Aurelia Butler

The concept of smart cities is founded on sophisticated cellular networks that would not only connect humans in the future but also humans to other smart devices. However, this would also require huge energy consumption. In the wake of climate change, this can make matters worse for our environment by increasing the greenhouse gas emissions. Thus, we not only need smart cities but also greener smart cities.
One way to address this issue is by switching off base stations (BSs), radio transmitters/receivers that serve as the hub of the local wireless network, when they have little to no traffic load. Laboratory testing has shown that active BSs consume as much as 60% of the maximum energy consumption even under no traffic load and switching them off can bring it down to 40%. However, there is a trade-off: putting BSs to sleep makes their traffic logs unavailable, which also reduces the accuracy of traffic prediction. Is there a way to avoid this compromise between accuracy and sustainability?
The answer, according to a new study, seems to be “yes.” The study, led by Professor Ryoichi Shinkuma from Shibaura Institute of Technology (SIT), Japan, and his colleagues, Associate Professor Kaoru Ota from Muroran Institute of Technology, Japan and Associate Professor Takehiro Sato from Kyoto University, Japan, proposed a novel scheme that not only reduced energy consumption but demonstrated a higher traffic prediction accuracy compared to the benchmark schemes! This paper was published in Volume 35, Issue 6 of the journal IEEE Network Magazine on November/December 2021.
How did the researchers achieve this remarkable feat? Prof. Shinkuma explains, “We applied software defined network (SDN) and edge computing to a cellular network such that each BS is equipped with an SDN switch, and an SDN controller can turn off any BS according to the traffic prediction results. An edge server collects the traffic logs through the SDN switches and predicts traffic volume using machine learning (ML).”
The ML method used by the researchers decided which BSs could be put into “sleep mode” based on the importance of their traffic logs in improving the prediction accuracy. Thus, BSs with low contribution to the accuracy for previous time slots were put to sleep at the next slot to save energy.
To validate their scheme, the researchers used real-world mobile traffic data collected over two months and compared its performance against that of two benchmark schemes. To their delight, the new scheme outperformed the benchmark schemes in its robustness against reducing the number of active BSs and different BS sets.
Could this study be a harbinger of greener cellular networks and smart cities? Prof. Shinkuma is optimistic. “By intelligently controlling the operation of BSs, renewable energy sources could be used to power future networks and, depending on the availability of renewable energy resource, the sleep schedules of the BSs can be determined,” he speculates.
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Physicists from the University of Amsterdam have proposed a new architecture for a scalable quantum computer. Making use of the collective motion of the constituent particles, they were able to construct new building blocks for quantum computing that pose fewer technical difficulties than current state-of-the art methods. The results were recently published in Physical Review Letters.
The researchers work at QuSoft and the Institute of Physics in the groups of Rene Gerritsma and Arghavan Safavi-Naini. The effort, which was led by the PhD candidate Matteo Mazzanti, combines two important ingredients. One is a so-called trapped-ion platform, one of the most promising candidates for quantum computing that makes use of ions — atoms that have either a surplus or a shortage of electrons and as a result are electrically charged. The other is the use of a clever method to control the ions supplied by optical tweezers and oscillating electric fields.
As the name suggests, trapped-ion quantum computers use a crystal of trapped ions. These ions can move individually, but more importantly, also as a whole. As it turns out, the possible collective motions of the ions facilitate the interactions between individual pairs of ions. In the proposal, this idea is made concrete by applying a uniform electric field to the whole crystal, in order to mediate interactions between two specific ions in that crystal. The two ions are selected by applying tweezer potentials on them — see the image above. The homogeneity of the electric field assures that it will only allow the two ions to move together with all other ions in the crystal. As a result, the interaction strength between the two selected ions is fixed, regardless of how far apart the two ions are.
A quantum computer consists of ‘gates’, small computational building blocks that perform quantum analogues of operations like ‘and’ and ‘or’ that we know from ordinary computers. In trapped-ion quantum computers, these gates act on the ions, and their operation depends on the interactions between these particles. In the above setup, the fact that those interactions do not depend on the distance means that also the duration of operation of a gate is independent of that distance. As a result, this scheme for quantum computing is inherently scalable, and compared to other state-of-the-art quantum computing schemes poses fewer technical challenges for achieving comparably well-operating quantum computers.
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A team of mathematicians and physicists has discovered how ice formations are shaped by external forces, such as water temperature. Its newly published research may offer another means for gauging factors that cause ice to melt.
“The shapes and patterning of ice are sensitive indicators of the environmental conditions at which it melted, allowing us to ‘read’ the shape to infer factors such as the ambient water temperature,” explains Leif Ristroph, an associate professor at New York University’s Courant Institute of Mathematical Sciences and one of the authors of the paper, which appears in the journal Physical Review Letters.
“Our work helps to understand how melting induces unusual flow patterns that in turn affect melting, which is one of the many complexities affecting the ice on our planet,” adds author Alexandra Zidovska, an associate professor in NYU’s Department of Physics.
The paper’s other authors were Scott Weady, an NYU graduate student, and Josh Tong, an undergraduate in NYU’s College of Arts and Science at the time of the study.
In NYU’s Applied Mathematics Laboratory and Center for Soft Matter Research, the researchers studied, through a series of experiments, the melting of ice in water and, in particular, how the water temperature affects the eventual shapes and patterning of ice. To do so, they created ultra-pure ice, which is free of bubbles and other impurities. The team recorded the melting of ice submerged into water tanks in a “cold room,” which is similar to a walk-in refrigerator whose temperature is controlled and varied.
“We focused on the cold temperatures — 0 to 10 degrees Celsius — at which ice in natural waters typically melts, and we found a surprising variety of shapes that formed,” says Ristroph, who directs the Applied Mathematics Laboratory. More

