Computers Math

Jamie Paik and her team of researchers at EPFL’s School of Engineering have created an origami-like robot that can change shape, move around and interact with objects and people.
By combining inspiration from the digital world of polygon meshing and the biological world of swarm behavior, the Mori3 robot can morph from 2D triangles into almost any 3D object. The EPFL research, which has been published in Nature Machine Intelligence, shows the promise of modular robotics for space travel. “Our aim with Mori3 is to create a modular, origami-like robot that can be assembled and disassembled at will depending on the environment and task at hand,” says Jamie Paik, director of the Reconfigurable Robotics Lab. “Mori3 can change its size, shape and function.”
A polygon robot
The individual modules of the Mori3 robot are triangular in shape. The modules easily join together to create polygons of different sizes and configurations in a process known as polygon meshing. “We have shown that polygon meshing is a viable robotic strategy,” says Christoph Belke, a Post-doctoral researcher in robotics. To achieve this, the team had to push the boundaries of various aspects of robotics, including the mechanical and electronic design, computer systems and engineering. “We had to rethink the way we understand robotics,” explains Belke. “These robots can change their own shape, attach to each other, communicate and reconfigure to form functional and articulated structures.” This proof of concept is a success as Mori3 robots are good at doing the three things that robots should be able to do: moving around, handling and transporting objects, and interacting with users.
Destined for space
What is the advantage in creating modular and multi-functional robots? Paik explains that, to perform a wide range of tasks, robots need to be able to change their shape or configuration. “Polygonal and polymorphic robots that connect to one another to create articulated structures can be used effectively for a variety of applications,” she says. “Of course, a general-purpose robot like Mori3 will be less effective than specialized robots in certain areas. That said, Mori3’s biggest selling point is its versatility.” Mori3 robots were designed in part to be used in spacecraft, which don’t have the room to store different robots for each individual task that needs to be carried out. The researchers hope that Mori3 robots will be used for communication purposes and external repairs. More

Everyday materials such as paper and plastic could be transformed into electronic “smart devices” by using a simple new method to apply liquid metal to surfaces, according to scientists in Beijing, China. The study, published June 9 in the journal Cell Reports Physical Science, demonstrates a technique for applying a liquid metal coating to surfaces that do not easily bond with liquid metal. The approach is designed to work at a large scale and may have applications in wearable testing platforms, flexible devices, and soft robotics.
“Before, we thought that it was impossible for liquid metal to adhere to non-wetting surfaces so easily, but here it can adhere to various surfaces only by adjusting the pressure, which is very interesting,” said Bo Yuan, a scientist at Tsinghua University and the first author of the study.
Scientists seeking to combine liquid metal with traditional materials have been impeded by liquid metal’s extremely high surface tension, which prevents it from binding with most materials, including paper. To overcome this issue, previous research has mainly focused on a technique called “transfer printing,” which involves using a third material to bind the liquid metal to the surface. But this strategy comes with drawbacks — adding more materials can complicate the process and may weaken the end product’s electrical, thermal, or mechanical performance.
To explore an alternative approach that would allow them to directly print liquid metal on substrates without sacrificing the metal’s properties, Yuan and colleagues applied two different liquid metals (eGaln and BilnSn) to various silicone and silicone polymer stamps, then applied different forces as they rubbed the stamps onto paper surfaces.
“At first, it was hard to realize stable adhesion of the liquid metal coating on the substrate,” said Yuan. “However, after a lot of trial and error, we finally had the right parameters to achieve stable, repeatable adhesion.”
The researchers found that rubbing the liquid metal-covered stamp against the paper with a small amount of force enabled the metal droplets to bind effectively to the surface, while applying larger amounts of force prevented the droplets from staying in place.
Next, the team folded the metal-coated paper into a paper crane, demonstrating that the surface can still be folded as usual after the process is completed. And after doing so, the modified paper still maintains its usual properties.
While the technique appears promising, Yuan noted that the researchers are still figuring out how to guarantee that the liquid metal coating stays in place after it has been applied. For now, a packaging material can be added to the paper’s surface, but the team hopes to figure out a solution that won’t require it.
“Just like wet ink on paper can be wiped off by hand, the liquid metal coating without packaging here also can be wiped off by the object it touches as it is applied,” said Yuan. “The properties of the coating itself will not be greatly affected, but objects in contact may be soiled.”
In the future, the team also plans to build on the method so that it can be used to apply liquid metal to a greater variety of surfaces, including metal and ceramic.
“We also plan to construct smart devices using materials treated by this method,” said Yuan.
This work was supported by China Postdoctoral Science Foundation, the National Nature Science Foundation of China, and the cooperation funding between Nanshan and Tsinghua SIGS in science and technology. More

