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      ‘Designer molecules’ could create tailor-made quantum devices

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      Quantum bits made from “designer molecules” are coming into fashion. By carefully tailoring the composition of molecules, researchers are creating chemical systems suited to a variety of quantum tasks.
      “The ability to control molecules … makes them just a beautiful and wonderful system to work with,” said Danna Freedman, a chemist at Northwestern University in Evanston, Ill. “Molecules are the best.” Freedman described her research February 8 at the annual meeting of the American Association for the Advancement of Science, held online.
      Quantum bits, or qubits, are analogous to the bits found in conventional computers. But rather than existing in a state of either 0 or 1, as standard bits do, qubits can possess both values simultaneously, enabling new types of calculations impossible for conventional computers.
      Besides their potential use in quantum computers, molecules can also serve as quantum sensors, devices that can make extremely sensitive measurements, such as sussing out minuscule electromagnetic forces (SN: 3/23/18).

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      In Freedman and colleagues’ qubits, a single chromium ion, an electrically charged atom, sits at the center of the molecule. The qubit’s value is represented by that chromium ion’s electronic spin, a measure of the angular momentum of its electrons. Additional groups of atoms are attached to the chromium; by swapping out some of the atoms in those groups, the researchers can change the qubit’s properties to alter how it functions.
      Recently, Freedman and colleagues crafted molecules to fit one particular need: molecular qubits that respond to light. Lasers can set the values of the qubits and help read out the results of calculations, the researchers reported in the Dec. 11 Science. Another possibility might be to create molecules that are biocompatible, Freedman says, so they can be used for sensing conditions inside living tissue.
      Molecules have another special appeal: All of a given type are exactly the same. Many types of qubits are made from bits of metal or other material deposited on a surface, resulting in slight differences between qubits on an atomic level. But using chemical techniques to build up molecules atom by atom means the qubits are identical, making for better-performing devices. “That’s something really powerful about the bottom-up approach that chemistry affords,” said Freedman.
      Scientists are already using individual atoms and ions in quantum devices (SN: 6/29/17), but molecules are more complicated to work with, thanks to their multiple constituents. As a result, molecules are a relatively new quantum resource, Caltech physicist Nick Hutzler said at the meeting. “People don’t even really know what you can do with [molecules] yet.… But people are discovering new things every day.” More

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      How one physicist is unraveling the mathematics of knitting

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      Physicist Elisabetta Matsumoto is an avid knitter and has been since taking up the hobby as a child. During graduate school at the University of Pennsylvania in 2009, Matsumoto came across an unusually knotty stitch while knitting a pattern for a Japanese red dragon. “I have books with thousands of different stitch patterns, but the one in the red dragon wall hanging was one I had never seen,” she says. That got her thinking about the geometry of stitches and, eventually, led her to study the mathematics of knitting.
      There are a hundred or so basic stitches, Matsumoto says. By varying stitch combinations, a knitter can alter the elasticity, mechanical strength and 3-D structure of the resulting fabric. Yarn on its own isn’t very elastic. But when knitted, the yarn gives rise to fabric that can stretch by more than twice its length while the yarn itself barely stretches.
      Matsumoto, now at the Georgia Institute of Technology in Atlanta, is teasing out the mathematical rules that dictate how stitches impart such unique properties to fabrics. She hopes to develop a catalog of stitch types, their combinations and the resulting fabric properties. Knitters, scientists and manufacturers could all benefit from a dictionary of knits, she says.
      Elisabetta Matsumoto, a physicist at the Georgia Institute of Technology in Atlanta, hopes to create a dictionary of knits that could be used to manipulate physical properties of materials.Courtesy of Elisabetta Matsumoto
      Matsumoto’s research builds on knot theory (SN: 10/31/08), a set of mathematical principles that define how knots form. These principles have helped explain how DNA folds and unfolds and how a molecule’s makeup and distribution in space impart it with physical and chemical characteristics (SN: 5/23/08; SN: 8/27/18). Matsumoto is using knot theory to understand how each stitch entangles with its neighbors. “The types of stitches, the differences in their geometries as well as the order in which you put those stitches together into a textile may determine [the fabric’s] properties,” she says.
      Making tiny changes, such as altering a couple of crossings in a knot, could have a huge impact on the mechanics of the textile. For instance, a fabric made of just one stitch type, such as a knit or purl, tends to curl at the edges. But combine the two stitch types together in alternating rows or columns, and the fabric lays flat. And despite looking nearly identical, the fabrics have varying degrees of stretchiness, Matsumoto and grad student Shashank Markande reported in July in the Bridges 2020 Conference Proceedings.
      Matsumoto’s team is now training a computer to think like a knitter. Using yarn properties, mathematical stitch details and final knitted structures as inputs, a program can predict mechanical properties of fabrics. These predictions could someday help tailor materials for specific applications — from scaffolds for growing human tissue to wearable smart clothing (SN: 6/1/18) — and perhaps solve knotty problems of everyday life. More