Researchers at the Yale School of Public Health were able to accurately predict outbreaks of COVID-19 in Connecticut municipalities using anonymous location information from mobile devices, according to a new study published in Science Advances.
The novel analysis applied in the study could help health officials stem community outbreaks of COVID-19 and allocate testing resources more efficiently, the researchers said.
The study was conducted by data scientists and epidemiologists from the Yale School of Public Health, the Connecticut Department of Public Health, the U.S. Centers for Disease Control and Prevention and Whitespace Ltd., a spatial data analytics firm.
The key to the findings was the precision with which researchers were able to identify incidents of high frequency close personal contact (defined as a radius of 6 feet) in Connecticut down to the municipal level. The CDC advises people to keep at least six feet of distance with others to avoid possible transmission of COVID-19.
“Close contact between people is the primary route for transmission of SARS-CoV-2, the virus that causes COVID-19,” said the study’s lead author Forrest Crawford, an associate professor of biostatistics at the Yale School of Public Health and an associate professor of ecology and evolutionary biology, management, statistics and data science at Yale.
“We measured close interpersonal contact within a 6-foot radius everywhere in Connecticut using mobile device geolocation data over the course of an entire year,” Crawford said. “This effort gave Connecticut epidemiologists and policymakers insight to people’s social distancing behavior statewide.”
Other studies have used so-called “mobility metrics” as proxy measures for social distancing behavior and potential COVID-19 transmission. But that analysis can be flawed. More

Surveys that ask too many of the same type of question tire respondents and return unreliable data, according to a new UC Riverside-led study.
The study found that people tire from questions that vary only slightly and tend to give similar answers to all questions as the survey progresses. Marketers, policymakers, and researchers who rely on long surveys to predict consumer or voter behavior will have more accurate data if they craft surveys designed to elicit reliable, original answers, the researchers suggest.
“We wanted to know, is gathering more data in surveys always better, or could asking too many questions lead to respondents providing less useful responses as they adapt to the survey,” said first author Ye Li, a UC Riverside assistant professor of management. “Could this paradoxically lead to asking more questions but getting worse results?”
While it may be tempting to assume more data is always better, the authors wondered if the decision processes respondents use to answer a series of questions might change, especially when those questions use a similar, repetitive format.
The research addressed quantitative surveys of the sort typically used in market research, economics, or public policy research that seek to understand people’s values about certain things. These surveys often ask a large number of structurally similar questions.
Researchers analyzed four experiments that asked respondents to answer questions involving choice and preference. More

Drilling with the beam of an electron microscope, scientists at the Department of Energy’s Oak Ridge National Laboratory precisely machined tiny electrically conductive cubes that can interact with light and organized them in patterned structures that confine and relay light’s electromagnetic signal. This demonstration is a step toward potentially faster computer chips and more perceptive sensors.
The seeming wizardry of these structures comes from the ability of their surfaces to support collective waves of electrons, called plasmons, with the same frequency as light waves but with much tighter confinement. The light-guiding structures are measured in nanometers, or billionths of a meter — 100,000 times thinner than a human hair.
“These nanoscale cube systems allow extreme confinement of light in specific locations and tunable control of its energy,” said ORNL’s Kevin Roccapriore, first author of a study published in the journal Small. “It’s a way to connect signals with very different length scales.”
The feat may prove critical for quantum and optical computing. Quantum computers encode information with quantum bits, or qubits, determined by a quantum state of a particle, such as its spin. Qubits can store many values compared with the single value stored by a classical bit.
Light — electromagnetic radiation that propagates by massless elementary particles called photons — replaces electrons as the messenger in optical computers. Because photons travel faster than electrons and do not generate heat, optical computers could have performance and energy efficiency superior to classical computers.
Future technologies may use the best of both worlds. More

