Aurelia Butler

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    Simple hand-built structures can help streams survive wildfires and drought

    Wearing waders and work gloves, three dozen employees from the U.S. Department of Agriculture’s Natural Resources Conservation Service stood at a small creek amid the dry sagebrush of southeastern Idaho. The group was eager to learn how to repair a stream the old­-fashioned way.

    Tipping back his white cowboy hat, 73-year-old rancher Jay Wilde told the group that he grew up swimming and fishing at this place, Birch Creek, all summer long. But when he took over the family farm from his parents in 1995, the stream was dry by mid-June.

    Wilde realized this was partly because his family and neighbors, like generations of American settlers before them, had trapped and removed most of the dam-building beavers. The settlers also built roads, cut trees, mined streams, overgrazed livestock and created flood-control and irrigation structures, all of which changed the plumbing of watersheds like Birch Creek’s.

    Many of the wetlands in the western United States have disappeared since the 1700s. California has lost an astonishing 90 percent of its wetlands, which includes streamsides, wet meadows and ponds. In Nevada, Idaho and Colorado, more than 50 percent of wetlands have vanished. Precious wet habitats now make up just 2 percent of the arid West — and those remaining wet places are struggling.

    Nearly half of U.S. streams are in poor condition, unable to fully sustain wildlife and people, says Jeremy Maestas, a sagebrush ecosystem specialist with the NRCS who organized that workshop on Wilde’s ranch in 2016. As communities in the American West face increasing water shortages, more frequent and larger wildfires (SN: 9/26/20, p. 12) and unpredictable floods, restoring ailing waterways is becoming a necessity.

    Staff from the USDA Natural Resources Conservation Service pound posts to build a beaver dam analog across Birch Creek in Idaho in 2016. The effort gave nine relocated beavers a head start to create their own dam complexes.J. Maestas/USDA NRCS

    Landowners and conservation groups are bringing in teams of volunteers and workers, like the NRCS group, to build low-cost solutions from sticks and stones. And the work is making a difference. Streams are running longer into the summer, beavers and other animals are returning, and a study last December confirmed that landscapes irrigated by beaver activity can resist wildfires.

    Filling the sponge

    Think of a floodplain as a sponge: Each spring, floodplains in the West soak up snow melting from the mountains. The sponge is then wrung out during summer and fall, when the snow is gone and rainfall is scarce. The more water that stays in the sponge, the longer streams can flow and plants can thrive. A full sponge makes the landscape better equipped to handle natural disasters, since wet places full of green vegetation can slow floods, tolerate droughts or stall flames.

    Typical modern-day stream and river restoration methods can cost about $500,000 per mile, says Joseph Wheaton, a geomorphologist at Utah State University in Logan. Projects are often complex, and involve excavators and bulldozers to shore up streambanks using giant boulders or to construct brand-new channels.

    “Even though we spend at least $15 billion per year repairing waterways in the U.S., we’re hardly scratching the surface of what needs fixing,” Wheaton says.

    Big yellow machines are certainly necessary for restoring big rivers. But 90 percent of all U.S. waterways are small streams, the kind you can hop over or wade across.

    For smaller streams, hand-built restoration solutions work well, often at one-tenth the cost, Wheaton says, and can be self-sustaining once nature takes over. These low-tech approaches include building beaver dam analogs to entice beavers to stay and get to work, erecting small rock dams or strategically mounding mud and branches in a stream. The goal of these simple structures is to slow the flow of water and spread it across the floodplain to help plants grow and to fill the underground sponge.

    Less than a year after workers installed this hand-built rock structure, called a Zuni bowl, in an intermittent stream in southwestern Montana, erosion stopped moving upstream, keeping the grass above the structure green and lush.Sean Claffey/Southwest Montana Sagebrush Partnership

    Fixes like these help cure a common ailment that afflicts most streams out West, including Birch Creek, Wheaton says: Human activities have altered these waterways into straightened channels largely devoid of debris. As a result, most riverscapes flow too straight and too fast.

    “They should be messy and inefficient,” he says. “They need more structure, whether it’s wood, rock, roots or dirt. That’s what slows down the water.” Wheaton prefers the term “riverscape” over stream or river because he “can’t imagine a healthy river without including the land around it.”

