Plasmons are oscillations in the plasma of free electrons that constantly swirl across the surface of conductive materials like metals. In some nanomaterials, a specific color of light can resonate with the plasma and cause the electrons inside it to lose their individual identities and move as one, in rhythmic waves. Rice’s Laboratory for Nanophotonics (LANP) has pioneered a growing list of plasmonic technologies for applications as diverse as color-changing glass, molecular sensing, cancer diagnosis and treatment, optoelectronics, solar energy collection and photocatalysis.
Reporting online in the Proceedings of the National Academy of Sciences, LANP scientists detailed the results of a two-year experimental and theoretical study of plasmons in three different polycyclic aromatic hydrocarbons (PAHs). Unlike the plasmons in relatively large metal nanoparticles, which can typically be described with classical electromagnetic theory like Maxwell’s [James Clerk Maxwell] equations, the paucity of atoms in the PAHs produces plasmons that can only be understood in terms of quantum mechanics, said study co-author and co-designer Naomi Halas, the director of LANP and the lead researcher on the project.
“These PAHs are essentially scraps of graphene that contain five or six fused benzene rings surrounded by a perimeter of hydrogen atoms,” Halas said. “There are so few atoms in each that adding or removing even a single electron dramatically changes their electronic behavior.”
Halas’ team had experimentally verified the existence of molecular plasmons in several previous studies. But an investigation that combined side by side theoretical and experimental perspectives was needed, said study co-author Luca Bursi, a postdoctoral research associate and theoretical physicist in the research group of study co-designer and co-author Peter Nordlander.
“Molecular excitations are a ubiquity in nature and very well studied, especially for neutral PAHs, which have been considered as the standard of non-plasmonic excitations in the past,” Bursi said. “Given how much is already known about PAHs, they were an ideal choice for further investigation of the properties of plasmonic excitations in systems as small as actual molecules, which represent a frontier of plasmonics.”
Lead co-author Kyle Chapkin, a Ph.D. student in applied physics in the Halas research group, said, “Molecular plasmonics is a new area at the interface between plasmonics and molecular chemistry, which is rapidly evolving. When plasmonics reach the molecular scale, we lose any sharp distinction of what constitutes a plasmon and what doesn’t. We need to find a new rationale to explain this regime, which was one of the main motivations for this study.”
In their native state, the PAHs that were studied — anthanthrene, benzo[ghi]perylene and perylene — are charge-neutral and cannot be excited into a plasmonic state by the visible wavelengths of light used in Chapkin’s experiments. In their anionic form, the molecules contain an additional electron, which alters their “ground state” and makes them plasmonically active in the visible spectrum. By exciting both the native and anionic forms of the molecules and comparing precisely how they behaved as they relaxed back to their ground states, Chapkin and Bursi built a solid case that the anionic forms do support molecular plasmons in the visible spectrum.
The key, Chapkin said, was identifying a number of similarities between the behavior of known plasmonic particles and the anionic PAHs. By matching both the timescales and modes for relaxation behaviors, the LANP team built up a picture of a characteristic dynamics of low-energy plasmonic excitations in the anionic PAHs.
“In molecules, all excitations are molecular excitations, but select excited states show some characteristics that allow us to draw a parallel with the well-established plasmonic excitations in metal nanostructures,” Bursi said.
“This study offers a window on the sometimes surprising behavior of collective excitations in few-atom quantum systems,” Halas said. “What we’ve learned here will aid our lab and others in developing quantum-plasmonic approaches for ultrafast color-changing glass, molecular-scale optoelectronics and nonlinear plasmon-mediated optics.”
Here’s a link to and a citation for the paper,
Lifetime dynamics of plasmons in the few-atom limit by Kyle D. Chapkin, Luca Bursi, Grant J. Stec, Adam Lauchner, Nathaniel J. Hogan, Yao Cui, Peter Nordlander, and Naomi J. Halas. PNAS September 11, 2018 115 (37) 9134-9139; published ahead of print August 27, 2018 DOI: https://doi.org/10.1073/pnas.1805357115
Great Pyramid of Giza and Sphinx [downloaded from http://news.ifmo.ru/en/science/photonics/news/7731/]
Russian and German scientists have taken a closer look at the Great Pyramid as they investigate better ways of designing sensors and solar cells. From a July 30, 2018 news item on Nanowerk,
An international research group applied methods of theoretical physics to investigate the electromagnetic response of the Great Pyramid to radio waves. Scientists predicted that under resonance conditions the pyramid can concentrate electromagnetic energy in its internal chambers and under the base. The research group plans to use these theoretical results to design nanoparticles capable of reproducing similar effects in the optical range. Such nanoparticles may be used, for example, to develop sensors and highly efficient solar cells.
While Egyptian pyramids are surrounded by many myths and legends, we have little scientifically reliable information about their physical properties. As it turns out, sometimes this information proves to be more fascinating than any fiction. This idea found confirmation in a new joint study undertaken by scientists from ITMO University and the Laser Zentrum Hannover. The physicists took an interest in how the Great Pyramid would interact with electromagnetic waves of a proportional, or resonant, length. Calculations showed that in the resonant state the pyramid can concentrate electromagnetic energy in its internal chambers as well as under its base, where the third unfinished chamber is located.