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      A robot arm toting a Venus flytrap can grab delicate objects

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      A new robotic grabber is ripped straight from the plant world. The device, made with a severed piece of a Venus flytrap, can grasp tiny, delicate objects, researchers report January 25 in Nature Electronics.
      Normally, the carnivorous Dionaea muscipula scores a meal when unsuspecting prey touches delicate hairs on one of the plant’s jawlike leaves, triggering the trap to snap shut (SN: 10/14/20). But by sticking electrodes to the leaves and applying a small electric voltage, researchers designed a method to force Venus flytraps to close. Even when cut from the plant, the leaves retained the ability to shut upon command for up to a day, say materials scientist Wenlong Li and colleagues at Nanyang Technological University in Singapore.
      Integrating soft, flexible plant material into robotics could aid in picking up fragile objects that would otherwise be damaged by clunky, rigid graspers, the researchers say. So, Li’s team attached a piece of a flytrap to a robotic arm and used a smartphone app to control the trap. In experiments, the robotic grabber clutched a piece of wire one-half of a millimeter in diameter. And when not strapped to the robotic arm, the dismembered plant also caught a slowly moving 1-gram weight.
      One drawback: The traps take hours to reopen, meaning this bot had better make the catch on the first try.
      [embedded content]
      Scientists controlled a Venus flytrap outfitted with electrodes, using a smartphone to direct it to grasp small objects like a wire and a moving weight. More

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      Drones could help create a quantum internet

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      The quantum internet may be coming to you via drone.
      Scientists have now used drones to transmit particles of light, or photons, that share the quantum linkage called entanglement. The photons were sent to two locations a kilometer apart, researchers from Nanjing University in China report in a study to appear in Physical Review Letters.
      Entangled quantum particles can retain their interconnected properties even when separated by long distances. Such counterintuitive behavior can be harnessed to allow new types of communication. Eventually, scientists aim to build a global quantum internet that relies on transmitting quantum particles to enable ultrasecure communications by using the particles to create secret codes to encrypt messages. A quantum internet could also allow distant quantum computers to work together, or perform experiments that test the limits of quantum physics.
      Quantum networks made with fiber-optic cables are already beginning to be used (SN: 9/28/20). And a quantum satellite can transmit photons across China (SN: 6/15/17). Drones could serve as another technology for such networks, with the advantages of being easily movable as well as relatively quick and cheap to deploy.
      The researchers used two drones to transmit the photons. One drone created pairs of entangled particles, sending one particle to a station on the ground while relaying the other to the second drone. That machine then transmitted the particle it received to a second ground station a kilometer away from the first. In the future, fleets of drones could work together to send entangled particles to recipients in a variety of locations. More

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      Galileo’s famous gravity experiment holds up, even with individual atoms

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      According to legend, Galileo dropped weights off of the Leaning Tower of Pisa, showing that gravity causes objects of different masses to fall with the same acceleration. In recent years, researchers have taken to replicating this test in a way that the Italian scientist probably never envisioned — by dropping atoms.
      A new study describes the most sensitive atom-drop test so far and shows that Galileo’s gravity experiment still holds up — even for individual atoms. Two different types of atoms had the same acceleration within about a part per trillion, or 0.0000000001 percent, physicists report in a paper in press in Physical Review Letters.
      Compared with a previous atom-drop test, the new research is a thousand times as sensitive. “It represents a leap forward,” says physicist Guglielmo Tino of the University of Florence, who was not involved with the new study.
      Researchers compared rubidium atoms of two different isotopes, atoms that contain different numbers of neutrons in their nuclei. The team launched clouds of these atoms about 8.6 meters high in a tube under vacuum. As the atoms rose and fell, both varieties accelerated at essentially the same rate, the researchers found.