Trapped ions excited with a laser beam can be used to create entangled qubits in quantum information systems, but addressing several stationary pairs of ions in a trap requires multiple optical switches and complex controls. Now, scientists at the Georgia Tech Research Institute (GTRI) have demonstrated the feasibility of a new approach that moves trapped ion pairs through a single laser beam, potentially reducing power requirements and simplifying the system.
In a paper scheduled to be published January 31 in the journal Physical Review Letters, the researchers describe implementing two-qubit entangling gates by moving calcium ions held in a surface electrode trap through a stationary bichromatic optical beam. Maintaining a constant Doppler shift during the ion movement required precise control of the timing.
“We’ve shown that ion transport is an interesting tool that can be applied in unique ways to produce an entangled state using fine control over the ion transport,” said Holly Tinkey, a GTRI research scientist who led the study. “Most ion trap experiments have some control over the motion of the ions, so what we have shown is that we can potentially integrate that existing transport into quantum logic operations.”
Measurements showed that the entangled quantum state of the two qubits transported through the optical beam had a fidelity comparable to entangled states produced by stationary gates performed in the same trapping system. The experiment used an optical qubit transition between an electronic ground state and a metastable state of 40Ca+ ions within a surface trap, a setup which allowed both one-qubit and two-qubit gates to be performed using a single beam.
The researchers moved the pair of trapped ions by precisely varying the electrical confinement fields in the trap by controlling the voltages applied to adjacent electrodes. The ions themselves have an electrical charge, a property which makes them subject to the changing electrical fields around them.
“We perform some interactions where the ions are trapped together in a single potential well and where they are very close and can interact, but then we sometimes want to separate them to do something distinct to one ion that we don’t want to do to the other ion,” Tinkey explained. More

A joint research team from the Hong Kong University of Science and Technology (HKUST) and the University of Tokyo discovered an unusual topological aspect of sodium chloride, commonly known as table salt, which will not only facilitate the understanding of the mechanism behind salt’s dissolution and formation, but may also pave the way for the future design of nanoscale conducting quantum wires.
There is a whole variety of advanced materials in our daily life, many gadgets and technology are created through the assembly of different materials. Cellphone, for example, adopted a combination of many different substances — glass for the monitor, aluminum alloy for the frame, and metals like gold, silver and copper for its internal wirings. But nature has its own genius way of ‘cooking’ different properties into one wonder material, or what is known as ‘topological material’.
Topology, as a mathematical concept, studies what aspects of an object are robust under a smooth deformation. For instance, we can squeeze, stretch, or twist a T-shirt, but the number its openings would still remain as four so long as we do not tear it apart. The discovery of topological phases of matter, highlighted by the 2016 Nobel Prize in Physics, suggests that certain quantum materials are inherently a combination of electrical insulator and conductor. This could necessitate a conducting boundary even when the bulk of the material is insulating. Such materials are neither classified as a metal nor an insulator, but a natural assembly of the two.
While the topological qualities of materials attract a lot of research interests, at present they are only realized in an exclusive set of exotic materials — such as the two-dimensional graphene. However, in a recent work, Prof. Adrian PO Hoi Chun, Assistant Professor from HKUST’s Department of Physics and his collaborator, Prof. Haruki WATANABE from the University of Tokyo, have discovered a surprising connection between topology and a large class of ordinary substances, including table salt.
Table salt, or sodium chloride, is one of the most common crystals frequently featured in high-school chemistry textbooks as a prototypical ionic compound. It’s long believed that such well-known substance are topologically boring. However, the research team discovered that table salt can actually, in theory, realize a form of recently introduced, “higher-order” topology. Instead of conducting two-dimensional surfaces or one-dimensional edges, the zero-dimensional corner of a grain of salt showcases an anomalous behavior in which electric charges are effectively fractionalized into one-eighth of the fundamental unit of Nature. Furthermore, the robustness of this topological property implies that even if the chemical structure is modified into other formats such as silver chloride or potassium fluoride, the result would still be upheld.
Prof. Watanabe said the connection between topological materials and everyday substances like table salt is totally unexpected. Prof. Po said the result suggests an overlooked aspect of topology in common ionic compounds. “The finding may inspire future design of nanoscale conducting quantum wires, or novel drug delivery method, which is so often studied along with the salt dissolution processes,” Prof. Po said, adding that “it is amusing to realize how we ingest fractions of an electron upon our every meal.”
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