These conclusions were derived on the basis of numerical modeling and analytical methods of physics. The researchers first estimated that resonances in the pyramid can be induced by radio waves with a length ranging from 200 to 600 meters. Then they made a model of the electromagnetic response of the pyramid and calculated the extinction cross section. This value helps to estimate which part of the incident wave energy can be scattered or absorbed by the pyramid under resonant conditions. Finally, for the same conditions, the scientists obtained the electromagnetic fields distribution inside the pyramid.
In order to explain the results, the scientists conducted a multipole analysis. This method is widely used in physics to study the interaction between a complex object and electromagnetic field. The object scattering the field is replaced by a set of simpler sources of radiation: multipoles. The collection of multipoles radiation coincides with the field scattering by an entire object. Therefore, by knowing the type of each multipole, it is possible to predict and explain the distribution and configuration of the scattered fields in the whole system.
The Great Pyramid attracted the researchers’ attention while they were studying the interaction between light and dielectric nanoparticles. The scattering of light by nanoparticles depends on their size, shape, and refractive index of the source material. By varying these parameters, it is possible to determine the resonance scattering regimes and use them to develop devices for controlling light at the nanoscale.
“Egyptian pyramids have always attracted great attention. We as scientists were interested in them as well, and so we decided to look at the Great Pyramid as a particle resonantly dissipating radio waves. Due to the lack of information about the physical properties of the pyramid, we had to make some assumptions. For example, we assumed that there are no unknown cavities inside, and the building material has the properties of an ordinary limestone and is evenly distributed in and out of the pyramid. With these assumptions, we obtained interesting results that can have important practical applications,” says Andrey Evlyukhin, DSc, scientific supervisor and coordinator of the research.
Now the scientists plan to use the results to reproduce similar effects at the nanoscale.
“By choosing a material with suitable electromagnetic properties, we can obtain pyramidal nanoparticles with a potential for practical application in nanosensors and effective solar cells,” says Polina Kapitanova, PhD, associate at the Faculty of Physics and Engineering of ITMO University.
The research was supported by the Russian Science Foundation and the Deutsche Forschungsgemeinschaft (grants № 17-79-20379 and №16-12-10287).
At left, different patterns of slices through a thin metal foil, are made by a focused ion beam. These patterns cause the metal to fold up into predetermined shapes, which can be used for such purposes as modifying a beam of light. Courtesy of the researchers
Nanokiragami (or nano-kiragami) is a fully fledged field of research? That was news to me as was much else in a July 6, 2018 news item on ScienceDaily,
Nanokirigami has taken off as a field of research in the last few years; the approach is based on the ancient arts of origami (making 3-D shapes by folding paper) and kirigami (which allows cutting as well as folding) but applied to flat materials at the nanoscale, measured in billionths of a meter.
Now, researchers at MIT [Massachusetts Institute of Technology] and in China have for the first time applied this approach to the creation of nanodevices to manipulate light, potentially opening up new possibilities for research and, ultimately, the creation of new light-based communications, detection, or computational devices.
The findings are described today [July 6, 2018] in the journal Science Advances, in a paper by MIT professor of mechanical engineering Nicholas X Fang and five others. Using methods based on standard microchip manufacturing technology, Fang and his team used a focused ion beam to make a precise pattern of slits in a metal foil just a few tens of nanometers thick. The process causes the foil to bend and twist itself into a complex three-dimensional shape capable of selectively filtering out light with a particular polarization.
Previous attempts to create functional kirigami devices have used more complicated fabrication methods that require a series of folding steps and have been primarily aimed at mechanical rather than optical functions, Fang says. The new nanodevices, by contrast, can be formed in a single folding step and could be used to perform a number of different optical functions.
For these initial proof-of-concept devices, the team produced a nanomechanical equivalent of specialized dichroic filters that can filter out circularly polarized light that is either “right-handed” or “left-handed.” To do so, they created a pattern just a few hundred nanometers across in the thin metal foil; the result resembles pinwheel blades, with a twist in one direction that selects the corresponding twist of light.
The twisting and bending of the foil happens because of stresses introduced by the same ion beam that slices through the metal. When using ion beams with low dosages, many vacancies are created, and some of the ions end up lodged in the crystal lattice of the metal, pushing the lattice out of shape and creating strong stresses that induce the bending.
“We cut the material with an ion beam instead of scissors, by writing the focused ion beam across this metal sheet with a prescribed pattern,” Fang says. “So you end up with this metal ribbon that is wrinkling up” in the precisely planned pattern.
“It’s a very nice connection of the two fields, mechanics and optics,” Fang says. The team used helical patterns to separate out the clockwise and counterclockwise polarized portions of a light beam, which may represent “a brand new direction” for nanokirigami research, he says.
The technique is straightforward enough that, with the equations the team developed, researchers should now be able to calculate backward from a desired set of optical characteristics and produce the needed pattern of slits and folds to produce just that effect, Fang says.