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      In confirming Galileo’s gravity experiment yet again, the result upholds the equivalence principle, a foundation of Albert Einstein’s theory of gravity, general relativity. That principle states that an object’s inertial mass, which determines how much it accelerates when force is applied, is equivalent to its gravitational mass, which determines how strong a gravitational force it feels. The upshot: An object’s acceleration under gravity doesn’t depend on its mass or composition.
      So far, the equivalence principle has withstood all tests. But atoms, which are subject to the strange laws of quantum mechanics, could reveal its weak points. “When you do the test with atoms … you’re testing the equivalence principle and stressing it in new ways,” says physicist Mark Kasevich of Stanford University.
      Kasevich and colleagues studied the tiny particles using atom interferometry, which takes advantage of quantum mechanics to make extremely precise measurements. During the atoms’ flight, the scientists put the atoms in a state called a quantum superposition, in which particles don’t have one definite location. Instead, each atom existed in a superposition of two locations, separated by up to seven centimeters. When the atoms’ two locations were brought back together, the atoms interfered with themselves in a way that precisely revealed their relative acceleration.
      Many scientists think that the equivalence principle will eventually falter. “We have reasonable expectations that our current theories … are not the end of the story,” says physicist Magdalena Zych of the University of Queensland in Brisbane, Australia, who was not involved with the research. That’s because quantum mechanics — the branch of physics that describes the counterintuitive physics of the very small — doesn’t mesh well with general relativity, leading scientists on a hunt for a theory of quantum gravity that could unite these ideas. Many scientists suspect that the new theory will violate the equivalence principle by an amount too small to have been detected with tests performed thus far.
      But physicists hope to improve such atom-based tests in the future, for example by performing them in space, where objects can free-fall for extended periods of time. An equivalence principle test in space has already been performed with metal cylinders, but not yet with atoms (SN: 12/4/17).
      So there’s still a chance to prove Galileo wrong. More

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      The diabolical ironclad beetle can survive getting run over by a car. Here’s how

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      The diabolical ironclad beetle is like a tiny tank on six legs.
      This insect’s rugged exoskeleton is so tough that the beetle can survive getting run over by cars, and many would-be predators don’t stand a chance of cracking one open. Phloeodes diabolicus is basically nature’s jawbreaker.
      Analyses of microscope images, 3-D printed models and computer simulations of the beetle’s armor have now revealed the secrets to its strength. Tightly interlocked and impact-absorbing structures that connect pieces of the beetle’s exoskeleton help it survive enormous crushing forces, researchers report in the Oct. 22 Nature. Those features could inspire new, sturdier designs for things such as body armor, buildings, bridges and vehicles.
      The diabolical ironclad beetle, which dwells in desert regions of western North America, has a distinctly hard-to-squish shape. “Unlike a stink beetle, or a Namibian beetle, which is more rounded … it’s low to the ground [and] it’s flat on top,” says David Kisailus, a materials scientist at the University of California, Irvine. In compression experiments, Kisailus and colleagues found that the beetle could withstand around 39,000 times its own body weight. That would be like a person shouldering a stack of about 40 M1 Abrams battle tanks.
      Within the diabolical ironclad beetle’s own tanklike physique, two key microscopic features help it withstand crushing forces. The first is a series of connections between the top and bottom halves of the exoskeleton. “You can imagine the beetle’s exoskeleton almost like two halves of a clamshell sitting on top of each other,” Kisailus says. Ridges along the outer edges of the top and bottom latch together.
      This slice of a diabolical ironclad beetle’s back shows the jigsaw-shaped links that connect the left and right sides of its exoskeleton. These protrusions are tightly interlocked and highly damage-resistant, helping give the beetle its incredible durability.David Kisailus
      But those ridged connections have different shapes across the beetle’s body. Near the front of the beetle, around its vital organs, the ridges are highly interconnected — almost like zipper teeth. Those connections are stiff and resist bending under pressure.
      The connective ridges near the back of the beetle, on the other hand, are not as intricately interlocked, allowing the top and bottom halves of the exoskeleton to slide past each other slightly. That flexibility helps the beetle absorb compression in a region of its body that is safer to squish.
      The second key feature is a rigid joint, or suture, that runs the length of the beetle’s back and connects its left and right sides. A series of protrusions, called blades, fit together like jigsaw puzzle pieces to join the two sides. These blades contain layers of tissue glued together by proteins, and are highly damage-resistant. When the beetle is squashed, tiny cracks form in the protein glue between the layers of each blade. Those small, healable fractures allow the blades to absorb impacts without completely snapping, explains Jesus Rivera, an engineer at UC Irvine.