    Natural structures “feed the stream a healthy diet” of natural materials, allowing soil and water to accumulate again in the floodplain, he says.

    Since as much as 75 percent of water resources in the West are on private land, conservation groups and government agencies like the NRCS are helping ranchers and farmers improve the streams, springs or wet meadows on their property.

    “In the West, water is life,” Maestas says. “But it’s a very time-limited resource. We’re trying to keep what we have on the landscape as long as possible.”

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    Beaver benefits

    In watersheds across the West, beavers can be a big part of filling the floodplain’s sponge. The rodents gnaw down trees to create lodges and dams, and dig channels for transporting their logs to the dams. All this work slows down and spreads out the water.

    On two creeks in northeastern Nevada, streamsides near beaver dams were up to 88 percent greener than undammed stream sections when measured from 2013 to 2016. Even better, beaver ponds helped maintain lush vegetation during the hottest summer months, even during a multiyear drought, Emily Fairfax, an ecohydrologist at California State University Channel Islands, and geologist Eric Small of University of Colorado Boulder reported in 2018 in Ecohydrology.

    Satellite images show that when beavers settled into one part of Nevada’s Maggie Creek (bottom), digging channels to ferry in logs to build dams, the floodplain was wider, wetter and greener than an area of the creek with no dams (top).E. Fairfax/CSU Channel Islands

    Satellite images show that when beavers settled into one part of Nevada’s Maggie Creek (bottom), digging channels to ferry in logs to build dams, the floodplain was wider, wetter and greener than an area of the creek with no dams (top).E. Fairfax/CSU Channel Islands

    “Bringing beavers back just makes good common sense when you get down to the science of it,” Wilde says. He did it on his ranch.

    Using beavers to restore watersheds is not a new idea. In 1948, for instance, Idaho Fish and Game biologists parachuted beavers out of airplanes, partly to improve trout habitat on public lands.

    Wilde used trucks instead of parachutes. In 2015 and 2016, he partnered with the U.S. Forest Service and Idaho Fish and Game to livetrap and relocate nine beavers to Birch Creek from public lands about 120 kilometers away. To ensure the released rodents had a few initial ponds where they could escape from predators, Wilde worked with Anabranch Solutions, a riverscape restoration company cofounded by Wheaton and colleagues, to construct 26 beaver dam analogs. Would these simple branch-and-post structures entice the beavers to stay in Birch Creek?

    It worked like a charm. In just three years, those beavers built 149 dams, transforming the once-narrow strip of green along the stream into a wide, vibrant floodplain. Birch Creek flowed 42 days longer, through the hottest part of the summer. Fish rebounded quickly too: Native Bonneville cutthroat trout populations were up to 50 times as abundant in the ponded sections in 2019 as they were when surveyed by the U.S. Forest Service in 2000, before beavers went to work.

    “When you see the results, it’s almost like magic,” Wilde says. Even more magical, the transformation cost Wilde only “a couple hundred bucks in fence posts” and a few days of sweat equity, thanks in part to those NRCS staffers who came in 2016 and a host of volunteers.

    Rock dams in the desert

    Beaver-powered restoration isn’t the answer everywhere, especially in the desert where creeks are ephemeral, flowing only intermittently. In Colorado’s Gunnison River basin, ranchers were looking for ways to boost water availability to ensure their cattle had enough drinking water and green grass in the face of climate change. Meanwhile, the area’s public land managers wanted to restore streams to help at-risk wildlife species like the Gunnison sage grouse, once prolific across sagebrush country.

    In 2012, a group of private landowners, public agencies and nonprofit organizations launched the Gunnison Basin Wet Meadow and Riparian Restoration and Resilience-building Project to revive streams and keep meadows green. The group hired Bill Zeedyk to instruct on how to build simple, low-profile dams by stacking rocks, known widely as Zeedyk structures, to slow down the water.

    Zeedyk, now 85, runs his own wetland and stream restoration firm in New Mexico, after 34 years as a wildlife biologist at the U.S. Forest Service. His 2014 book Let the Water Do the Work has inspired people across the West — including Maestas and Wheaton — to turn to simple, nature-based stream restoration solutions.

    Over the last nine years, Zeedyk has helped the Gunnison collaborative build nearly 2,000 rock structures throughout the roughly 10,000-square-kilometer upper Gunnison watershed. The group has restored 43 kilometers of stream and improved nearly 500 hectares of wet habitat for people and wildlife. A typical project involves a dozen volunteers working for a day or two in one creek bottom where they build dozens of rock structures.