“It allows a prediction based on optical functionalities” to create patterns that achieve the desired result, he adds. “Previously, people were always trying to cut by intuition” to create kirigami patterns for a particular desired outcome.
The research is still at an early stage, Fang points out, so more research will be needed on possible applications. But these devices are orders of magnitude smaller than conventional counterparts that perform the same optical functions, so these advances could lead to more complex optical chips for sensing, computation, or communications systems or biomedical devices, the team says.
For example, Fang says, devices to measure glucose levels often use measurements of light polarity, because glucose molecules exist in both right- and left-handed forms which interact differently with light. “When you pass light through the solution, you can see the concentration of one version of the molecule, as opposed to the mixture of both,” Fang explains, and this method could allow for much smaller, more efficient detectors.
Circular polarization is also a method used to allow multiple laser beams to travel through a fiber-optic cable without interfering with each other. “People have been looking for such a system for laser optical communications systems” to separate the beams in devices called optical isolaters, Fang says. “We have shown that it’s possible to make them in nanometer sizes.”
The team also included MIT graduate student Huifeng Du; Zhiguang Liu, Jiafang Li (project supervisor), and Ling Lu at the Chinese Academy of Sciences in Beijing; and Zhi-Yuan Li at the South China University of Technology. The work was supported by the National Key R&D Program of China, the National Natural Science Foundation of China, and the U.S Air Force Office of Scientific Research.
Over the past five years, University of Chicago chemist Bozhi Tian has been figuring out how to control biology with light.
A longterm science goal is devices to serve as the interface between researcher and body—both as a way to understand how cells talk among each other and within themselves, and eventually, as a treatment for brain or nervous system disorders [emphasis mine] by stimulating nerves to fire or limbs to move. Silicon—a versatile, biocompatible material used in both solar panels and surgical implants—is a natural choice.
In a paper published April 30 in Nature Biomedical Engineering, Tian’s team laid out a system of design principles for working with silicon to control biology at three levels—from individual organelles inside cells to tissues to entire limbs. The group has demonstrated each in cells or mice models, including the first time anyone has used light to control behavior without genetic modification.
“We want this to serve as a map, where you can decide which problem you would like to study and immediately find the right material and method to address it,” said Tian, an assistant professor in the Department of Chemistry.
Researchers built this thin layer of silicon lace to modulate neural signals when activated by light. Courtesy of Yuanwen Jiang and Bozhi Tian
The scientists’ map lays out best methods to craft silicon devices depending on both the intended task and the scale—ranging from inside a cell to a whole animal.
For example, to affect individual brain cells, silicon can be crafted to respond to light by emitting a tiny ionic current, which encourages neurons to fire. But in order to stimulate limbs, scientists need a system whose signals can travel farther and are stronger—such as a gold-coated silicon material in which light triggers a chemical reaction.
The mechanical properties of the implant are important, too. Say researchers would like to work with a larger piece of the brain, like the cortex, to control motor movement. The brain is a soft, squishy substance, so they’ll need a material that’s similarly soft and flexible, but can bind tightly against the surface. They’d want thin and lacy silicon, say the design principles.
The team favors this method because it doesn’t require genetic modification or a power supply wired in, since the silicon can be fashioned into what are essentially tiny solar panels. (Many other forms of monitoring or interacting with the brain need to have a power supply, and keeping a wire running into a patient is an infection risk.)
They tested the concept in mice and found they could stimulate limb movements by shining light on brain implants. Previous research tested the concept in neurons.
“We don’t have answers to a number of intrinsic questions about biology, such as whether individual mitochondria communicate remotely through bioelectric signals,” said Yuanwen Jiang, the first author on the paper, then a graduate student at UChicago and now a postdoctoral researcher at Stanford. “This set of tools could address such questions as well as pointing the way to potential solutions for nervous system disorders.”
Other UChicago authors were Assoc. Profs. Chin-Tu Chen and Chien-Min Kao, Asst. Prof Xiaoyang, postdoctoral researchers Jaeseok Yi, Yin Fang, Xiang Gao, Jiping Yue, Hsiu-Ming Tsai, Bing Liu and Yin Fang, graduate students Kelliann Koehler, Vishnu Nair, and Edward Sudzilovsky, and undergraduate student George Freyermuth.
Other researchers on the paper hailed from Northwestern University, the University of Illinois at Chicago and Hong Kong Polytechnic University.
The researchers have also made this video illustrating their work,
via Gfycat Tiny silicon nanowires (in blue), activated by light, trigger activity in neurons. (Courtesy Yuanwen Jiang and Bozhi Tian)
Here’s a link to and a citation for the paper,
Rational design of silicon structures for optically controlled multiscale biointerfaces by Yuanwen Jiang, Xiaojian Li, Bing Liu, Jaeseok Yi, Yin Fang, Fengyuan Shi, Xiang Gao, Edward Sudzilovsky, Ramya Parameswaran, Kelliann Koehler, Vishnu Nair, Jiping Yue, KuangHua Guo, Yin Fang, Hsiu-Ming Tsai, George Freyermuth, Raymond C. S. Wong, Chien-Min Kao, Chin-Tu Chen, Alan W. Nicholls, Xiaoyang Wu, Gordon M. G. Shepherd, & Bozhi Tian. Nature Biomedical Engineering (2018) doi:10.1038/s41551-018-0230-1 Published: 30 April 2018
How does the ‘brain’ of a living cell work, allowing an organism to function and thrive in changing and unfavourable environments?
