Computers Math

Researchers from Tel Aviv University have engineered the world’s tiniest technology, with a thickness of only two atoms. According to the researchers, the new technology proposes a way for storing electric information in the thinnest unit known to science, in one of the most stable and inert materials in nature. The allowed quantum-mechanical electron tunneling through the atomically thin film may boost the information reading process much beyond current technologies.
The research was performed by scientists from the Raymond and Beverly Sackler School of Physics and Astronomy and Raymond and Beverly Sackler School of Chemistry. The group includes Maayan Vizner Stern, Yuval Waschitz, Dr. Wei Cao, Dr. Iftach Nevo, Prof. Eran Sela, Prof. Michael Urbakh, Prof. Oded Hod, and Dr. Moshe Ben Shalom. The work is now published in Science magazine.
“Our research stems from curiosity about the behavior of atoms and electrons in solid materials, which has generated many of the technologies supporting our modern way of life,” says Dr. Ben Shalom. “We (and many other scientists) try to understand, predict, and even control the fascinating properties of these particles as they condense into an ordered structure that we call a crystal. At the heart of the computer, for example, lies a tiny crystalline device designed to switch between two states indicating different responses — “yes” or “no,” “up” or “down” etc. Without this dichotomy — it is not possible to encode and process information. The practical challenge is to find a mechanism that would enable switching in a small, fast, and inexpensive device.
Current state-of-the-art devices consist of tiny crystals that contain only about a million atoms (about a hundred atoms in height, width, and thickness) so that a million of these devices can be squeezed about a million times into the area of one coin, with each device switching at a speed of about a million times per second.
Following the technological breakthrough, the researchers were able, for the first time, to reduce the thickness of the crystalline devices to two atoms only. Dr. Ben Shalom emphasizes that such a thin structure enables memories based on the quantum ability of electrons to hop quickly and efficiently through barriers that are just several atoms thick. Thus, it may significantly improve electronic devices in terms of speed, density, and energy consumption.
In the study, the researchers used a two-dimensional material: one-atom-thick layers of boron and nitrogen, arranged in a repetitive hexagonal structure. In their experiment, they were able to break the symmetry of this crystal by artificially assembling two such layers. “In its natural three-dimensional state, this material is made up of a large number of layers placed on top of each other, with each layer rotated 180 degrees relative to its neighbors (antiparallel configuration)” says Dr. Ben Shalom. “In the lab, we were able to artificially stack the layers in a parallel configuration with no rotation, which hypothetically places atoms of the same kind in perfect overlap despite the strong repulsive force between them (resulting from their identical charges). In actual fact, however, the crystal prefers to slide one layer slightly in relation to the other, so that only half of each layer’s atoms are in perfect overlap, and those that do overlap are of opposite charges — while all others are located above or below an empty space — the center of the hexagon. In this artificial stacking configuration the layers are quite distinct from one another. For example, if in the top layer only the boron atoms overlap, in the bottom layer it’s the other way around.”
Dr. Ben Shalom also highlights the work of the theory team, who conducted numerous computer simulations “Together we established deep understanding of why the system’s electrons arrange themselves just as we had measured in the lab. Thanks to this fundamental understanding, we expect fascinating responses in other symmetry-broken layered systems as well,” he says.
Maayan Wizner Stern, the PhD student who led the study, explains: “The symmetry breaking we created in the laboratory, which does not exist in the natural crystal, forces the electric charge to reorganize itself between the layers and generate a tiny internal electrical polarization perpendicular to the layer plane. When we apply an external electric field in the opposite direction the system slides laterally to switch the polarization orientation. The switched polarization remains stable even when the external field is shut down. In this the system is similar to thick three-dimensional ferroelectric systems, which are widely used in technology today.”
“The ability to force a crystalline and electronic arrangement in such a thin system, with unique polarization and inversion properties resulting from the weak Van der Waals forces between the layers, is not limited to the boron and nitrogen crystal,” adds Dr. Ben Shalom. “We expect the same behaviors in many layered crystals with the right symmetry properties. The concept of interlayer sliding as an original and efficient way to control advanced electronic devices is very promising, and we have named it Slide-Tronics.”
Maayan Vizner Stern concludes: “We are excited about discovering what can happen in other states we force upon nature and predict that other structures that couple additional degrees of freedom are possible. We hope that miniaturization and flipping through sliding will improve today’s electronic devices, and moreover, allow other original ways of controlling information in future devices. In addition to computer devices, we expect that this technology will contribute to detectors, energy storage and conversion, interaction with light, etc. Our challenge, as we see it, is to discover more crystals with new and slippery degrees of freedom.”