    In 2017, Maestas asked Zeedyk to show more than 100 people involved in the NRCS-led Sage Grouse Initiative how to install rock structures. The white-bearded Zeedyk led them along an eroding gully near Gunnison that June.

    Conservation professionals gathered in Gunnison, Colo., in 2017 to learn how to build Zeedyk structures, simple rock dams that slow the flow of water in small creeks to increase surrounding plant growth.B. Randall

    Lifting his wooden walking staff, Zeedyk pointed out how the adjacent dirt road originally created by horses and wagons cut off the creek from its historic floodplain. The road made the channel shorter, straighter and steeper over time. “There’s less growing space, and the whole system is less productive,” he explained.

    As participants decided where to stack rocks to spread water across the dusty sagebrush flat, Zeedyk encouraged them to “read the landscape” and “think like water.” After three hours of work, participants could already see ponds forming behind their rock creations.

    Watching the teams work and laugh together, Maestas called it the aha moment for the crew. “When you get your hands dirty, there’s a degree of buy-in that can’t come from sitting in a classroom or reading about it.”

    The grass is greener

    The hope is that, like the beaver dam analogs, these hand-built rock structures will halt erosion, capture sediment, fill the floodplain sponge and grow more water-loving plants.

    Patience, Zeedyk says, is crucial. “After we put natural processes into play in a positive direction, we have to wait for the water to do its work.”

    The wait isn’t necessarily long. At four of the sites in the Gunnison basin restored with Zeedyk structures, wetland plant cover (including sedges, rushes, willows and wetland forbs) increased an average of 160 percent four years post-treatment, compared with a 15 percent average increase at untreated areas near each study site, according to a 2017 report by The Nature Conservancy.

    “As of 2019, we had increased the wetland species cover by 200 percent in six years,” says Renee Rondeau, an ecologist at the Colorado Natural Heritage Program, based in Hesperus. “So great to see this success.”

    Animals seem to enjoy all that fresh green growth too. Colorado Parks and Wildlife set up remote cameras to monitor whether wildlife use the restored floodplain. Since 2016, the cameras have captured more than 1.5 million images, most of which show a host of animals — from cattle and elk to sage grouse and voles — munching away in the now-lush meadows. A graduate student at Western Colorado University is classifying photos to determine whether there’s a significant difference in the number of Gunnison sage grouse at the restored sites compared with adjacent untreated areas.

    “Sage grouse chicks chase the green line as the desert dries up,” Maestas explains. After hatching in June, hens and their broods seek out wet areas where chicks stock up on protein-rich insects and wildflowers to grow and survive the winter.

    A remote camera spies Gunnison sage grouse feasting on insects and plants in a wet meadow. The area stays green long into the summer because of hand-built rock dams that spread water across the land.Courtesy of Nathan Seward/Colorado Parks and Wildlife

    Water in the bank

    The Gunnison basin is not the only place where sticks-and-stones restoration is paying dividends for people and wildlife. Nick Silverman, a hydroclimatologist and geospatial data scientist, and his colleagues at the University of Montana in Missoula used satellite imagery to evaluate changes in “greenness” at three sites that used different simple stream restoration treatments: Zeedyk’s rock structures in Gunnison, beaver dam analogs in Oregon’s Bridge Creek and fencing projects that kept livestock away from streambanks in northeastern Nevada’s Maggie Creek.

    Late summer greenness increased up to 25 percent after streams were restored compared with before, the researchers reported in 2018 in Restoration Ecology. Plus, the streams showed greater resilience to climate variability as time went on: Along Maggie Creek, restored more than two decades before the study, the plants stayed green even when rainfall was low, and the area had substantial increases in plant production during late summer, when vegetation usually dries out.

    “It’s like putting water in a piggy bank when it’s wet, so plants and animals can withdraw it later when it’s dry,” Silverman says. Even more exciting, he adds, is that the impact of the low-cost options is large enough to see from space.