Queensland University of Technology (QUT) researcher Dr Robyn Araujo has developed new mathematics to solve a longstanding mystery of how the incredibly complex biological networks within cells can adapt and reset themselves after exposure to a new stimulus.
Her findings, published in Nature Communications, provide a new level of understanding of cellular communication and cellular ‘cognition’, and have potential application in a variety of areas, including new targeted cancer therapies and drug resistance.
Dr Araujo, a lecturer in applied and computational mathematics in QUT’s Science and Engineering Faculty, said that while we know a great deal about gene sequences, we have had extremely limited insight into how the proteins encoded by these genes work together as an integrated network – until now.
“Proteins form unfathomably complex networks of chemical reactions that allow cells to communicate and to ‘think’ – essentially giving the cell a ‘cognitive’ ability, or a ‘brain’,” she said. “It has been a longstanding mystery in science how this cellular ‘brain’ works.
“We could never hope to measure the full complexity of cellular networks – the networks are simply too large and interconnected and their component proteins are too variable.
“But mathematics provides a tool that allows us to explore how these networks might be constructed in order to perform as they do.
“My research is giving us a new way to look at unravelling network complexity in nature.”
Dr Araujo’s work has focused on the widely observed function called perfect adaptation – the ability of a network to reset itself after it has been exposed to a new stimulus.
“An example of perfect adaptation is our sense of smell,” she said. “When exposed to an odour we will smell it initially but after a while it seems to us that the odour has disappeared, even though the chemical, the stimulus, is still present.
“Our sense of smell has exhibited perfect adaptation. This process allows it to remain sensitive to further changes in our environment so that we can detect both very feint and very strong odours.
“This kind of adaptation is essentially what takes place inside living cells all the time. Cells are exposed to signals – hormones, growth factors, and other chemicals – and their proteins will tend to react and respond initially, but then settle down to pre-stimulus levels of activity even though the stimulus is still there.
“I studied all the possible ways a network can be constructed and found that to be capable of this perfect adaptation in a robust way, a network has to satisfy an extremely rigid set of mathematical principles. There are a surprisingly limited number of ways a network could be constructed to perform perfect adaptation.
“Essentially we are now discovering the needles in the haystack in terms of the network constructions that can actually exist in nature.
“It is early days, but this opens the door to being able to modify cell networks with drugs and do it in a more robust and rigorous way. Cancer therapy is a potential area of application, and insights into how proteins work at a cellular level is key.”
Dr Araujo said the published study was the result of more than “five years of relentless effort to solve this incredibly deep mathematical problem”. She began research in this field while at George Mason University in Virginia in the US.
Her mentor at the university’s College of Science and co-author of the Nature Communications paper, Professor Lance Liotta, said the “amazing and surprising” outcome of Dr Araujo’s study is applicable to any living organism or biochemical network of any size.
“The study is a wonderful example of how mathematics can have a profound impact on society and Dr Araujo’s results will provide a set of completely fresh approaches for scientists in a variety of fields,” he said.
“For example, in strategies to overcome cancer drug resistance – why do tumours frequently adapt and grow back after treatment?
“It could also help understanding of how our hormone system, our immune defences, perfectly adapt to frequent challenges and keep us well, and it has future implications for creating new hypotheses about drug addiction and brain neuron signalling adaptation.”
From a May 11, 2018 United Nations Educational, Scientific and Cultural Organization (UNESCO) press release (received via email),
UNESCO will welcome leading scientists on 16 May 2018 for the 1st edition of the International Day of Light (02:30-08:00 pm) to celebrate the role light plays in our daily lives. Researchers and intellectuals will examine how light-based technologies can contribute to meet pressing challenges in diverse areas, such as medicine, education, agriculture and energy.
UNESCO Director-General Audrey Azoulay will open this event, which will count with the participation of renowned scientists, including:
Kip Thorne, 2017 Nobel Prize in Physics, California Institute of Technology (United States of America).
Claude Cohen-Tannoudji, 1997 Nobel Prize in Physics, Collège de France.
Khaled Toukan, Director of the Synchrotron-light for Experimental Science and Applications in the Middle East (SESAME) based in Allan, Jordan.
The programme of keynotes and roundtables will address many key issues including science policy, our perception of the universe, and international cooperation, through contributions from experts and scientists from around the world.
The programme also includes cultural events, an illumination of UNESCO Headquarters, a photonics science show and an exhibit on the advances of light-based technologies and art.
The debates that flourished in 2015, in the framework of the International Year of Light, highlighted the importance of light sciences and light-based technologies in achieving the United Nations Sustainable Development Goals. Several thousand events were held in 147 countries during the Year placed under the auspices of UNESCO.
