Computers Math

Artificial intelligence (AI) may offer a way to accurately determine that a person is not infected with COVID-19. An international retrospective study finds that infection with SARS-CoV-2, the virus that causes COVID-19, creates subtle electrical changes in the heart. An AI-enhanced EKG can detect these changes and potentially be used as a rapid, reliable COVID-19 screening test to rule out COVID-19 infection.
The AI-enhanced EKG was able to detect COVID-19 infection in the test with a positive predictive value — people infected — of 37% and a negative predictive value — people not infected — of 91%. When additional normal control subjects were added to reflect a 5% prevalence of COVID-19 — similar to a real-world population — the negative predictive value jumped to 99.2%. The findings are published in Mayo Clinic Proceedings.
COVID-19 has a 10- to 14-day incubation period, which is long compared to other common viruses. Many people do not show symptoms of infection, and they could unknowingly put others at risk. Also, the turnaround time and clinical resources needed for current testing methods are substantial, and access can be a problem.
“If validated prospectively using smartphone electrodes, this will make it even simpler to diagnose COVID infection, highlighting what might be done with international collaborations,” says Paul Friedman, M.D., chair of Mayo Clinic’s Department of Cardiovascular Medicine in Rochester. Dr. Friedman is senior author of the study.
The realization of a global health crisis brought together stakeholders around the world to develop a tool that could address the need to rapidly, noninvasively and cost-effectively rule out the presence of acute COVID-19 infection. The study, which included data from racially diverse populations, was conducted through a global volunteer consortium spanning four continents and 14 countries.
“The lessons from this global working group showed what is feasible, and the need pushed members in industry and academia to partner in solving the complex questions of how to gather and transfer data from multiple centers with their own EKG systems, electronic health records and variable access to their own data,” says Suraj Kapa, M.D., a cardiac electrophysiologist at Mayo Clinic. “The relationships and data processing frameworks refined through this collaboration can support the development and validation of new algorithms in the future.”
The researchers selected patients with EKG data from around the time their COVID-19 diagnosis was confirmed by a genetic test for the SARS-Co-V-2 virus. These data were control-matched with similar EKG data from patients who were not infected with COVID-19. More

Researchers have discovered a new and more efficient computing method for pairing the reliability of a classical computer with the strength of a quantum system.
This new computing method opens the door to different algorithms and experiments that bring quantum researchers closer to near-term applications and discoveries of the technology.
“In the future, quantum computers could be used in a wide variety of applications including helping to remove carbon dioxide from the atmosphere, developing artificial limbs and designing more efficient pharmaceuticals,” said Christine Muschik, a principal investigator at the Institute for Quantum Computing (IQC) and a faculty member in physics and astronomy at the University of Waterloo.
The research team from IQC in partnership with the University of Innsbruck is the first to propose the measurement-based approach in a feedback loop with a regular computer, inventing a new way to tackle hard computing problems. Their method is resource-efficient and therefore can use small quantum states because they are custom-tailored to specific types of problems.
Hybrid computing, where a regular computer’s processor and a quantum co-processor are paired into a feedback loop, gives researchers a more robust and flexible approach than trying to use a quantum computer alone.
While researchers are currently building hybrid, computers based on quantum gates, Muschik’s research team was interested in the quantum computations that could be done without gates. They designed an algorithm in which a hybrid quantum-classical computation is carried out by performing a sequence of measurements on an entangled quantum state.
The team’s theoretical research is good news for quantum software developers and experimentalists because it provides a new way of thinking about optimization algorithms. The algorithm offers high error tolerance, often an issue in quantum systems, and works for a wide range of quantum systems, including photonic quantum co-processors.
Hybrid computing is a novel frontier in near-term quantum applications. By removing the reliance on quantum gates, Muschik and her team have removed the struggle with finicky and delicate resources and instead, by using entangled quantum states, they believe they will be able to design feedback loops that can be tailored to the datasets that the computers are researching in a more efficient manner.
“Quantum computers have the potential to solve problems that supercomputers can’t, but they are still experimental and fragile,” said Muschik.
This project is funded by CIFAR.
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Materials provided by University of Waterloo. Note: Content may be edited for style and length. More