The study was funded through support from the European Research Council (ERC starting grant), the Israel Science Foundation (ISF), and the Ministry of Science and Technology (MOST). More

UCLA engineers have demonstrated successful integration of a novel semiconductor material into high-power computer chips to reduce heat on processors and improve their performance. The advance greatly increases energy efficiency in computers and enables heat removal beyond the best thermal-management devices currently available.
The research was led by Yongjie Hu, an associate professor of mechanical and aerospace engineering at the UCLA Samueli School of Engineering. Nature Electronics recently published the finding in this article.
Computer processors have shrunk down to nanometer scales over the years, with billions of transistors sitting on a single computer chip. While the increased number of transistors helps make computers faster and more powerful, it also generates more hot spots in a highly condensed space. Without an efficient way to dissipate heat during operation, computer processors slow down and result in unreliable and inefficient computing. In addition, the highly concentrated heat and soaring temperatures on computer chips require extra energy to prevent processers from overheating.
In order to solve the problem, Hu and his team had pioneered the development of a new ultrahigh thermal-management material in 2018. The researchers developed defect-free boron arsenide in their lab and found it to be much more effective in drawing and dissipating heat than other known metal or semiconductor materials such as diamond and silicon carbide. Now, for the first time, the team has successfully demonstrated the material’s effectiveness by integrating it into high-power devices.
In their experiments, the researchers used computer chips with state-of-the-art, wide bandgap transistors made of gallium nitride called high-electron-mobility transistors (HEMTs). When running the processors at near maximum capacity, chips that used boron arsenide as a heat spreader showed a maximum heat increase from room temperatures to nearly 188 degrees Fahrenheit. This is significantly lower than chips using diamond to spread heat, with temperatures rising to approximately 278 degrees Fahrenheit, or the ones with silicon carbide showing a heat increase to about 332 degrees Fahrenheit.
“These results clearly show that boron-arsenide devices can sustain much higher operation power than processors using traditional thermal-management materials,” Hu said. “And our experiments were done under conditions where most current technologies would fail. This development represents a new benchmark performance and shows great potential for applications in high-power electronics and future electronics packaging.”
According to Hu, boron arsenide is ideal for heat management because it not only exhibits excellent thermal conductivity but also displays low heat-transport resistance.
“When heat crosses a boundary from one material to another, there’s typically some slowdown to get into the next material,” Hu said. “The key feature in our boron arsenide material is its very low thermal- boundary resistance. This is sort of like if the heat just needs to step over a curb, versus jumping a hurdle.”
The team has also developed boron phosphide as another excellent heat-spreader candidate. During their experiments, the researchers first illustrated the way to build a semiconductor structure using boron arsenide and then integrated the material into a HEMT-chip design. The successful demonstration opens up a path for industry adoption of the technology.
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Knowing the weight of a commodity provides an objective way to value goods in the marketplace. But did a self-regulating market even exist in the Bronze Age? And what can weight systems tell us about this? A team of researchers from the University of Göttingen researched this by investigating the dissemination of weight systems throughout Western Eurasia. Their new simulation indicates that the interaction of merchants, even without substantial intervention from governments or institutions, is likely to explain the spread of Bronze Age technology to weigh goods. The results were published in Proceedings of the National Academy of Sciences (PNAS).
To determine how different units of weight emerged in different regions, researchers compared all the weight systems in use between Western Europe and the Indus Valley from 3,000-1,000 BC. Analysis of 2,274 balance weights from 127 sites revealed that, with the exception of those from the Indus Valley, new and very similar units of weight appeared in a gradual spread west of Mesopotamia. To find out if the gradual formation of these systems could be due to propagation of error from a single weight system, the researchers modelled the creation of 100 new units. Taking into account factors such as measurement error, the simulation supported a single origin between Mesopotamia and Europe. It also showed that the Indus Valley probably developed an independent weight system. The research demonstrated that if information flow in Eurasia trade was free enough to support a common weight system, it was likely to be sufficient to react to local price fluctuations.
The weight systems that emerged between Mesopotamia and Europe were very similar. This meant that a single merchant could travel, for instance, from Mesopotamia to the Aegean and from there to Central Europe and never need to change their own set of weights. The merchant could trade with foreign partners while simply relying on approximating the weights. There was no international authority that could have regulated the accuracy of weight systems over such a wide territory and long time span. In Europe, beyond the Aegean, centralised authorities did not even exist at this time. The researchers conclude that the emergence of accurate weight systems must have been the outcome of a global network regulating itself from the bottom-up.