When we communicate with others over wireless networks, information is sent to data centers where it is collected, stored, processed, and distributed. As computational energy usage continues to grow, it is on pace to potentially become the leading source of energy consumption in this century. Memory and logic are physically separated in most modern computers, and therefore the interaction between these two components is very energy intensive in accessing, manipulating, and re-storing data. A team of researchers from Carnegie Mellon University and Penn State University is exploring materials that could possibly lead to the integration of the memory directly on top of the transistor. By changing the architecture of the microcircuit, processors could be much more efficient and consume less energy. In addition to creating proximity between these components, the nonvolatile materials studied have the potential to eliminate the need for computer memory systems to be refreshed regularly.
Their recent work published in Science explores materials that are ferroelectric, or have a spontaneous electric polarization that can be reversed by the application of an external electric field. Recently discovered wurtzite ferroelectrics, which are mainly composed of materials that are already incorporated in semiconductor technology for integrated circuits, allow for the integration of new power-efficient devices for applications such as non-volatile memory, electro-optics, and energy harvesting. One of the biggest challenges of wurtzite ferroelectrics is that the gap between the electric fields required for operation and the breakdown field is very small.
“Significant efforts are devoted to increasing this margin, which demands a thorough understanding of the effect of films’ composition, structure, and architecture on the polarization switching ability at practical electric fields,” said Carnegie Mellon post-doctoral researcher Sebastian Calderon, who is the lead author of the paper.
The two institutions were brought together to collaborate on this study through the Center for 3D Ferroelectric Microelectronics (3DFeM), which is an Energy Frontier Research Center (EFRC) program led by Penn State University through funding from the U.S. Department of Energy’s (DOE) office of Basic Energy Science (BES).
Carnegie Mellon’s materials science and engineering department, led by Professor Elizabeth Dickey, was tapped for this project because of its background in studying the role of the structure of materials in the functional properties at very small scales through electron microscopy.
“Professor Dickey’s group brings a particular topical expertise in measuring the structure of these materials at very small length scales, as well as a focus on the particular electronic materials of interest of this project,” said Jon-Paul Maria, professor of Materials Science and Engineering at Penn State University.
Together, the research team designed an experiment combining the strong expertise of both institutions on the synthesis, characterization and theoretical modeling of wurtzite ferroelectrics. By observing and quantifying real-time polarization switching using scanning transmission electron microscopy (STEM), the study resulted in a fundamental understanding of how such novel ferroelectric materials switch at the atomic level. As research in this area progresses, the goal is to scale the materials to a size in which they can be used in modern microelectronics.
This material is based upon work supported by the center for 3D Ferroelectric Microelectronics (3DFeM), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences Energy Frontier Research Centers program under Award Number DE-SC0021118. More