The proclamation of 16 May as the International Day of Light was supported by UNESCO’s Executive Board following a proposal by Ghana, Mexico, New Zealand and the Russian Federation, and approved by the UNESCO General Conference in November 2017.
I have taken a look at the programme which is pretty interesting. Unfortunately, I can’t excerpt parts of it for inclusion here as very odd things happen when I attempt to ‘copy and paste’. On the plus side. there’s a bit more information about this ‘new day’ on its event page,
Light plays a central role in our lives. On the most fundamental level, through photosynthesis, light is at the origin of life itself. The study of light has led to promising alternative energy sources, lifesaving medical advances in diagnostics technology and treatments, light-speed internet and many other discoveries that have revolutionized society and shaped our understanding of the universe. These technologies were developed through centuries of fundamental research on the properties of light – starting with Ibn Al-Haytham’s seminal work, Kitab al-Manazir (Book of Optics), published in 1015 and including Einstein’s work at the beginning of the 20th century, which changed the way we think about time and light.
The International Day of Light celebrates the role light plays in science, culture and art, education, and sustainable development, and in fields as diverse as medicine, communications, and energy. The will allow many different sectors of society worldwide to participate in activities that demonstrates how science, technology, art and culture can help achieve the goals of UNESCO – building the foundation for peaceful societies.
The International Day of Light is celebrated on 16 May each year, the anniversary of the first successful operation of the laser in 1960 by physicist and engineer, Theodore Maiman. This day is a call to strengthen scientific cooperation and harness its potential to foster peace and sustainable development.
Happy International Day of Light on Wednesday, May 16, 2018!
Researcher Bor-Kai Hsiung’s work has graced this blog before but the topic was tarantulas and their structural colour. This time, it’s all about Australian peacock spiders and their structural colour according to a December 22, 2017 news item on ScienceDaily,
Even if you are arachnophobic, you probably have seen pictures or videos of Australian peacock spiders (Maratus spp.). These tiny spiders are only 1-5 mm long but are famous for their flamboyant courtship displays featuring diverse and intricate body colorations, patterns, and movements.
The spiders extremely large anterior median eyes have excellent color vision and combine with their bright colors to make peacock spiders cute enough to cure most people of their arachnophobia. But these displays aren’t just pretty to look at, they also inspire new ways for humans to produce color in technology.
One species of peacock spider — the rainbow peacock spider (Maratus robinsoni) is particularly neat, because it showcases an intense rainbow iridescent signal in males’ courtship displays to the females. This is the first known instance in nature of males using an entire rainbow of colors to entice females. Dr. Bor-Kai Hsiung led an international team of researchers from the US (UAkron, Cal Tech, UC San Diego, UNL [University of Nebraska-Lincoln]), Belgium (Ghent University), Netherlands (UGroningen), and Australia to discover how rainbow peacock spiders produce this unique multi-color iridescent signal.
Using a diverse array of research techniques, including light and electron microscopy, hyperspectral imaging, imaging scatterometry, nano 3D printing and optical modeling, the team found the origin of this intense rainbow iridescence emerged from specialized abdominal scales of the spiders. These scales have an airfoil-like microscopic 3D contour with nanoscale diffraction grating structures on the surface.
The interaction between the surface nano-diffraction grating and the microscopic curvature of the scales enables separation and isolation of light into its component wavelengths at finer angles and smaller distances than are possible with current manmade engineering technologies.
Inspiration from these super iridescent scales can be used to overcome current limitations in spectral manipulation, and to further reduce the size of optical spectrometers for applications where fine-scale spectral resolution is required in a very small package, notably instruments on space missions, or wearable chemical detection systems. And it could have a wide array of implications to fields ranging from life sciences and biotechnologies to material sciences and engineering.
Here’s a video of an Australian rainbow peacock spider,
Here’s more from the YouTube description published on April 13, 2017 by Peacockspiderman,
Scenes of Maratus robinsoni, a spider Peter Robinson discovered and David Hill and I named it after him in 2012. You can read our description on pages 36-41 in Peckhamia 103.2, which can be downloaded from the Peckhamia website http://peckhamia.com/peckhamia_number…. This is one of the two smallest species of peacock spider (2.5 mm long) and the only spider we know of in which colour changes occur every time it moves, this video was created to document this. Music: ‘Be Still’ by Johannes Bornlöf licensed through my MCN ‘Brave Bison’ from ‘Epidemic Sound’ For licensing inquiries please contact Brave Bison firstname.lastname@example.org
The University of California at San Diego also published a December 22, 2017 news release about this work, which covers some of the same ground while providing a few new tidbits of information,
Brightly colored Australian peacock spiders (Maratus spp.) captivate even the most arachnophobic viewers with their flamboyant courtship displays featuring diverse and intricate body colorations, patterns, and movements – all packed into miniature bodies measuring less than five millimeters in size for many species. However, these displays are not just pretty to look at. They also inspire new ways for humans to produce color in technology.