“With the results of our statistical analysis and experimental tests, it is now possible to prove the long-held hypothesis that free entrepreneurship was already a primary driver of the world economy even as early as the Bronze Age,” explains Professor Lorenz Rahmstorf from the Institute for Prehistory and Early History, University of Göttingen. Merchants could interact freely, establish profitable partnerships, and take advantage of the opportunities offered by long-distance trade. “The idea of a self-regulating market existing some 4,000 years ago puts a new perspective on the global economy of the modern era,” says Dr Nicola Ialongo, University of Göttingen. He adds, “Try to imagine all the international institutions that currently regulate our modern world economy: is global trade possible thanks to these institutions, or in spite of them?”
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When you think about trade and market relationships, you might think about brokers yelling at each other on the floor of a stock exchange on Wall Street. But it seems one of the basic functions of a free market is quietly practiced by fungi.
New research from a Rice University economist suggests certain networks of fungi embrace an important economic theory as they engage in trading nutrients for carbon with their host plants. This finding could aid the understanding of carbon storage in soils, an important tool in mitigating climate change.
A research paper entitled “Walrasian equilibrium behavior in nature” is available online and will appear in an upcoming edition of Proceedings of the National Academy of Sciences. Ted Loch-Temzelides, a professor of economics and the George and Cynthia Mitchell Chair in Sustainable Development at Rice, examined through an economic lens data from ecological experiments on arbuscular mycorrhizal fungi networks, which connect to plants and facilitate the trading of nutrients for carbon.
Loch-Temzelides found that these relationships resemble how economists think about competitive — also known as Walrasian — markets. The paper demonstrates that Walrasian equilibrium, a leading concept in the economic theory of markets used to make predictions, can also be used to understand trade in this “biological market.”
“Far from being self-sacrificing, organisms such as fungi can exhibit competitive behavior similar to that in markets involving sophisticated human participants,” Loch-Temzelides said.
His finding also implies that resources are allocated to the maximum benefit of the market participants — in this case, fungi and plants.
“Mycorrhizal fungi networks around the world are estimated to sequester around 5 billion tons of carbon per year,” Loch-Temzelides said. “Manipulating the terms of trade so that carbon obtained from host plants becomes less expensive compared to nutrients could lead to additional carbon being stored in the soil, which could provide major benefits in fighting climate change.”
Loch-Temzelides hopes future research by biologists and economists can make progress on better understanding these interactions.
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Research from the McKelvey School of Engineering at Washington University in St. Louis has found a missing piece in the puzzle of optical quantum computing.
Jung-Tsung Shen, associate professor in the Preston M. Green Department of Electrical & Systems Engineering, has developed a deterministic, high-fidelity two-bit quantum logic gate that takes advantage of a new form of light. This new logic gate is orders of magnitude more efficient than the current technology.
“In the ideal case, the fidelity can be as high as 97%,” Shen said.
His research was published in May 2021 in the journal Physical Review A.
The potential of quantum computers is bound to the unusual properties of superposition — the ability of a quantum system to contain many distinct properties, or states, at the same time — and entanglement — two particles acting as if they are correlated in a non-classical manner, despite being physically removed from each other.
Where voltage determines the value of a bit (a 1 or a 0) in a classical computer, researchers often use individual electrons as “qubits,” the quantum equivalent. Electrons have several traits that suit them well to the task: they are easily manipulated by an electric or magnetic field and they interact with each other. Interaction is a benefit when you need two bits to be entangled — letting the wilderness of quantum mechanics manifest. More

University of Colorado Boulder researchers have discovered that minuscule, self-propelled particles called “nanoswimmers” can escape from mazes as much as 20 times faster than other, passive particles, paving the way for their use in everything from industrial clean-ups to medication delivery.
The findings, published this week in the Proceedings of the National Academy of Sciences, describe how these tiny synthetic nanorobots are incredibly effective at escaping cavities within maze-like environments. These nanoswimmers could one day be used to remediate contaminated soil, improve water filtration or even deliver drugs to targeted areas of the body, like within dense tissues.
“This is the discovery of an entirely new phenomenon that points to a broad potential range of applications,” said Daniel Schwartz, senior author of the paper and Glenn L. Murphy Endowed Professor of chemical and biological engineering.
These nanoswimmers came to the attention of the theoretical physics community about 20 years ago, and people imagined a wealth of real-world applications, according to Schwartz. But unfortunately these tangible applications have not yet been realized, in part because it’s been quite difficult to observe and model their movement in relevant environments — until now.