3D integrated circuits are a key part of improving the efficiency of electronics to meet the considerable demands of consumers. They are constantly being developed, but translating theoretical findings into actual devices is not easy. Now, a new design by a research team from Japan can turn these theories into reality.
In a study recently published for the VLSI Symposium 2023, researchers from Institute of Industrial Science, The University of Tokyo have reported a deposition process for nanosheet oxide semiconductor. The oxide semiconductor resulting from this process has high carrier mobility and reliability in transistors.
3D integrated circuits are made up of multiple layers that each play a role in the overall function. Oxide semiconductors are attracting a lot of attention as materials for various circuit components because they can be processed at low temperature, while still having high carrier mobility and low charge leakage, and are able to withstand high voltages.
There are also advantages to using oxides rather than metals in processes where electrodes may be exposed to oxygen during the integration process and become oxidized.
However, developing the processes needed to reliably deposit very thin layers of oxide semiconductor materials in the manufacture of devices is challenging and has not been fully established to date. Recently, the researchers have reported an atomic layer deposition (ALD) technique that produces layers appropriate for large-scale integration.
“Using our process, we carried out a systematic study of field effect transistors (FETs) to establish their limitations and optimize their properties,” explains lead author of the study, Kaito Hikake. FETs control the current flow in a semiconductor. “We tuned the ratio of the components and adjusted the preparation conditions and our findings led to the development of a multi-gate nanosheet FET for normally-off operation and high reliability.”
The findings revealed that a FET made from the chosen oxide semiconductor by ALD had the best performance. The multi-gate nanosheet FET is believed to be the first to combine high carrier mobility and reliability characteristics with normally-off operation.
“In rapidly moving areas such as electronics, it is important to translate proof of concept findings into industrially relevant processes,” says Masaharu Kobayashi, senior author. “We believe that our study provides a robust technique that can be used to produce devices that meet the market’s need for manufacturable 3D integrated circuits with high function.”
The findings in this study have provided a solution to one of the big obstacles in the manufacturing of electronic devices with semiconductors. Hopefully, this will bring more designs of electronics with high functionality to actual products. More

A group of researchers from Tohoku University has unveiled a new material that exhibits enormous magnetoresistance, paving the way for developments in non-volatile magnetoresistive memory (MRAM).
Details of their unique discovery were published in the Journal of Alloys and Compounds on May 29, 2023.
Today, the demand for advancements in hardware that can efficiently process large amounts of digital information and in sensors has never been greater, especially with governments deploying technological innovations to achieve smarter societies.
Much of this hardware and sensors rely on MRAM and magnetic sensors, and tunnel magnetoresistive devices make up the majority of such devices.
Tunnel magnetoresistive devices exploit the tunnel magnetoresistance effect to detect and measure magnetic fields. This is tied to the magnetization of ferromagnetic layers in magnetic tunnel junctions. When the magnets are aligned, a low resistance state is observed, and electrons can easily tunnel through the thin insulating barrier between them. When the magnets are not aligned, the tunneling of electrons becomes less efficient and leads to higher resistance. This change in resistance is expressed as the magnetoresistive ratio, a key figure in determining the efficiency of tunneling magnetoresistive devices. The higher the magnetoresistance ratio, the better the device is.
Current tunnel magnetoresistive devices comprise magnesium oxide and iron-based magnetic alloys, like iron-cobalt. Iron-based alloys have a body-centered cubic crystal structure in ambient conditions and exhibit a huge tunnel magnetoresistance effect in devices with a rock salt-type magnesium oxide.