One species of peacock spider – the rainbow peacock spider (Maratus robinsoni) – is particularly impressive, because it showcases an intense rainbow iridescent signal in males’ courtship displays to females. This is the first known instance in nature of males using an entire rainbow of colors to entice females to mate. But how do males make their rainbows? A new study published in Nature Communications looked to answer that question.
Figuring out the answers was inherently interdisciplinary so Bor-Kai Hsiung, a postdoctoral scholar at Scripps Institution of Oceanography at the University of California San Diego, assembled an international team that included biologists, physicists and engineers. Starting while he was a Ph.D. student at The University of Akron under the mentorship of Todd Blackledge and Matthew Shawkey, the team included researchers from UA, Scripps Oceanography, California Institute of Technology, and University of Nebraska-Lincoln, the University of Ghent in Belgium, University of Groningen in Netherlands, and Australia to discover how rainbow peacock spiders produce this unique iridescent signal.
The team investigated the spider’s photonic structures using techniques that included light and electron microscopy, hyperspectral imaging, imaging scatterometry and optical modeling to generate hypotheses about how the spider’s scale generate such intense rainbows. The team then used cutting-edge nano 3D printing to fabricate different prototypes to test and validate their hypotheses. In the end, they found that the intense rainbow iridescence emerged from specialized abdominal scales on the spiders. These scales combine an airfoil-like microscopic 3D contour with nanoscale diffraction grating structures on the surface. It is the interaction between the surface nano-diffraction grating and the microscopic curvature of the scales that enables separation and isolation of light into its component wavelengths at finer angles and smaller distances than are possible with current engineering technologies.
“Who knew that such a small critter would create such an intense iridescence using extremely sophisticated mechanisms that will inspire optical engineers,” said Dimitri Deheyn, Hsuing’s advisor at Scripps Oceanography and a coauthor of the study.
For Hsiung, the finding wasn’t quite so unexpected.
“One of the main questions that I wanted to address in my Ph.D. dissertation was ‘how does nature modulate iridescence?’ From a biomimicry perspective, to fully understand and address a question, one has to take extremes from both ends into consideration. I purposefully chose to study these tiny spiders with intense iridescence after having investigated the non-iridescent blue tarantulas,” said Hsiung.
The mechanism behind these tiny rainbows may inspire new color technology, but would not have been discovered without research combining basic natural history with physics and engineering, the researchers said.
“Nanoscale 3D printing allowed us to experimentally validate our models, which was really exciting,” said Shawkey. “We hope that these techniques will become common in the future.”
“As an engineer, what I found fascinating about these spider structural colors is how these long evolved complex structures can still outperform human engineering,” said Radwanul Hasan Siddique, a postdoctoral scholar at Caltech and study coauthor. “Even with high-end fabrication techniques, we could not replicate the exact structures. I wonder how the spiders assemble these fancy structural patterns in the first place!”
Inspiration from these super iridescent spider scales can be used to overcome current limitations in spectral manipulation, and to reduce the size of optical spectrometers for applications where fine-scale spectral resolution is required in a very small package, notably instruments on space missions, or wearable chemical detection systems.
In the end, peacock spiders don’t just produce nature’s smallest rainbows.They could also have implications for a wide array of fields ranging from life sciences and biotechnologies to material sciences and engineering.
Before citing the paper and providing a link, here’s a story by Robert F. Service for Science magazine about attempts to capitalize on ‘spider technology’, in this case spider silk,
The hype over spider silk has been building since 1710. That was the year François Xavier Bon de Saint Hilaire, president of the Royal Society of Sciences in Montpellier, France, wrote to his colleagues, “You will be surpriz’d to hear, that Spiders make a Silk, as beautiful, strong and glossy, as common Silk.” Modern pitches boast that spider silk is five times stronger than steel yet more flexible than rubber. If it could be made into ropes, a macroscale web would be able to snare a jetliner.
The key word is “if.” Researchers first cloned a spider silk gene in 1990, in hopes of incorporating it into other organisms to produce the silk. (Spiders can’t be farmed like silkworms because they are territorial and cannibalistic.) Today, Escherichia coli bacteria, yeasts, plants, silkworms, and even goats have been genetically engineered to churn out spider silk proteins, though the proteins are often shorter and simpler than the spiders’ own. Companies have managed to spin those proteins into enough high-strength thread to produce a few prototype garments, including a running shoe by Adidas and a lightweight parka by The North Face. But so far, companies have struggled to mass produce these supersilks.
Some executives say that may finally be about to change. One Emeryville, California-based startup, Bolt Threads, says it has perfected growing spider silk proteins in yeast and is poised to turn out tons of spider silk thread per year. In Lansing, Michigan, Kraig Biocraft Laboratories says it needs only to finalize negotiations with silkworm farms in Vietnam to produce mass quantities of a combination spider/silkworm silk, which the U.S. Army is now testing for ballistics protection. …
I encourage you to read Service’s article in its entirety if the commercialization prospects for spider silk interest you as it includes gems such as this,
Spider silk proteins are already making their retail debut—but in cosmetics and medical devices, not high-strength fibers. AMSilk grows spider silk proteins in E. coli and dries the purified protein into powders or mixes it into gels, for use as additives for personal care products, such as moisture-retaining skin lotions. The silk proteins supposedly help the lotions form a very smooth, but breathable, layer over the skin. Römer says the company now sells tons of its purified silk protein ingredients every year.
