Computers Math

Physicists from Exeter and Trondheim have developed a theory describing how space reflection and time reversal symmetries can be exploited, allowing for greater control of transport and correlations within quantum materials.
Two theoretical physicists, from the University of Exeter (United Kingdom) and the Norwegian University of Science and Technology (in Trondheim, Norway), have built a quantum theory describing a chain of quantum resonators satisfying space reflection and time reversal symmetries. They have shown how the different quantum phases of such chains are associated with remarkable phenomena, which may be useful in the design of future quantum devices relying on strong correlations.
A common distinction in physics is between open and closed systems. Closed systems are isolated from any external environment, such that energy is conserved because there is nowhere for it to escape to. Open systems are connected to the outer world, and via exchanges with the environment they are subject to energy gains and energy losses. There is an important third case. When the energy flowing in and flowing out of the system is finely balanced, an intermediate situation between being open and closed arises. This equilibrium can occur when the system obeys a combined symmetry of space and time, that is when (1) switching left and right and (2) flipping the arrow of time leave the system essentially unchanged.
In their latest research, Downing and Saroka discuss the phases of a quantum chain of resonators satisfying space reflection and time reversal symmetries. There are principally two phases of interest, a trivial phase (accompanied by intuitive physics) and a nontrivial phase (marked with surprising physics). The border between these two phases is marked by an exceptional point. The researchers have found the locations of these exceptional points for a chain with an arbitrary number of resonators, providing insight into the scaling up of quantum systems obeying these symmetries. Importantly, the nontrivial phase allows for unconventional transport effects and strong quantum correlations, which may be used to control the behaviour and propagation of light at nanoscopic length scales.
This theoretical study may be useful for the generation, manipulation and control of light in low-dimensional quantum materials, with a view to building light-based devices exploiting photons, the particles of light, as workhorses down at sizes around one billionth of a meter.
Charles Downing, from the University of Exeter, commented: “Our work on parity-time symmetry in open quantum systems further emphasises how symmetry underpins our understanding of the physical world, and how we may benefit from it.”
Vasil Saroka, from the Norwegian University of Science and Technology, added: “We hope that our theoretical work on parity-time symmetry can inspire further experimental research in this exciting area of physics.”
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A floating, robotic film designed at UC Riverside could be trained to hoover oil spills at sea or remove contaminants from drinking water.
Powered by light and fueled by water, the film could be deployed indefinitely to clean remote areas where recharging by other means would prove difficult.
“Our motivation was to make soft robots sustainable and able to adapt on their own to changes in the environment. If sunlight is used for power, this machine is sustainable, and won’t require additional energy sources,” said UCR chemist Zhiwei Li. “The film is also re-usable.”
Researchers dubbed the film Neusbot after neustons, a category of animals that includes water striders. These insects traverse the surface of lakes and slow-moving streams with a pulsing motion, much like scientists have been able to achieve with the Neusbot, which can move on any body of water.
While other scientists have created films that bend in response to light, they have not been able to generate the adjustable, mechanical oscillation of which Neusbot is capable. This type of motion is key to controlling the robot and getting it to function where and when you want.
Technical details of this achievement are described in a new Science Robotics paper. More

In research published in the journal Cell Systems, Professor Lenore Cowen of the Tufts Department of Computer Science and colleagues from Massachusetts Institute of Technology (MIT) collaborated to design a structurally-motivated deep learning method built from recent advances in neural language modeling. The team’s deep-learning model, called D-SCRIPT, was able to predict protein-protein interactions (PPIs) from primary amino acid sequences.
Those predictions allow researchers to model PPI networks with a clustering method and enable the detection of functional subnetworks, or modules. Scientists study organisms’ PPI networks as a means of understanding their signaling circuitry, which could lead to better prediction of cell behavior and gene functions, while finding functional modules in PPI networks could help researchers reach stronger understandings of cellular functional organization.
Cowen along with researchers Sam Sledzieski, Rohit Singh, and renowned computational biologist Bonnie Berger from MIT’s Computer Science and Artificial Intelligence Lab found that the D-SCRIPT model, trained on more than 38,000 human PPIs, was better able to generalize when compared to the current state-of-the-art approach (the deep-learning method PIPR), and therefore could characterize fly proteins. They also applied D-SCRIPT to screen for PPIs related to cow digestion and identified functional gene modules that related to immune response and metabolism.
The researchers concluded that the D-SCRIPT model trained on human PPI data could be applied to many species of interest — critically, even those that have been rarely studied or that lack PPI data.
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In 1973, physicist Philip W. Anderson theorized the existence of a new state of matter that has been a major focus of the field, especially in the race for quantum computers.
