Computers Math

Researchers have reported a new form of electronics known as ‘drawn-on-skin electronics,’ allowing multifunctional sensors and circuits to be drawn on the skin with an ink pen. More

Researchers have solved a major problem for optical wireless communications — the process by which light carries information between cell phones and other devices. Light-emitting diodes (LEDs) pulse their light in a coded message that recipient devices can understand.
Now, a team of researchers based in Japan has married the two options into the ideal combination of long lasting and fast LEDs. They published their results on July 22 in Applied Physics Letters.
“A key technology for faster modulation is to decrease the device si earch for Advanced Materials at Tohoku University. “However, this tactic creates a dilemma: although smaller LEDs can be modulated faster, they have lower power.”
Another issue is that both visible and infrared optical wireless communications can have significant solar interference, according to Kojima. To avoid confusion with visible and infrared solar light, the researchers aimed to improve LEDs that specifically communicate via deep ultraviolet light, which can be detected without solar interference.
“Deep ultraviolet LEDs are currently mass produced in factories for applications related to COVID-19,” Kojima said, noting that deep ultraviolet light is used for sterilization processes as well as in solar-blind optical wireless communications. “So, they’re cheap and practical to use.”
The researchers fabricated the deep ultraviolet LEDs on sapphire templates, which are considered an inexpensive substrate, and measured their transmission speed. They found that the deep ultraviolet LEDs were smaller and much quicker in their communications than traditional LEDs at that speed.
“The mechanism underlying this speed is in how a lot of tiny LEDs self-organize in a single deep ultraviolet LED,” Kojima said. “The tiny LED ensemble helps with both power and speed.”
The researchers want to use the deep ultraviolet LEDs in 5G wireless networks. Many technologies are currently under testing to contribute 5G, and Li-Fi, or light fidelity, is one of the candidate technologies.
“Li-Fi’s critical weakness is its solar dependency,” Kojima said. “Our deep ultraviolet LED-based optical wireless technology can compensate for this problem and contribute to society, I hope.”
This work was supported in part by Five-Star Alliance and the Japan Society for the Promotion of Science.

Story Source:
Materials provided by Tohoku University. Note: Content may be edited for style and length. More

A way of shrinking the devices used in quantum sensing systems has been developed by researchers at the UK Quantum Technology Hub Sensors and Timing, which is led by the University of Birmingham.
Sensing devices have a huge number of industrial uses, from carrying out ground surveys to monitoring volcanoes. Scientists working on ways to improve the capabilities of these sensors are now using quantum technologies, based on cold atoms, to improve their sensitivity.
Machines developed in laboratories using quantum technology, however, are cumbersome and difficult to transport, making current designs unsuitable for most industrial uses.
The team of researchers has used a new approach that will enable quantum sensors to shrink to a fraction of their current size. The research was conducted by an international team led by University of Birmingham and SUSTech in China in collaboration with Paderborn University in Germany. Their results are published in Science Advances.
The quantum technology currently used in sensing devices works by finely controlling laser beams to engineer and manipulate atoms at super-cold temperatures. To manage this, the atoms have to be contained within a vacuum-sealed chamber where they can be cooled to the desired temperatures.
A key challenge in miniaturising the instruments is in reducing the space required by the laser beams, which typically need to be arranged in three pairs, set at angles. The lasers cool the atoms by firing photons against the moving atom, lowering its momentum and therefore cooling it down.
The new findings show how a new technique can be used to reduce the space needed for the laser delivery system. The method uses devices called optical metasurfaces — manufactured structures that can be used to control light.
A metasurface optical chip can be designed to diffract a single beam into five separate, well-balanced and uniform beams that are used to supercool the atoms. This single chip can replace the complex optical devices that currently make up the cooling system.
Metasurface photonic devices have inspired a range of novel research activities in the past few years and this is the first time researchers have been able to demonstrate its potential in cold atom quantum devices.
Dr Yu-Hung Lien, lead author of the study, says: “The mission of the UK Quantum Technology Hub is to deliver technologies that can be adopted and used by industry. Designing devices that are small enough to be portable or which can fit into industrial processes and practices is vital. This new approach represents a significant step forward in this approach.”
The team have succeeded in producing an optical chip that measures just 0.5mm across, resulting in a platform for future sensing devices measuring about 30cm cubed. The next step will be to optimise the size and the performance of the platform to produce the maximum sensitivity for each application.

