization (i.e., in which positive and negative charges are spontaneously separated), which can be switched using an external electric field that is perpendicular to them.

Understanding the mechanisms driving the switching of this polarization in sliding ferroelectrics has been a key goal of many studies rooted in physics and materials science. This could ultimately inform the development of new advanced nanoscale electronics and quantum technologies.

Researchers at Westlake University and the University of Electronic Science and Technology of China recently uncovered a new mechanism that could drive the switching of polarization in sliding ferroelectrics. Their paper, published in Physical Review Letters (PRL), suggests that polarization switching in the materials is prompted by wave-like movements of domain walls (i.e., boundaries between regions with an opposite polarization), rather than by synchronized shifts affecting entire monolayers at once, as was assumed by some earlier works.

Powerful form of quantum interference paves the way for phonon-based technologies

Just as overlapping ripples on a pond can amplify or cancel each other out, waves of many kinds—including light, sound and atomic vibrations—can interfere with one another. At the quantum level, this kind of interference powers high-precision sensors and could be harnessed for quantum computing.

In a new study published in Science Advances, researchers at Rice University and collaborators have demonstrated a strong form of interference between phonons—the vibrations in a material’s structure that constitute the tiniest units (quanta) of heat or sound in that system. The phenomenon where two phonons with different frequency distributions interfere with each other, known as Fano resonance, was two orders of magnitude greater than any previously reported.

“While this phenomenon is well-studied for particles like electrons and photons, interference between phonons has been much less explored,” said Kunyan Zhang, a former postdoctoral researcher at Rice and first author on the study. “That is a missed opportunity, since phonons can maintain their wave behavior for a long time, making them promising for stable, high-performance devices.”

South Africa and China set up a quantum communication link: How we did it and why it’s historic

A major breakthrough in quantum technology was achieved in October 2024: the first-ever quantum satellite communication link between China and South Africa. The connection spanned a remarkable 12,900 km: the longest intercontinental quantum communication link established to date. The longest before this was 7,600 km and within the northern hemisphere only.

It was achieved with quantum , a method for a sender and receiver to share a secure key that they can use to safely send messages. Any interception during transmission leaves traces that can be detected. It involves sending single photons (tiny particles of light).

If someone tries to intercept the photons, the photons get disturbed because of quantum physics. Quantum physics is the study of matter and energy at the most fundamental level. Sender and receiver use only undisturbed photons, making the key to the message ultra secure. The key can be sent via optical fiber or free-space, including satellites.

Quantum dot technique improves multi-photon state generation

A photonics research group co-led by Gregor Weihs of the University of Innsbruck has developed a new technique for generating multi-photon states from quantum dots that overcomes the limitations of conventional approaches. This has immediate applications in secure quantum key distribution protocols, where it can enable simultaneous secure communication with different parties.

Quantum dots—semiconductor nanostructures that can emit on demand—are considered among the most promising sources for photonic quantum computing. However, every quantum dot is slightly different and may emit a slightly different color. This means that to produce multi-photon states, we cannot use multiple quantum dots.

Usually, researchers use a single quantum dot and multiplex the emission into different spatial and temporal modes, using a fast electro-optic modulator. The technological challenge is that faster electro-optic modulators are expensive and often require very customized engineering. To add to that, they may not be very efficient, which introduces unwanted losses into the system.

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