This bizarre state of matter is called a quantum spin liquid and, contrary to the name, has nothing to do with everyday liquids like water. Instead, it’s all about magnets that never freeze and the way electrons in them spin. In regular magnets, when the temperature drops below a certain temperature, the electrons stabilize and form a solid piece of matter with magnetic properties. In quantum spin liquid, the electrons don’t stabilize when cooled, don’t form into a solid, and are constantly changing and fluctuating (like a liquid) in one of the most entangled quantum states ever conceived.
The different properties of quantum spin liquids have promising applications that can be used to advance quantum technologies such as high-temperature superconductors and quantum computers. But the problem about this state of matter has been its very existence. No one had ever seen it — at least, that had been the case for almost 50 years.
Today, a team of Harvard-led physicists said they have finally experimentally documented this long sought-after exotic state of matter. The work is described in a new study in the journal Science and marks a big step toward being able to produce this elusive state on demand and to gain a novel understanding of its mysterious nature.
“It is a very special moment in the field ,” said Mikhail Lukin, the George Vasmer Leverett Professor of Physics, co-director of the Harvard Quantum Initiative (HQI), and one of the senior authors of the study. “You can really touch, poke, and prod at this exotic state and manipulate it to understand its properties. …It’s a new state of matter that people have never been able to observe.”
The learnings from this science research could one day provide advancements for designing better quantum materials and technology. More specifically, the exotic properties from quantum spin liquids could hold the key to creating more robust quantum bits — known as topological qubits — that are expected to be resistant to noise and external interference. More

Detecting light beyond the visible red range of our eyes is hard to do, because infrared light carries so little energy compared to ambient heat at room temperature. This obscures infrared light unless specialised detectors are chilled to very low temperatures, which is both expensive and energy-intensive.
Now researchers led by the University of Cambridge have demonstrated a new concept in detecting infrared light, showing how to convert it into visible light, which is easily detected.
In collaboration with colleagues from the UK, Spain and Belgium, the team used a single layer of molecules to absorb the mid-infrared light inside their vibrating chemical bonds. These shaking molecules can donate their energy to visible light that they encounter, ‘upconverting’ it to emissions closer to the blue end of the spectrum, which can then be detected by modern visible-light cameras.
The results, reported in the journal Science, open up new low-cost ways to sense contaminants, track cancers, check gas mixtures, and remotely sense the outer universe.
The challenge faced by the researchers was to make sure the quaking molecules met the visible light quickly enough. “This meant we had to trap light really tightly around the molecules, by squeezing it into crevices surrounded by gold,” said first author Angelos Xomalis from Cambridge’s Cavendish Laboratory.
The researchers devised a way to sandwich single molecular layers between a mirror and tiny chunks of gold, only possible with ‘meta-materials’ that can twist and squeeze light into volumes a billion times smaller than a human hair.
“Trapping these different colours of light at the same time was hard, but we wanted to find a way that wouldn’t be expensive and could easily produce practical devices,” said co-author Dr Rohit Chikkaraddy from the Cavendish Laboratory, who devised the experiments based on his simulations of light in these building blocks.
“It’s like listening to slow-rippling earthquake waves by colliding them with a violin string to get a high whistle that’s easy to hear, and without breaking the violin,” said Professor Jeremy Baumberg of the NanoPhotonics Centre at Cambridge’s Cavendish Laboratory, who led the research.
The researchers emphasise that while it is early days, there are many ways to optimise the performance of these inexpensive molecular detectors, which then can access rich information in this window of the spectrum.
From astronomical observations of galactic structures to sensing human hormones or early signs of invasive cancers, many technologies can benefit from this new detector advance.
The research was conducted by a team from the University of Cambridge, KU Leuven, University College London (UCL), the Faraday Institution, and Universitat Politècnica de València.
The research is funded as part of a UK Engineering and Physical Sciences Research Council (EPSRC) investment in the Cambridge NanoPhotonics Centre, as well as the European Research Council (ERC), Trinity College Cambridge and KU Leuven.
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When two superconducting regions are separated by a strip of non-superconducting material, a special quantum effect can occur, coupling both regions: The Josephson effect. If the spacer material is a half-metal ferromagnet novel implications for spintronic applications arise. An international team has now for the first time designed a material system that exhibits an unusually long-range Josephson effect: Here, regions of superconducting YBa2Cu3O7 are separated by a region of half-metallic, ferromagnetic manganite (La2/3Sr1/3MnO3) one micron wide.
With the help of magneto-transport measurements, the researchers were able to demonstrate the presence of a supercurrent circulating through the manganite — this supercurrent is arising from the superconducting coupling between both superconducting regions, and thus a manifestation of a Josephson effect with a macroscopic long range.