Story Source:
Materials provided by University of Birmingham. Note: Content may be edited for style and length. More

Researchers have solved a 20-year-old problem in quantum information theory on how to calculate entanglement cost — a way to measure entanglement — in a manner that’s efficiently computable, useful, and broadly applicable in several quantum research areas. More

A typical recycling process converts large quantities of items made of a single material into more of the same. However, this approach isn’t feasible for old electronic devices, or “e-waste,” because they contain small amounts of many different materials that cannot be readily separated. Now, in ACS Omega, researchers report a selective, small-scale microrecycling strategy, which they use to convert old printed circuit boards and monitor components into a new type of strong metal coating.
In spite of the difficulty, there’s plenty of reason to recycle e-waste: It contains many potentially valuable substances that can be used to modify the performance of other materials or to manufacture new, valuable materials. Previous research has shown that carefully calibrated high temperature-based processing can selectively break and reform chemical bonds in waste to form new, environmentally friendly materials. In this way, researchers have already turned a mix of glass and plastic into valuable, silica-containing ceramics. They’ve also used this process to recover copper, which is widely used in electronics and elsewhere, from circuit boards. Based on the properties of copper and silica compounds, Veena Sahajwalla and Rumana Hossain suspected that, after extracting them from e-waste, they could combine them to create a durable new hybrid material ideal for protecting metal surfaces.
To do so, the researchers first heated glass and plastic powder from old computer monitors to 2,732 F, generating silicon carbide nanowires. They then combined the nanowires with ground-up circuit boards, put the mix on a steel substrate then heated it up again. This time the thermal transformation temperature selected was 1,832 F, melting the copper to form a silicon-carbide enriched hybrid layer atop the steel. Microscope images revealed that, when struck with a nanoscale indenter, the hybrid layer remained firmly affixed to the steel, without cracking or chipping. It also increased the steel’s hardness by 125%. The team refers to this targeted, selective microrecycling process as “material microsurgery,” and say that it has the potential to transform e-waste into advanced new surface coatings without the use of expensive raw materials.

Story Source:
Materials provided by American Chemical Society. Note: Content may be edited for style and length. More

Extensive power outages and satellite blackouts that affect air travel and the internet are some of the potential consequences of massive solar storms. These storms are believed to be caused by the release of enormous amounts of stored magnetic energy due to changes in the magnetic field of the sun’s outer atmosphere — something that until now has eluded scientists’ direct measurement. Researchers believe this recent discovery could lead to better “space weather” forecasts in the future.
“We are becoming increasingly dependent on space-based systems that are sensitive to space weather. Earth-based networks and the electrical grid can be severely damaged if there is a large eruption,” says Tomas Brage, Professor of Mathematical Physics at Lund University in Sweden.
Solar flares are bursts of radiation and charged particles, and can cause geomagnetic storms on Earth if they are large enough. Currently, researchers focus on sunspots on the surface of the sun to predict possible eruptions. Another and more direct indication of increased solar activity would be changes in the much weaker magnetic field of the outer solar atmosphere — the so-called Corona.
However, no direct measurement of the actual magnetic fields of the Corona has been possible so far.
“If we are able to continuously monitor these fields, we will be able to develop a method that can be likened to meteorology for space weather. This would provide vital information for our society which is so dependent on high-tech systems in our everyday lives,” says Dr Ran Si, post-doc in this joint effort by Lund and Fudan Universities.
The method involves what could be labelled a quantum-mechanical interference. Since basically all information about the sun reaches us through “light” sent out by ions in its atmosphere, the magnetic fields must be detected by measuring their influence on these ions. But the internal magnetic fields of ions are enormous — hundreds or thousands of times stronger than the fields humans can generate even in their most advanced labs. Therefore, the weak coronal fields will leave basically no trace, unless we can rely on this very delicate effect — the interference between two “constellations” of the electrons in the ion that are close — very close — in energy.
The breakthrough for the research team was to predict and analyze this “needle in the haystack” in an ion (nine times ionized iron) that is very common in the corona.
The work is based on state-of-the art calculations performed in the Mathematical Physics division of Lund University and combined with experiments using a device that could be thought of as being able to produce and capture small parts of the solar corona — the Electron Beam Ion Trap, EBIT, in Professor Roger Hutton’s group in Fudan University in Shanghai.
“That we managed to find a way of measuring the relatively weak magnetic fields found in the outer layer of the sun is a fantastic breakthrough,” concludes Tomas Brage.