Researchers from The Australian National University (ANU) have developed new technology that allows people to see clearly in the dark, revolutionising night-vision.
The first-of-its-kind thin film, described in a new article published in Advanced Photonics, is ultra-compact and one day could work on standard glasses.
The researchers say the new prototype tech, based on nanoscale crystals, could be used for defence, as well as making it safer to drive at night and walking home after dark.
The team also say the work of police and security guards — who regularly employ night vision — will be easier and safer, reducing chronic neck injuries from currently bulk night-vision devices.
“We have made the invisible visible,” lead researcher Dr Rocio Camacho Morales said.
“Our technology is able to transform infrared light, normally invisible to the human eye, and turn this into images people can clearly see — even at distance. More

Research led by the University of Kent and the STFC Rutherford Appleton Laboratory has resulted in the discovery of a new rare topological superconductor, LaPt3P. This discovery may be of huge importance to the future operations of quantum computers.
Superconductors are vital materials able to conduct electricity without any resistance when cooled below a certain temperature, making them highly desirable in a society needing to reduce its energy consumption.
Superconductors manifest quantum properties on the scale of everyday objects, making them highly attractive candidates for building computers which use quantum physics to store data and perform computing operations, and can vastly outperform even the best supercomputers in certain tasks. As a result, there is an increasing demand from leading tech companies like Google, IBM and Microsoft to make quantum computers on an industrial scale using superconductors.
However, the elementary units of quantum computers (qubits) are extremely sensitive and lose their quantum properties due to electromagnetic fields, heat and collisions with air molecules. Protection from these can be achieved by making more resilient qubits using a special class of superconductors called topological superconductors which in addition to being superconductors also host protected metallic states on their boundaries or surfaces.
Topological superconductors, such as LaPt3P, newly discovered through muon spin relaxation experiments and extensive theoretical analysis, are exceptionally rare and are of tremendous value to the future industry of quantum computing.
To ensure its properties are sample and instrument independent, two different sets of samples were prepared in the University of Warwick and in ETH Zurich. Muon experiments were then performed in two different types of muon facilities: in the ISIS Pulsed Neutron and Muon Source in the STFC Rutherford Appleton Laboratory and in PSI, Switzerland.
Dr Sudeep Kumar Ghosh, Leverhulme Early Career Fellow at Kent and Principle Investigator said: ‘This discovery of the topological superconductor LaPt3P has tremendous potential in the field of quantum computing. Discovery of such a rare and desired component demonstrates the importance of muon research for the everyday world around us.’
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Materials provided by University of Kent. Original written by Sam Wood. Note: Content may be edited for style and length. More

A new model that applies artificial intelligence to carbohydrates improves the understanding of the infection process and could help predict which viruses are likely to spread from animals to humans. This is reported in a recent study led by researchers at the University of Gothenburg.
Carbohydrates participate in nearly all biological processes — yet they are still not well understood. Referred to as glycans, these carbohydrates are crucial to making our body work the way it is supposed to. However, with a frightening frequency, they are also involved when our body does not work as intended. Nearly all viruses use glycans as their first contact with our cells in the process of infection, including our current menace SARS-CoV-2, causing the COVID-19 pandemic.
A research group led by Daniel Bojar, assistant professor at the University of Gothenburg, has now developed an artificial intelligence-based model to analyze glycans with an unprecedented level of accuracy. The model improves the understanding of the infection process by making it possible to predict new virus-glycan interactions, for example between glycans and influenza viruses or rotaviruses: a common cause for viral infections in infants.
As a result, the model can also lead to a better understanding of zoonotic diseases, where viruses spread from animals to humans.
“With the emergence of SARS-CoV-2, we have seen the potentially devastating consequences of viruses jumping from animals to humans. Our model can now be used to predict which viruses are particularly close to “jumping over.” We can analyze this by seeing how many mutations would be necessary for the viruses to recognize human glycans, which increases the risk of human infection. Also, the model helps us predict which parts of the human body are likely targeted by a potentially zoonotic virus, such as the respiratory system or the gastrointestinal tract,” says Daniel Bojar, who is the main author of the study.
In addition, the research group hopes to leverage the improved understanding of the infection process to prevent viral infection. The aim is to use the model to develop glycan-based antivirals, medicines that suppress the ability of viruses to replicate.
“Predicting virus-glycan interactions means we can now search for glycans that bind viruses better than our own glycans do, and use these “decoy” glycans as antivirals to prevent viral infection. However, further advances in glycan manufacturing are necessary, as potential antiviral glycans might include diverse sequences that are currently difficult to produce,” Daniel Bojar says.
He hopes the model will constitute a step towards including glycans in approaches to prevent and combat future pandemics, as they are currently neglected in favor of molecules that are simpler to analyze, such as DNA.
“The work of many groups in recent years has really revolutionized glycobiology and I think we are finally at the cusp of using these complex biomolecules for medical purposes. Exciting times are ahead,” says Daniel Bojar.
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Materials provided by University of Gothenburg. Original written by Ulrika Ernström. Note: Content may be edited for style and length. More