Extremely rare: Triplett superconductivity
In addition, the scientists explored another interesting property with profound consequences for spintronic applications. In superconductors electrons pair together in so-called Cooper pairs. In the vast majority of superconducting materials these pairs are composed by electrons with opposite spin in order to minimise the magnetic exchange field which is detrimental for the stabilisation of superconductivity. The ferromagnet used by the international team has been a half-ferromagnet for which only one spin type electron is allowed to circulate. The fact that a supercurrent has been detected within this material, implies that the Cooper pairs of this supercurrent must be composed by electrons having the same spin. This so-called “triplet” superconductivity is extremely rare.
Mapping magnetic domains at BESSY II
“At the XMCD-PEEM station at BESSY II, we mapped and measured the magnetic domains within the manganite spacer. We observed wide regions homogeneously magnetised and connecting the superconducting regions. Triplet spin pairs can propagate freely in these,” explains Dr. Sergio Valencia Molina, HZB physicist, who supervised the measurements at BESSY II.
Superconducting currents flow without resistance which make them very appealing for low-power consumption applications. In the present case this current is made of electrons with equal spins. Such spin polarised currents could be used in novel superconducting spintronic applications for the transport (over long distances) and reading/writing of information while profiting from the stability imposed by the macroscopic quantum coherence of the Josephson effect.
The new device made of the superconducting and ferromagnetic components therefore opens up opportunities for superconducting spintronics and new perspectives for quantum computing.
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Analysing molecular characteristics and their variation during lifestyle changes, by combining digital tools, classical laboratory tests and new biomolecular measurements, could enable individualised prevention of disease. This is according to a new study from Karolinska Institutet in Sweden and the University of Helsinki in Finland published in the journal Cell Systems. The researchers show what a proactive healthcare model could comprise and how it could help in maintaining good health.
Sensors, apps and other digital alternatives for monitoring health are increasing our ability to take proactive measures to improve our health and wellbeing. Moreover, the simultaneous measurement of numerous biomolecular variables (multiomics) enables deep and comprehensive profiling of human biology.
“Instead of focusing on the treatment of the later stages of disease, future healthcare services could focus on more proactive and individualised interventions and on the early detection of disease,” says the study’s first author Francesco Marabita, researcher at the Department of Oncology-Pathology, Karolinska Institutet and SciLifeLab in Sweden. “It might sound a little futuristic, but the technology is already there.”
The Digital Health Revolution (DHR) project is a multicentre study set up a few years ago by researchers, amongst other institutions, from the Institute for Molecular Medicine Finland (FIMM) at the University of Helsinki to explore and pilot future approaches to healthcare.
The study spanned 16 months and included 96 individuals between the ages of 25 and 59 who were registered at an occupational healthcare clinic in Helsinki, Finland. There were no known serious diseases, but some of the participants had risk factors such as high blood pressure, elevated glucose or obesity.
The molecular profiling was done in collaboration with investigators from Karolinska Institutet and SciLifeLab. In addition to extensive multiomics analyses, the serial data collection included online questionnaires, clinical laboratory measurements in blood samples, analysis of the gut microbiome, and activity and sleep data using a smart watch. More

More attention must be paid to improving perceptions of emerging technologies like AI-powered symptom checkers, which could ease the strain on health-care systems, according to a recent study.
Symptom checkers are online platforms that help with self-triage based on a range of inputted symptoms and demographic details.
The study, led by University of Waterloo researchers, found that “tech seekers,” people who are open to technology but perceive a lack of access to it, are the most likely to want to use the technology — more than “tech acceptors,” people who are both open to it and perceive it to be accessible.
The least likely group of people to adopt the tool are “tech rejectors,” those who do not view it as accessible and have a negative view of AI. In between were “skeptics,” who have concerns about trust and output quality, and “unsure acceptors,” who do not perceive access to be an issue but have negative perceptions about AI.
“These findings should be of great interest — or concern — to the three active arms of any health-care system that intends to use AI-driven symptom checkers: prospective patients, medical experts and developers of AI-driven symptom checkers,” said co-author Ashok Chaurasia, a professor in the School of Public Health Sciences. “This study highlights the need for more collaboration between these groups to improve AI models and their perception within the general population and medical experts.”
Stephanie Aboueid, the study’s lead author and a School of Public Health Sciences graduate, said, “This technology is very promising in the health-care sector, given that it has the potential to reduce unnecessary medical visits and address the lack of access to primary care providers.”
The researchers surveyed 1,305 university students aged 18 to 34 who had never used a symptom checker before the study. They gathered data on trust, usefulness, credibility, demonstrability, output quality, perspectives about AI, ease of use and accessibility for the analysis.
“Symptom checkers are important because they speak to the younger generation who value timeliness and convenience,” Aboueid said. “They are not just a fad, as we’ve seen with Babylon, for example, which recently went public and has been adopted by various health institutions.
Aboueid said the researchers used university-aged responders for the study because they are typically eager adopters of technology. Because of the age group studied, high education levels and good health status, additional studies are needed in other populations with wider age ranges, education and health levels, the researchers said.
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