Finally, here’s a citation for and a link to the paper about Australian peacock spiders and nanophotonics,
Rainbow peacock spiders inspire miniature super-iridescent optics by Bor-Kai Hsiung, Radwanul Hasan Siddique, Doekele G. Stavenga, Jürgen C. Otto, Michael C. Allen, Ying Liu, Yong-Feng Lu, Dimitri D. Deheyn, Matthew D. Shawkey, & Todd A. Blackledge. Nature Communications 8, Article number: 2278 (2017) doi:10.1038/s41467-017-02451-x Published online: 22 December 2017
The American Chemical Society (ACS) and the Massachusetts Institute of Technology (MIT) have both issued news releases about the latest in bioluminescence.The researchers tested their work on watercress, a vegetable that was viewed in almost sacred terms in my family; it was not easily available in Vancouver (Canada) when I was child.
My father would hunt down fresh watercress by checking out the Chinese grocery stores. He could spot the fresh stuff from across the street while driving at 30 miles or more per hour. Spotting it entailed an immediate hunt for parking (my father hated to pay so we might have go around the block a few times or more) and a dash out of the car to ensure that he got his watercress before anyone else spotted it. These days it’s much more easily available and, thankfully, my father has passed on so he won’t have to think about glowing watercress.
The 2009 film “Avatar” created a lush imaginary world, illuminated by magical, glowing plants. Now researchers are starting to bring this spellbinding vision to life to help reduce our dependence on artificial lighting. They report in ACS’ journal Nano Letters a way to infuse plants with the luminescence of fireflies.
Nature has produced many bioluminescent organisms, however, plants are not among them. Most attempts so far to create glowing greenery — decorative tobacco plants in particular — have relied on introducing the genes of luminescent bacteria or fireflies through genetic engineering. But getting all the right components to the right locations within the plants has been a challenge. To gain better control over where light-generating ingredients end up, Michael S. Strano and colleagues recently created nanoparticles that travel to specific destinations within plants. Building on this work, the researchers wanted to take the next step and develop a “nanobionic,” glowing plant.
The team infused watercress and other plants with three different nanoparticles in a pressurized bath. The nanoparticles were loaded with light-emitting luciferin; luciferase, which modifies luciferin and makes it glow; and coenzyme A, which boosts luciferase activity. Using size and surface charge to control where the sets of nanoparticles could go within the plant tissues, the researchers could optimize how much light was emitted. Their watercress was half as bright as a commercial 1 microwatt LED and 100,000 times brighter than genetically engineered tobacco plants. Also, the plant could be turned off by adding a compound that blocks luciferase from activating luciferin’s glow.
Imagine that instead of switching on a lamp when it gets dark, you could read by the light of a glowing plant on your desk.
MIT engineers have taken a critical first step toward making that vision a reality. By embedding specialized nanoparticles into the leaves of a watercress plant, they induced the plants to give off dim light for nearly four hours. They believe that, with further optimization, such plants will one day be bright enough to illuminate a workspace.
“The vision is to make a plant that will function as a desk lamp — a lamp that you don’t have to plug in. The light is ultimately powered by the energy metabolism of the plant itself,” says Michael Strano, the Carbon P. Dubbs Professor of Chemical Engineering at MIT and the senior author of the study
This technology could also be used to provide low-intensity indoor lighting, or to transform trees into self-powered streetlights, the researchers say.
MIT postdoc Seon-Yeong Kwak is the lead author of the study, which appears in the journal Nano Letters.
Plant nanobionics, a new research area pioneered by Strano’s lab, aims to give plants novel features by embedding them with different types of nanoparticles. The group’s goal is to engineer plants to take over many of the functions now performed by electrical devices. The researchers have previously designed plants that can detect explosives and communicate that information to a smartphone, as well as plants that can monitor drought conditions.
Lighting, which accounts for about 20 percent of worldwide energy consumption, seemed like a logical next target. “Plants can self-repair, they have their own energy, and they are already adapted to the outdoor environment,” Strano says. “We think this is an idea whose time has come. It’s a perfect problem for plant nanobionics.”
To create their glowing plants, the MIT team turned to luciferase, the enzyme that gives fireflies their glow. Luciferase acts on a molecule called luciferin, causing it to emit light. Another molecule called co-enzyme A helps the process along by removing a reaction byproduct that can inhibit luciferase activity.
The MIT team packaged each of these three components into a different type of nanoparticle carrier. The nanoparticles, which are all made of materials that the U.S. Food and Drug Administration classifies as “generally regarded as safe,” help each component get to the right part of the plant. They also prevent the components from reaching concentrations that could be toxic to the plants.