Story Source:
Materials provided by Lund University. Note: Content may be edited for style and length. More

The possibility of achieving room temperature superconductivity took a tiny step forward with a recent discovery by a team of P physicists and materials scientists. More

Using a quantum computer to simulate time travel, researchers have demonstrated that, in the quantum realm, there is no “butterfly effect.” In the research, information — qubits, or quantum bits — “time travel” into the simulated past. One of them is then strongly damaged, like stepping on a butterfly, metaphorically speaking. Surprisingly, when all qubits return to the “present,” they appear largely unaltered, as if reality is self-healing.
“On a quantum computer, there is no problem simulating opposite-in-time evolution, or simulating running a process backwards into the past,” said Nikolai Sinitsyn, a theoretical physicist at Los Alamos National Laboratory and coauthor of the paper with Bin Yan, a post doc in the Center for Nonlinear Studies, also at Los Alamos. “So we can actually see what happens with a complex quantum world if we travel back in time, add small damage, and return. We found that our world survives, which means there’s no butterfly effect in quantum mechanics.”
In Ray Bradbury’s 1952 science fiction story, “A Sound of Thunder,” a character used a time machine to travel to the deep past, where he stepped on a butterfly. Upon returning to the present time, he found a different world. This story is often credited with coining the term “butterfly effect,” which refers to the extremely high sensitivity of a complex, dynamic system to its initial conditions. In such a system, early, small factors go on to strongly influence the evolution of the entire system.
Instead, Yan and Sinitsyn found that simulating a return to the past to cause small local damage in a quantum system leads to only small, insignificant local damage in the present.
This effect has potential applications in information-hiding hardware and testing quantum information devices. Information can be hidden by a computer by converting the initial state into a strongly entangled one.
“We found that even if an intruder performs state-damaging measurements on the strongly entangled state, we still can easily recover the useful information because this damage is not magnified by a decoding process,” Yan said. “This justifies talks about creating quantum hardware that will be used to hide information.”
This new finding could also be used to test whether a quantum processor is, in fact, working by quantum principles. Since the newfound no-butterfly effect is purely quantum, if a processor runs Yan and Sinitsyn’s system and shows this effect, then it must be a quantum processor.

advertisement

To test the butterfly effect in quantum systems, Yan and Sinitsyn used theory and simulations with the IBM-Q quantum processor to show how a circuit could evolve a complex system by applying quantum gates, with forwards and backwards cause and effect.
Presto, a quantum time-machine simulator.
In the team’s experiment, Alice, a favorite stand-in agent used for quantum thought experiments, prepares one of her qubits in the present time and runs it backwards through the quantum computer. In the deep past, an intruder — Bob, another favorite stand-in — meaures Alice’s qubit. This action disturbs the qubit and destroys all its quantum correlations with the rest of the world. Next, the system is run forward to the present time.
According to Ray Bradbury, Bob’s small damage to the state and all those correlations in the past should be quickly magnified during the complex forward-in-time evolution. Hence, Alice should be unable to recover her information at the end.
But that’s not what happened. Yan and Sinitsyn found that most of the presently local information was hidden in the deep past in the form of essentially quantum correlations that could not be damaged by minor tampering. They showed that the information returns to Alice’s qubit without much damage despite Bob’s interference. Counterintuitively, for deeper travels to the past and for bigger “worlds,” Alice’s final information returns to her even less damaged.
“We found that the notion of chaos in classical physics and in quantum mechanics must be understood differently,” Sinitsyn said. More