Near-field light is invisible light at the subwavelength scale. Harnessed for a variety of practical applications, such as wireless power transfer, near-field light has an increasingly significant role in the development of miniature on-chip photonic devices. Controlling the direction of near-field light propagation has been an ongoing challenge that is of fundamental interest in photonics physics and can significantly advance a variety of applications.
So far, propagation of near-field light in a single direction is achieved by specific interactions between the electric dipole and the magnetic dipole in a system, which has led to inevitable complexities in device design. Hyperbolic metamaterials (HMMs), an important class of artificial anisotropic material with hyperbolic isofrequency contours, have attracted attention due to their unique ability to control near-field light by enabling subwavelength confinement of electromagnetic waves. Large wave-vector modes in HMMs are of particular interest because those modes are easier to integrate and have a smaller loss of energy at transfer.
As reported in Advanced Photonics, researchers from Tongji University in China recently demonstrated an all-electric scheme able to flexibly control the propagation direction of near-field light. They reported anomalous unidirectional excitation of hyperbolic modes with large wave-vector at subwavelength scales. According to their research, selective near-field coupling in HMMs is enabled by discrete electric dipoles with different phases, which serve as a metasource composed of all-electric components and with a symmetry-associated inner freedom.
Their research not only addresses the need for an all-electric experimental design scheme for near-field photonics, but also contributes fundamentally valuable symmetry-based excitation principles. Using a Huygens metasource, the researchers were able to observe the unidirectional excitation of hyperbolic bulk modes in a planar HMM. They found that unidirectional excitation in free space is the same as in the vertical direction, but opposite to that in the horizontal direction. These different propagation characteristics in horizontal and vertical directions are unique to the hyperbolic modes. In addition, the researchers used spin metasources to study the directional propagation of light in a planar hyperbolic waveguide. They found that, for the clockwise-rotating spin metasource, only the guided mode propagating from right to left is excited. And for the counterclockwise-rotating source, only the guided mode propagating from left to right is excited.
Overall, the research advances the fields of optical science and information communication, as the results provide the necessary conditions for highly efficient and experimentally verified photonics routing. For emerging applications in integrated optical devices, as well as wireless power transfer, switching, and filtering, this work promises unprecedented flexible control of near-field light.
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Materials provided by SPIE–International Society for Optics and Photonics. Note: Content may be edited for style and length. More