There have been two notable studies using these iron-based alloys that produced magnetoresistive devices displaying high magnetoresistance ratios. The first in 2004 was by the National Institute of Advanced Industrial Science and Technology in Japan and IBM; and the second came in 2008, when researchers from Tohoku University reported on a magnetoresistance ratio exceeding 600% at room temperature, something that jumped to 1000% with temperatures near zero kelvin.
Since those breakthroughs, various institutes and companies have invested considerable effort in honing device physics, materials, and processes. Yet aside from iron-based alloys, only some Heusler-type ordered magnetic alloys have displayed such enormous magnetoresistance.
Dr. Tomohiro Ichinose and Professor Shigemi Mizukami from Tohoku University recently began exploring thermodynamically metastable materials to develop a new material capable of demonstrating similar magnetoresistance ratios. To do so, they focused on the strong magnetic properties of cobalt-manganese alloys, which have a body-centered cubic metastable crystal structure.
“Cobalt-manganese alloys have face-centered cubic or hexagonal crystal structures as thermodynamically stable phases. Because this stable phase exhibits weak magnetism, it has never been studied as a practical material for tunnel magnetoresistive devices,” said Mizukami.
Back in 2020, the group reported on a device that used a cobalt-manganese alloy with metastable body-centered cubic crystal structure.
Using data science and/or high-throughput experimental methods, they built upon this discovery, and succeeded in obtaining huge magnetoresistance in devices by adding a small amount of iron to the metastable body-centered cubic cobalt-manganese alloy. The magnetoresistance ratio was 350% at room temperature and also exceeded 1000% at a low temperature. Additionally, the device fabrication employed the sputtering method and a heating process, something compatible with current industries.
“We have produced the third instance of a new magnetic alloy for tunneling magnetoresistive devices showing huge magnetoresistance, and it sets an alternative direction of travel for future improvements,” adds Mizukami. More

The patterns of light hold tremendous promise for a large encoding alphabet in optical communications, but progress is hindered by their susceptibility to distortion, such as in atmospheric turbulence or in bent optical fibre.  Now researchers at the University of the Witwatersrand (Wits) have outlined a new optical communication protocol that exploits spatial patterns of light for multi-dimensional encoding in a manner that does not require the patterns to be recognised, thus overcoming the prior limitation of modal distortion in noisy channels.  The result is a new encoding state-of-the-art of over 50 vectorial patterns of light sent virtually noise-free across a turbulent atmosphere, opening a new approach to high-bit-rate optical communication.  Published this week in Laser & Photonics Reviews, the Wits team from the Structured Light Laboratory in the Wits School of Physics used a new invariant property of vectorial light to encode information.  This quantity, which the team call “vectorness”, scales from 0 to 1 and remains unchanged when passing through a noisy channel.  Unlike traditional amplitude modulation which is 0 or 1 (only a two-letter alphabet), the team used the invariance to partition the 0 to 1 vectorness range into more than 50 parts (0, 0.02, 0.04 and so on up to 1) for a 50-letter alphabet.  Because the channel over which the information is sent does not distort the vectorness, both sender and received will always agree on the value, hence noise-free information transfer.  The critical hurdle that the team overcame is to use patterns of light in a manner that does not require them to be “recognised”, so that the natural distortion of noisy channels can be ignored.  Instead, the invariant quantity just “adds up” light in specialised measurements, revealing a quantity that doesn’t see the distortion at all.“This is a very exciting advance because we can finally exploit the many patterns of light as an encoding alphabet without worrying about how noisy the channel is,” says Professor Andrew Forbes, from the Wits School of Physics. “In fact, the only limit to how big the alphabet can be is how good the detectors are and not at all influenced by the noise of the channel.”Lead author and PhD candidate Keshaan Singh adds: “To create and detect the vectorness modulation requires nothing more than conventional communications technology, allowing our modal (pattern) based protocol to be deployed immediately in real-world settings.”The team have already started demonstrations in optical fibre and in fast links across free-space, and believe that the approach can work in other noisy channels, including underwater. More