These nanoswimmers, also called Janus particles (named after a Roman two-headed god), are tiny spherical particles composed of polymer or silica, engineered with different chemical properties on each side of the sphere. One hemisphere promotes chemical reactions to occur, but not the other. This creates a chemical field which allows the particle to take energy from the environment and convert it into directional motion — also known as self-propulsion.
“In biology and living organisms, cell propulsion is the dominant mechanism that causes motion to occur, and yet, in engineered applications, it’s rarely used. Our work suggests that there is a lot we can do with self-propulsion,” said Schwartz. More

A recent proof-of-concept study finds that a low-cost training program can reduce hazardous driving in older adults. Researchers hope the finding will lead to the training becoming more widely available.
“On-road training and simulator training programs have been successful at reducing car accidents involving older drivers — with benefits lasting for years after the training,” says Jing Yuan, first author of the study and a Ph.D. student at North Carolina State University. “However, many older adults are unlikely to have access to these training programs or technologies.”
“We developed a training program, called Drive Aware, that would be accessible to anyone who has a computer,” says Jing Feng, corresponding author of the study and a professor of psychology at NC State. “Specifically, Drive Aware is a cognitive training program for older adults to help them accurately detect road hazards. The goal of our recent study was to determine the extent to which Drive Aware influences driving behaviors when trainees actually get behind the wheel.”
To test Drive Aware, the researchers enlisted 27 adults, ages 65 and older. All of the study participants took a baseline driving test in a driving simulator. Nine of the study participants were then placed in the “active training” group. The active training group received two interactive Drive Aware training sessions, about a week apart. Nine other study participants were placed in a “passive training” group. This group watched video of other people receiving the Drive Aware training sessions. This took place twice, with sessions about a week apart. The remaining nine study participants served as the control group and received no training. All 27 study participants then took a second driving test in the driving simulator.
The researchers found that study participants who were part of the active training group had 25% fewer “unsafe incidents” after the training. Unsafe incidents included accidents with other vehicles, pedestrians, running off the road, etc. There was no statistically significant change in the number of unsafe incidents for study participants in the passive training group or the control group.
“In short, we found that older adults were less likely to have an accident in the driving simulator after receiving the Drive Aware training,” Yuan says.
“This testing was done with a fairly modest number of study participants,” Feng says. “If we can secure the funding, we’d like to scale up our testing to more clearly establish how effective this training is at reducing accidents among older drivers. If the results are as good as they look right now, we’d want to find ways to share the training program as broadly as possible. Not many people can afford one-on-one on-the-road training, or training that involves high-end driving simulators. But we think a lot of people would be able to access Drive Aware, and it has the potential to save a lot of lives.”
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Materials provided by North Carolina State University. Original written by Matt Shipman. Note: Content may be edited for style and length. More

The electronic properties of graphene can be specifically modified by stretching the material evenly, say researchers at the University of Basel. These results open the door to the development of new types of electronic components.
Graphene consists of a single layer of carbon atoms arranged in a hexagonal lattice. The material is very flexible and has excellent electronic properties, making it attractive for numerous applications — electronic components in particular.
Researchers led by Professor Christian Schönenberger at the Swiss Nanoscience Institute and the Department of Physics at the University of Basel have now studied how the material’s electronic properties can be manipulated by mechanical stretching. In order to do this, they developed a kind of rack by which they stretch the atomically thin graphene layer in a controlled manner, while measuring its electronic properties.
Sandwiches on the rack
The scientists first prepared a “sandwich” comprising a layer of graphene between two layers of boron nitride. This stack of layers, furnished with electrical contacts, was placed on a flexible substrate.
The researchers then applied a force to the center of the sandwich from below using a wedge. “This enabled us to bend the stack in a controlled way, and to elongate the entire graphene layer,” explained lead author Dr. Lujun Wang.
“Stretching the graphene allowed us to specifically change the distance between the carbon atoms, and thus their binding energy,” added Dr. Andreas Baumgartner, who supervised the experiment.
Altered electronic states
The researchers first calibrated the stretching of the graphene using optical methods. They then used electrical transport measurements to study how the deformation of the graphene changes the electronic energies. The measurements need to be performed at minus 269°C for the energy changes to become visible.
“The distance between the atomic nuclei directly influences the properties of the electronic states in graphene,” said Baumgartner, summarizing the results. “With uniform stretching, only the electron velocity and energy can change. The energy change is essentially the ‘scalar potential’ predicted by theory, which we have now been able to demonstrate experimentally.”
These results could lead, for example, to the development of new sensors or new types of transistors. In addition, graphene serves as a model system for other two-dimensional materials that have become an important research topic worldwide in recent years.
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