    Water doesn’t burn

    The Sharps Fire that scorched south-central Idaho in July 2018 burned a wide swath of a watershed where Idaho Fish and Game had relocated beavers to restore a floodplain. A strip of wet, green vegetation stood untouched along the beavers’ ponds. Wheaton sent a drone to take photos, tweeting out an image on September 5, 2018: “Why is there an impressive patch of green in the middle of 65,000 acres of charcoal? Turns out water doesn’t burn. Thank you beaver!”

    The green strip of vegetation along beaver-made ponds in Baugh Creek near Hailey, Idaho, resisted flames when a wildfire scorched the region in 2018, as shown in this drone image.J. Wheaton/Utah State Univ.

    Fairfax, the ecohydrologist who reported that beaver dams increase streamside greenness, had been searching for evidence that beavers could help keep flames at bay. Wheaton’s tweet was a “kick in the pants to push my own research on beavers and fire forward,” she says.

    With undergraduate student Andrew Whittle, now at the Colorado School of Mines, Fairfax got to work analyzing satellite imagery from recent wildfires. The two mapped thousands of beaver dams within wildfire-burned areas in several western states. Choosing five fires of varying severity in both shrubland and forested areas, the pair analyzed the data to see if creeks with beaver activity stayed greener than creeks without beavers during wildfires.

    [embedded content]
    Emily Fairfax produced this stop-motion video to show how beavers and their dams and channels keep water in an area, supporting the surrounding vegetation and helping the area resist wildfires.

    “Across the board, beaver-dammed areas didn’t burn,” Fairfax says. The study was published last December in Ecological Applications during one of the West’s worst fire seasons. It garnered plenty of attention from land managers asking for more specifics, like how many beavers are needed to buffer a fire.

    Fairfax plans to study several more burned sites with beaver ponds. She hopes to eventually create a statistical model that can help people plan nature-powered stream restoration projects.

    “When we’re seeing hotter, more unpredictable fires that are breaking all the rules we know of,” Fairfax says, “we have to figure out how to preserve critical wet habitats.” More

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    in Computers Math

    After AIs mastered Go and Super Mario, scientists have taught them how to 'play' experiments

    Inspired by the mastery of artificial intelligence (AI) over games like Go and Super Mario, scientists at the National Synchrotron Light Source II (NSLS-II) trained an AI agent — an autonomous computational program that observes and acts — how to conduct research experiments at superhuman levels by using the same approach. The Brookhaven team published their findings in the journal Machine Learning: Science and Technology and implemented the AI agent as part of the research capabilities at NSLS-II.
    As a U.S. Department of Energy (DOE) Office of Science User Facility located at DOE’s Brookhaven National Laboratory, NSLS-II enables scientific studies by more than 2000 researchers each year, offering access to the facility’s ultrabright x-rays. Scientists from all over the world come to the facility to advance their research in areas such as batteries, microelectronics, and drug development. However, time at NSLS-II’s experimental stations — called beamlines — is hard to get because nearly three times as many researchers would like to use them as any one station can handle in a day — despite the facility’s 24/7 operations.
    “Since time at our facility is a precious resource, it is our responsibility to be good stewards of that; this means we need to find ways to use this resource more efficiently so that we can enable more science,” said Daniel Olds, beamline scientist at NSLS-II and corresponding author of the study. “One bottleneck is us, the humans who are measuring the samples. We come up with an initial strategy, but adjust it on the fly during the measurement to ensure everything is running smoothly. But we can’t watch the measurement all the time because we also need to eat, sleep and do more than just run the experiment.”
    “This is why we taught an AI agent to conduct scientific experiments as if they were video games. This allows a robot to run the experiment, while we — humans — are not there. It enables round-the-clock, fully remote, hands-off experimentation with roughly twice the efficiency that humans can achieve,” added Phillip Maffettone, research associate at NSLS-II and first author on the study.
    According to the researchers, they didn’t even have to give the AI agent the rules of the ‘game’ to run the experiment. Instead, the team used a method called “reinforcement learning” to train an AI agent on how to run a successful scientific experiment, and then tested their agent on simulated research data from the Pair Distribution Function beamline at NSLS-II.
    Beamline Experiments: A Boss Level Challenge
    Reinforcement learning is one strategy of training an AI agent to master an ability. The idea of reinforcement learning is that the AI agent perceives an environment — a world — and can influence it by performing actions. Depending on how the AI agent interacts with the world, it may receive a reward or a penalty, reflecting if this specific interaction is a good choice or a poor one. The trick is that the AI agent retains the memory of its interactions with the world, so that it can learn from the experience for when it tries again. In this way, the AI agent figures out how to master a task by collecting the most rewards. More