A central difficulty in controlling greenhouse gas emissions to slow down climate change is finding them in the first place.
Such is the case with methane, a colorless, odorless gas that is the second most abundant greenhouse gas in the atmosphere today, after carbon dioxide. Although it has a shorter life than carbon dioxide, according to the U.S. Environmental Protection Agency, it’s more than 25 times as potent as CO2 at trapping heat, and is estimated to trap 80 times more heat in the atmosphere than CO2 over 20 years.
For that reason, curbing methane has become a priority, said UC Santa Barbara researcher Satish Kumar, a doctoral student in the Vision Research Lab of computer scientist B.S. Manjunath.
“Recently, at the 2022 International Climate Summit, methane was actually the highlight because everybody is struggling with it,” he said.
Even with reporting requirements in the U.S., methane’s invisibility means that its emissions are likely going underreported. In some cases the discrepancies are vast, such as with the Permian Basin, an 86,000-square-mile oil and natural gas extraction field located in Texas and New Mexico that hosts tens of thousands of wells. Independent methane monitoring of the area has revealed that the site emits eight to 10 times more methane than reported by the field’s operators.
In the wake of the COP27 meetings, the U.S. government is now seeking ways to tighten controls over these types of “super emitting” leaks, especially as oil and gas production is expected to increase in the country in the near future. To do so, however, there must be a way of gathering reliable fugitive emissions data in order to assess the oil and gas operators’ performance and levy appropriate penalties as needed.

Enter MethaneMapper, an artificial intelligence-powered hyperspectral imaging tool that Kumar and colleagues have developed to detect real-time methane emissions and trace them to their sources. The tool works by processing hyperspectral data gathered during overhead, airborne scans of the target area.
“We have 432 channels,” Kumar said. Using survey images from NASA’s Jet Propulsion Laboratory, the researchers take pictures starting from 400 nanometer wavelengths, and at intervals up to 2,500 nanometers — a range that encompasses the spectral signatures of hydrocarbons, including that of methane. Each pixel in the photograph contains a spectrum and represents a range of wavelengths called a “spectral band.” From there, machine learning takes on the huge amount of data to differentiate methane from other hydrocarbons captured in the imaging process. The method also allows users to see not just the magnitude of the plume, but also its source.
Hyperspectral imaging for methane detection is a hot field, with companies jumping into the fray with equipment and detection systems. What makes MethaneMapper stand out is the diversity and depth of data collected from various types of terrain that allows the machine learning model to pick out the presence of methane against a backdrop of different topographies, foliage and other backgrounds.
“A very common problem with the remote sensing community is that whatever is designed for one place won’t work outside that place,” Kumar explained. Thus, a remote sensing program will often learn what methane looks like against a certain landscape — say, the dry desert of the American Southwest — but pit it against the rocky shale of Colorado or the flat expanses of the Midwest, and the system might not be as successful.
“We curated our own data sets, which cover approximately 4,000 emissions sites,” Kumar said. “We have the dry states of California, Texas and Arizona. But we have the dense vegetation of the state of Virginia too. So it’s pretty diverse.” According to him, MethaneMapper’s performance accuracy currently stands at 91%.

The current operating version of MethaneMapper relies on airplanes for the scanning component of the system. But the researchers are setting some ambitious sights for a satellite-enabled program, which has the potential to scan wider swaths of terrain repeatedly, without the greenhouse gasses that airplanes emit. The major tradeoff between using planes and using satellites is in the resolution, Kumar said.
“You can detect emissions as small as 50 kg per hour from an airplane,” he said. With a satellite, the threshold increases to about 1000 kg or 1 ton per hour. But for the purpose of monitoring emissions from oil and gas operations, which tend to emit in the thousands of kilograms per hour, it’s a small price to pay for the ability to scan larger parts of the Earth, and in places that might not be on the radar, so to speak.
“The most recent case, I think seven or eight months ago, were emissions from an oil rig off the coast somewhere toward Mexico,” Kumar said, “which was emitting methane at a rate of 7,610 kilograms per hour for six months. And nobody knew about it.
“And methane is so dangerous,” he continued. “The amount of damage that carbon dioxide will do in a hundred years, methane can do in only 1.2 years.” Satellite detection could not only track carbon emissions on the global scale, it can also be used to direct subsequent airplane-based scans for higher-resolution investigations.
Ultimately, Kumar and colleagues want to bring the power of AI and hyperspectral methane imaging to the mainstream, making it available to a wide variety of users even without expertise in machine learning.
“What we want to provide is an interface through a web platform such as BisQue, where anyone can click and upload their data and it can generate an analysis,” he said. “I want to provide a simple and effective interface that anyone can use.”
The MethaneMapper project is funded by National Science Foundation award SI2-SSI #1664172. The project is part of the Center for Multimodal Big Data Science and Healthcare initiative at UC Santa Barbara, led by Prof. B.S. Manjunath. Additionally, MethaneMapper will be featured as a Highlight Paper at the 2023 Computer Vision and Pattern Recognition (CVPR) Conference — the premiere event in the computer vision field — to be held June 18-22 in Vancouver, British Columbia. More