Quantum technologies are based on quantum properties of light, electrons, and atoms. In recent decades, scientists have learned to master these phenomena and exploit them in applications. Thus, the construction of a quantum computer for commercial applications is also coming within reach. One of the emerging technologies that is currently being advanced very successfully is ion trap quantum computers. Here, charged particles are trapped with electromagnetic fields in a vacuum chamber and prepared in such a way that they can serve as carriers for information and be used for computing, which includes cooling them to the lowest temperatures permitted by quantum mechanics. However, the quantum mechanical properties exploited in this process are highly error prone. Even the smallest deficiencies can heat up the strongly cooled particles and thereby lead to errors in the processing of quantum information.
Possible sources of such faults are weakly conducting or non-conducting materials, which are used, for example, as insulators in a metallic ion trap, or optics, which are necessary for coupling ions with laser light. “Even for ion traps made exclusively of metal, oxide layers on the metals would cause such failures,” explains Tracy Northup at the Department of Experimental Physics of the University of Innsbruck in Austria. Northups team together with collaborators in Innsbruck and in the U.S. have found a way to determine the influence of dielectric materials on the charged particles in ion traps.
Experimentally confirmed
This was achieved because the Innsbruck quantum physicists have an ion trap in which they can precisely set the distance between the ions and dielectric optics. Based on an earlier proposal by Rainer Blatt’s group, the physicists computed the amount of noise caused by the dielectric material for this ion trap and compared it with data from experiment. “Theory and experiment agree very well, confirming that this method is well suited for determining the influence of dielectric materials on the ions,” explains Markus Teller from the Innsbruck team. To calculate the noise, the so-called fluctuation-dissipation theorem from statistical physics was used, which mathematically describes the response of a system in thermal equilibrium to a small external perturbation.
“In quantum computers, there are many possible sources of noise, and it is very difficult to sort out the exact sources,” says Tracy Northup. “Our method is the first to quantify the influence of dielectric materials in a given ion trap on the charged particles. In the future, designers of ion trap quantum computers will be able to assess this effect much more accurately and design their devices to minimize these perturbations.” After having successfully demonstrated the method on their own ion trap, the Innsbruck physicists now want to apply it to the ion traps of collaborators in the U.S. and Switzerland.
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The future of quantum computing may depend on the further development and understanding of semiconductor materials known as transition metal dichalcogenides (TMDCs). These atomically thin materials develop unique and useful electrical, mechanical, and optical properties when they are manipulated by pressure, light, or temperature.
In research published today in Nature Communications, engineers from Rensselaer Polytechnic Institute demonstrated how, when the TMDC materials they make are stacked in a particular geometry, the interaction that occurs between particles gives researchers more control over the devices’ properties. Specifically, the interaction between electrons becomes so strong that they form a new structure known as a correlated insulating state. This is an important step, researchers said, toward developing quantum emitters needed for future quantum simulation and computing.
“There is something exciting going on,” said Sufei Shi, an assistant professor of chemical and biological engineering at Rensselaer, who led this work. “One of the quantum degrees of freedom that we hope to use in quantum computing is enhanced when this correlated state exists.”
Much of Shi’s research has focused on gaining a better understanding of the potential of the exciton, which is formed when an electron, excited by light, bonds with a hole — a positively charged version of the electron. Shi and his team have demonstrated this phenomenon in TMDC devices made of layers of Tungsten disulfide (WS2) and Tungsten diselenide (WSe2). Recently, the team also observed the creation of an interlayer exciton, which is formed when an electron and hole exist in two different layers of material. The benefit of this type of exciton, Shi said, is that it holds a longer lifetime and responds more significantly to an electric field — giving researchers greater ability to manipulate its properties.
In their latest research, Shi and his team showed how, by stacking TMDCs in a particular manner, they can develop a lattice known as a moiré superlattice. Picture two sheets of paper stacked on top of one another, each with the same pattern of hexagons cut out of them. If you were to shift the angle of one of the pieces of paper, the hexagons would no longer perfectly match up. The new formation is similar to that of a moiré superlattice.
The benefit of such a geometry, Shi said, is that it encourages electrons and interlayer excitons to bond together, further increasing the amount of control researchers have over the excitons themselves. This discovery, Shi said, is an important step toward developing quantum emitters that will be needed for future quantum simulation and quantum computing.
“It has essentially opened the door to a new world. We see a lot of things already, just by peeking through the door, but we have no idea what is going to happen if we open the door and get inside,” Shi said. “That is what we want to do, we want to open the door and get inside.”
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