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    Soft robotic dragonfly signals environmental disruptions

    Engineers at Duke University have developed an electronics-free, entirely soft robot shaped like a dragonfly that can skim across water and react to environmental conditions such as pH, temperature or the presence of oil. The proof-of-principle demonstration could be the precursor to more advanced, autonomous, long-range environmental sentinels for monitoring a wide range of potential telltale signs of problems.
    The soft robot is described online March 25 in the journal Advanced Intelligent Systems.
    Soft robots are a growing trend in the industry due to their versatility. Soft parts can handle delicate objects such as biological tissues that metal or ceramic components would damage. Soft bodies can help robots float or squeeze into tight spaces where rigid frames would get stuck.
    The expanding field was on the mind of Shyni Varghese, professor of biomedical engineering, mechanical engineering and materials science, and orthopaedic surgery at Duke, when inspiration struck.
    “I got an email from Shyni from the airport saying she had an idea for a soft robot that uses a self-healing hydrogel that her group has invented in the past to react and move autonomously,” said Vardhman Kumar, a PhD student in Varghese’s laboratory and first author of the paper. “But that was the extent of the email, and I didn’t hear from her again for days. So the idea sort of sat in limbo for a little while until I had enough free time to pursue it, and Shyni said to go for it.”
    In 2012, Varghese and her laboratory created a self-healing hydrogel that reacts to changes in pH in a matter of seconds. Whether it be a crack in the hydrogel or two adjoining pieces “painted” with it, a change in acidity causes the hydrogel to form new bonds, which are completely reversible when the pH returns to its original levels. More

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    The very first structures in the Universe

    The very first moments of the Universe can be reconstructed mathematically even though they cannot be observed directly. Physicists from the Universities of Göttingen and Auckland (New Zealand) have greatly improved the ability of complex computer simulations to describe this early epoch. They discovered that a complex network of structures can form in the first trillionth of a second after the Big Bang. The behaviour of these objects mimics the distribution of galaxies in today’s Universe. In contrast to today, however, these primordial structures are microscopically small. Typical clumps have masses of only a few grams and fit into volumes much smaller than present-day elementary particles. The results of the study have been published in the journal Physical Review D.
    The researchers were able to observe the development of regions of higher density that are held together by their own gravity. “The physical space represented by our simulation would fit into a single proton a million times over,” says Professor Jens Niemeyer, head of the Astrophysical Cosmology Group at the University of Göttingen. “It is probably the largest simulation of the smallest area of the Universe that has been carried out so far.” These simulations make it possible to calculate more precise predictions for the properties of these vestiges from the very beginnings of the Universe.
    Although the computer-simulated structures would be very short-lived and eventually “vaporise” into standard elementary particles, traces of this extreme early phase may be detectable in future experiments. “The formation of such structures, as well as their movements and interactions, must have generated a background noise of gravitational waves,” says Benedikt Eggemeier, a PhD student in Niemeyer’s group and first author of the study. “With the help of our simulations, we can calculate the strength of this gravitational wave signal, which might be measurable in the future.”
    It is also conceivable that tiny black holes could form if these structures undergo runaway collapse. If this happens they could have observable consequences today, or form part of the mysterious dark matter in the Universe. “On the other hand,” says Professor Easther, “If the simulations predict black holes form, and we don’t see them, then we will have found a new way to test models of the infant Universe.”
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    in Computers Math