Quantum computing uses the principles of quantum mechanics to encode and elaborate data, meaning that it could one day solve computational problems that are intractable with current computers. While the latter work with bits, which represent either a 0 or a 1, quantum computers use quantum bits, or qubits — the fundamental units of quantum information.
“With applications ranging from drug discovery to optimization and simulations of complex biological systems and materials, quantum computing has the potential to reshape vast areas of science, industry, and society,” says Professor Vincenzo Savona, director of the Center for Quantum Science and Engineering at EPFL.
Unlike classical bits, qubits can exist in a “superposition” of both 0 and 1 states at the same time. This allows quantum computers to explore multiple solutions simultaneously, which could make them significantly faster in certain computational tasks. However, quantum systems are delicate and susceptible to errors caused by interactions with their environment.
“Developing strategies to either protect or qubits from this or to detect and correct errors once they have occurred is crucial for enabling the development of large-scale, fault-tolerant quantum computers,” says Savona. Together with EPFL physicists Luca Gravina, and Fabrizio Minganti, they have made a significant breakthrough by proposing a “critical Schrödinger cat code” for advanced resilience to errors. The study introduces a novel encoding scheme that could revolutionize the reliability of quantum computers.
What is a “critical Schrödinger cat code”?
In 1935, physicist Erwin Schrödinger proposed a thought experiment as a critique of the prevailing understanding of quantum mechanics at the time — the Copenhagen interpretation. In Schrödinger’s experiment, a cat is placed in a sealed box with a flask of poison and a radioactive source. If a single atom of the radioactive source decays, the radioactivity is detected by a Geiger counter, which then shatters the flask. The poison is released, killing the cat.
According to the Copenhagen view of quantum mechanics, if the atom is initially in superposition, the cat will inherit the same state and find itself in a superposition of alive and dead. “This state represents exactly the notion of a quantum bit, realized at the macroscopic scale,” says Savona.
In past years, scientists have drawn inspiration by Schrödinger’s cat to build an encoding technique called “Schrödinger’s cat code.” Here, the 0 and 1 states of the qubit are encoded onto two opposite phases of an oscillating electromagnetic field in a resonant cavity, similarly to the dead or alive states of the cat.
“Schrödinger cat codes have been realized in the past using two distinct approaches,” explains Savona. “One leverages anharmonic effects in the cavity, the other relying on carefully engineered cavity losses. In our work, we bridged the two by operating in an intermediate regime, combining the best of both worlds. Although previously believed to be unfruitful, this hybrid regime results in enhanced error suppression capabilities.” The core idea is to operate close to the critical point of a phase transition, which is what the ‘critical’ part of the critical cat code refers to.
The critical cat code has an additional advantage: it exhibits exceptional resistance to errors that result from random frequency shifts, which often pose significant challenges to operations involving multiple qubits. This solves a major problem and paves the way to the realization of devices with several mutually interacting qubits — the minimal requirement for building a quantum computer.
“We are taming the quantum cat,” says Savona. “By operating in a hybrid regime, we have developed a system that surpasses its predecessors, which represents a significant leap forward for cat qubits and quantum computing as a whole. The study is a milestone on the road towards building better quantum computers, and showcases EPFL’s dedication in advancing the field of quantum science and unlocking the true potential of quantum technologies. More