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      This toughness makes the diabolical ironclad beetle pretty predator-proof. An animal might be able to make a meal out of the beetle by swallowing it whole, Kisailus says. “But the way it’s built, in terms of other predation — let’s say like a bird that’s pecking at it, or a lizard that’s trying to chew on it — the exoskeleton would be really hard” to crack.
      That hard exterior is also a nuisance for insect collectors. The diabolical ironclad beetle is notorious among entomologists for being so fantastically durable that it bends the steel pins usually used to mount insects for display, says entomologist Michael Caterino of Clemson University in South Carolina. But “the basic biology of this thing is not particularly well-known,” he says. “I found it fascinating” to learn what makes the beetle so indestructible.
      The possibility of using beetle-inspired designs for sturdier airplanes and other structures is intriguing, Caterino adds. And with the splendid variety of insects all over the world, who knows what other critters might someday inspire clever engineering designs. More

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      The first room-temperature superconductor has finally been found

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      It’s here: Scientists have reported the discovery of the first room-temperature superconductor, after more than a century of waiting.
      The discovery evokes daydreams of futuristic technologies that could reshape electronics and transportation. Superconductors transmit electricity without resistance, allowing current to flow without any energy loss. But all superconductors previously discovered must be cooled, many of them to very low temperatures, making them impractical for most uses.
      Now, scientists have found the first superconductor that operates at room temperature — at least given a fairly chilly room. The material is superconducting below temperatures of about 15° Celsius (59° Fahrenheit), physicist Ranga Dias of the University of Rochester in New York and colleagues report October 14 in Nature.
      The team’s results “are nothing short of beautiful,” says materials chemist Russell Hemley of the University of Illinois at Chicago, who was not involved with the research.
      However, the new material’s superconducting superpowers appear only at extremely high pressures, limiting its practical usefulness.

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      Dias and colleagues formed the superconductor by squeezing carbon, hydrogen and sulfur between the tips of two diamonds and hitting the material with laser light to induce chemical reactions. At a pressure about 2.6 million times that of Earth’s atmosphere, and temperatures below about 15° C, the electrical resistance vanished.
      That alone wasn’t enough to convince Dias. “I didn’t believe it the first time,” he says. So the team studied additional samples of the material and investigated its magnetic properties.
      Superconductors and magnetic fields are known to clash — strong magnetic fields inhibit superconductivity. Sure enough, when the material was placed in a magnetic field, lower temperatures were needed to make it superconducting. The team also applied an oscillating magnetic field to the material, and showed that, when the material became a superconductor, it expelled that magnetic field from its interior, another sign of superconductivity.
      The scientists were not able to determine the exact composition of the material or how its atoms are arranged, making it difficult to explain how it can be superconducting at such relatively high temperatures. Future work will focus on describing the material more completely, Dias says.
      When superconductivity was discovered in 1911, it was found only at temperatures close to absolute zero (−273.15° C). But since then, researchers have steadily uncovered materials that superconduct at higher temperatures. In recent years, scientists have accelerated that progress by focusing on hydrogen-rich materials at high pressure.
      In 2015, physicist Mikhail Eremets of the Max Planck Institute for Chemistry in Mainz, Germany, and colleagues squeezed hydrogen and sulfur to create a superconductor at temperatures up to −70° C (SN: 12/15/15). A few years later, two groups, one led by Eremets and another involving Hemley and physicist Maddury Somayazulu, studied a high-pressure compound of lanthanum and hydrogen. The two teams found evidence of superconductivity at even higher temperatures of −23° C and −13° C, respectively, and in some samples possibly as high as 7° C (SN: 9/10/18).
      The discovery of a room-temperature superconductor isn’t a surprise. “We’ve been obviously heading toward this,” says theoretical chemist Eva Zurek of the University at Buffalo in New York, who was not involved with the research. But breaking the symbolic room-temperature barrier is “a really big deal.”
      If a room-temperature superconductor could be used at atmospheric pressure, it could save vast amounts of energy lost to resistance in the electrical grid. And it could improve current technologies, from MRI machines to quantum computers to magnetically levitated trains. Dias envisions that humanity could become a “superconducting society.”
      But so far scientists have created only tiny specks of the material at high pressure, so practical applications are still a long way off.
      Still, “the temperature is not a limit anymore,” says Somayazulu, of Argonne National Laboratory in Lemont, Ill., who was not involved with the new research. Instead, physicists now have a new aim: to create a room-temperature superconductor that works without putting on the squeeze, Somayazulu says. “That’s the next big step we have to do.”

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