    How tiny machines become capable of learning

    Microswimmers are artificial, self-propelled, microscopic particles. They are capable of directional motion in a solution. The Molecular Nanophotonics Group at Leipzig University has developed special particles that are smaller than one-thirtieth of the diameter of a hair. They can change their direction of motion by heating tiny gold particles on their surface and converting this energy into motion. “However, these miniaturised machines cannot take in and learn information like their living counterparts. To achieve this, we control the microswimmers externally so that they learn to navigate in a virtual environment through what is known as reinforcement learning,” said Cichos.
    With the help of virtual rewards, the microswimmers find their way through the liquid while repeatedly being thrown off of their path, mainly by Brownian motion. “Our results show that the best swimmer is not the one that is fastest, but rather that there is an optimal speed,” said Viktor Holubec, who worked on the project as a fellow of the Alexander von Humboldt Foundation and has now returned to the university in Prague.
    According to the scientists, linking artificial intelligence and active systems like in these microswimmers is a first small step towards new intelligent microscopic materials that can autonomously perform tasks while also adapting to their new environment. At the same time, they hope that the combination of artificial microswimmers and machine learning methods will provide new insights into the emergence of collective behaviour in biological systems. “Our goal is to develop artificial, smart building blocks that can perceive their environmental influences and actively react to them,” said the physicist. Once this method is fully developed and has been applied to other material systems, including biological ones, it could be used, for example, in the development of smart drugs or microscopic robot swarms.
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    Optical fiber could boost power of superconducting quantum computers

    The secret to building superconducting quantum computers with massive processing power may be an ordinary telecommunications technology — optical fiber.
    Physicists at the National Institute of Standards and Technology (NIST) have measured and controlled a superconducting quantum bit (qubit) using light-conducting fiber instead of metal electrical wires, paving the way to packing a million qubits into a quantum computer rather than just a few thousand. The demonstration is described in the March 25 issue of Nature.
    Superconducting circuits are a leading technology for making quantum computers because they are reliable and easily mass produced. But these circuits must operate at cryogenic temperatures, and schemes for wiring them to room-temperature electronics are complex and prone to overheating the qubits. A universal quantum computer, capable of solving any type of problem, is expected to need about 1 million qubits. Conventional cryostats — supercold dilution refrigerators — with metal wiring can only support thousands at the most.
    Optical fiber, the backbone of telecommunications networks, has a glass or plastic core that can carry a high volume of light signals without conducting heat. But superconducting quantum computers use microwave pulses to store and process information. So the light needs to be converted precisely to microwaves.
    To solve this problem, NIST researchers combined the fiber with a few other standard components that convert, convey and measure light at the level of single particles, or photons, which could then be easily converted into microwaves. The system worked as well as metal wiring and maintained the qubit’s fragile quantum states.
    “I think this advance will have high impact because it combines two totally different technologies, photonics and superconducting qubits, to solve a very important problem,” NIST physicist John Teufel said. “Optical fiber can also carry far more data in a much smaller volume than conventional cable.”
    Normally, researchers generate microwave pulses at room temperature and then deliver them through coaxial metal cables to ¬¬cryogenically maintained superconducting qubits. The new NIST setup used an optical fiber instead of metal to guide light signals to cryogenic photodetectors that converted signals back to microwaves and delivered them to the qubit. For experimental comparison purposes, microwaves could be routed to the qubit through either the photonic link or a regular coaxial line. More

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    Semiconductor qubits scale in two dimensions

    The heart of any computer, its central processing unit, is built using semiconductor technology, which is capable of putting billions of transistors onto a single chip. Now, researchers from the group of Menno Veldhorst at QuTech, a collaboration between TU Delft and TNO, have shown that this technology can be used to build a two-dimensional array of qubits to function as a quantum processor. Their work, a crucial milestone for scalable quantum technology, was published today in Nature.
    Quantum computers have the potential to solve problems that are impossible to address with classical computers. Whereas current quantum devices hold tens of qubits — the basic building block of quantum technology — a future universal quantum computer capable of running any quantum algorithm will likely consist of millions to billions of qubits. Quantum dot qubits hold the promise to be a scalable approach as they can be defined using standard semiconductor manufacturing techniques. Veldhorst: ‘By putting four such qubits in a two-by-two grid, demonstrating universal control over all qubits, and operating a quantum circuit that entangles all qubits, we have made an important step forward in realizing a scalable approach for quantum computation.’
    An entire quantum processor
    Electrons trapped in quantum dots, semiconductor structures of only a few tens of nanometres in size, have been studied for more than two decades as a platform for quantum information. Despite all promises, scaling beyond two-qubit logic has remained elusive. To break this barrier, the groups of Menno Veldhorst and Giordano Scappucci decided to take an entirely different approach and started to work with holes (i.e. missing electrons) in germanium. Using this approach, the same electrodes needed to define the qubits could also be used to control and entangle them. ‘No large additional structures have to be added next to each qubit such that our qubits are almost identical to the transistors in a computer chip,’ says Nico Hendrickx, graduate student in the group of Menno Veldhorst and first author of the article. ‘Furthermore, we have obtained excellent control and can couple qubits at will, allowing us to program one, two, three, and four-qubit gates, promising highly compact quantum circuits.’
    2D is key
    After successfully creating the first germanium quantum dot qubit in 2019, the number of qubits on their chips has doubled every year. ‘Four qubits by no means makes a universal quantum computer, of course,’ Veldhorst says. ‘But by putting the qubits in a two-by-two grid we now know how to control and couple qubits along different directions.’ Any realistic architecture for integrating large numbers of qubits requires them to be interconnected along two dimensions.
    Germanium as a highly versatile platform
    Demonstrating four-qubit logic in germanium defines the state-of-the-art for the field of quantum dots and marks an important step toward dense, and extended, two-dimensional semiconductor qubit grids. Next to its compatibility with advanced semiconductor manufacturing, germanium is also a highly versatile material. It has exciting physics properties such as spin-orbit coupling and it can make contact to materials like superconductors. Germanium is therefore considered as an excellent platform in several quantum technologies. Veldhorst: ‘Now that we know how to manufacture germanium and operate an array of qubits, the germanium quantum information route can truly begin.’
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    Wafer-thin nanopaper changes from firm to soft at the touch of a button

    Materials science likes to take nature and the special properties of living beings that could potentially be transferred to materials as a model. A research team led by chemist Professor Andreas Walther of Johannes Gutenberg University Mainz (JGU) has succeeded in endowing materials with a bioinspired property: Wafer-thin stiff nanopaper instantly becomes soft and elastic at the push of a button. “We have equipped the material with a mechanism so that the strength and stiffness can be modulated via an electrical switch,” explained Walther. As soon as an electric current is applied, the nanopaper becomes soft; when the current flow stops, it regains its strength. From an application perspective, this switchability could be interesting for damping materials, for example. The work, which also involved scientists from the University of Freiburg and the Cluster of Excellence on “Living, Adaptive, and Energy-autonomous Materials Systems” (livMatS) funded by the German Research Foundation (DFG), was published in Nature Communications.
    Inspiration from the seafloor: Mechanical switch serves a protective function
    The nature-based inspiration in this case comes from sea cucumbers. These marine creatures have a special defense mechanism: When they are attacked by predators in their habitat on the seafloor, sea cucumbers can adapt and strengthen their tissue so that their soft exterior immediately stiffens. “This is an adaptive mechanical behavior that is fundamentally difficult to replicate,” said Professor Andreas Walther. With their work now published, his team has succeeded in mimicking the basic principle in a modified form using an attractive material and an equally attractive switching mechanism.
    The scientists used cellulose nanofibrils extracted and processed from the cell wall of trees. Nanofibrils are even finer than the microfibers in standard paper and result in a completely transparent, almost glass-like paper. The material is stiff and strong, appealing for lightweight construction. Its characteristics are even comparable to those of aluminum alloys. In their work, the research team applied electricity to these cellulose nanofibril-based nanopapers. By means of specially designed molecular changes, the material becomes flexible as a result. The process is reversible and can be controlled by an on/off switch.
    “This is extraordinary. All the materials around us are not very changeable, they do not easily switch from stiff to elastic and vice versa. Here, with the help of electricity, we can do that in a simple and elegant way,” said Walther. The development is thus moving away from classic static materials toward materials with properties that can be adaptively adjusted. This is relevant for mechanical materials, which can thus be made more resistant to fracture, or for adaptive damping materials, which could switch from stiff to compliant when overloaded, for example.
    Targeting a material with its own energy storage for autonomous on/off switching
    At the molecular level, the process involves heating the material by applying a current and thus reversibly breaking cross-linking points. The material softens in correlation with the applied voltage, i.e., the higher the voltage, the more cross-linking points are broken and the softer the material becomes. Professor Andreas Walther’s vision for the future also starts at the point of power supply: While currently a power source is needed to start the reaction, the next goal would be to produce a material with its own energy storage system, so that the reaction is essentially triggered “internally” as soon as, for example, an overload occurs and damping becomes necessary. “Now we still have to flip the switch ourselves, but our dream would be for the material system to be able to accomplish this on its own.”
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