The researchers used silica nanoparticles about 10 nanometers in diameter to carry luciferase, and they used slightly larger particles of the polymers PLGA and chitosan to carry luciferin and coenzyme A, respectively. To get the particles into plant leaves, the researchers first suspended the particles in a solution. Plants were immersed in the solution and then exposed to high pressure, allowing the particles to enter the leaves through tiny pores called stomata.
Particles releasing luciferin and coenzyme A were designed to accumulate in the extracellular space of the mesophyll, an inner layer of the leaf, while the smaller particles carrying luciferase enter the cells that make up the mesophyll. The PLGA particles gradually release luciferin, which then enters the plant cells, where luciferase performs the chemical reaction that makes luciferin glow.
The researchers’ early efforts at the start of the project yielded plants that could glow for about 45 minutes, which they have since improved to 3.5 hours. The light generated by one 10-centimeter watercress seedling is currently about one-thousandth of the amount needed to read by, but the researchers believe they can boost the light emitted, as well as the duration of light, by further optimizing the concentration and release rates of the components.
Previous efforts to create light-emitting plants have relied on genetically engineering plants to express the gene for luciferase, but this is a laborious process that yields extremely dim light. Those studies were performed on tobacco plants and Arabidopsis thaliana, which are commonly used for plant genetic studies. However, the method developed by Strano’s lab could be used on any type of plant. So far, they have demonstrated it with arugula, kale, and spinach, in addition to watercress.
For future versions of this technology, the researchers hope to develop a way to paint or spray the nanoparticles onto plant leaves, which could make it possible to transform trees and other large plants into light sources.
“Our target is to perform one treatment when the plant is a seedling or a mature plant, and have it last for the lifetime of the plant,” Strano says. “Our work very seriously opens up the doorway to streetlamps that are nothing but treated trees, and to indirect lighting around homes.”
The researchers have also demonstrated that they can turn the light off by adding nanoparticles carrying a luciferase inhibitor. This could enable them to eventually create plants that shut off their light emission in response to environmental conditions such as sunlight, the researchers say.
Here’s a link to and a citation for the paper,
A Nanobionic Light-Emitting Plant by Seon-Yeong Kwak, Juan Pablo Giraldo, Min Hao Wong, Volodymyr B. Koman, Tedrick Thomas Salim Lew, Jon Ell, Mark C. Weidman, Rosalie M. Sinclair, Markita P. Landry, William A. Tisdale, and Michael S. Strano. Nano Lett., 2017, 17 (12), pp 7951–7961 DOI: 10.1021/acs.nanolett.7b04369 Publication Date (Web): November 17, 2017
Memristors – or resistive memory – are nanoelectronic devices that are very promising components for next generation memory and computing devices. They are two-terminal electric elements similar to a conventional resistor – however, the electric resistance in a memristor is dependent on the charge passing through it; which means that its conductance can be precisely modulated by charge or flux through it. Its special property is that its resistance can be programmed (resistor function) and subsequently remains stored (memory function).
In this sense, a memristor is similar to a synapse in the human brain because it exhibits the same switching characteristics, i.e. it is able, with a high level of plasticity, to modify the efficiency of signal transfer between neurons under the influence of the transfer itself. That’s why researchers are hopeful to use memristors for the fabrication of electronic synapses for neuromorphic (i.e. brain-like) computing that mimics some of the aspects of learning and computation in human brains.
Human brains may be slow at pure number crunching but they are excellent at handling fast dynamic sensory information such as image and voice recognition. Walking is something that we take for granted but this is quite challenging for robots, especially over uneven terrain.
“Memristors present an opportunity to make new types of computers that are different from existing von Neumann architectures, which traditional computers are based upon,” Dr Neil T. Kemp, a Lecturer in Physics at the University of Hull [UK], tells Nanowerk. “Our team at the University of Hull is focussed on making memristor devices dynamically reconfigurable and adaptive – we believe this is the route to making a new generation of artificial intelligence systems that are smarter and can exhibit complex behavior. Such systems would also have the advantage of memristors, high density integration and lower power usage, so these systems would be more lightweight, portable and not need re-charging so often – which is something really needed for robots etc.”
In their new paper in Nanoscale (“Reversible Optical Switching Memristors with Tunable STDP Synaptic Plasticity: A Route to Hierarchical Control in Artificial Intelligent Systems”), Kemp and his team demonstrate the ability to reversibly control the learning properties of memristors via optical means.
The reversibility is achieved by changing the polarization of light. The researchers have used this effect to demonstrate tuneable learning in a memristor. One way this is achieved is through something called Spike Timing Dependent Plasticity (STDP), which is an effect known to occur in human brains and is linked with sensory perception, spatial reasoning, language and conscious thought in the neocortex.
STDP learning is based upon differences in the arrival time of signals from two adjacent neurons. The University of Hull team has shown that they can modulate the synaptic plasticity via optical means which enables the devices to have tuneable learning.
“Our research findings are important because it demonstrates that light can be used to control the learning properties of a memristor,” Kemp points out. “We have shown that light can be used in a reversible manner to change the connection strength (or conductivity) of artificial memristor synapses and as well control their ability to forget i.e. we can dynamically change device to have short-term or long-term memory.”
According to the team, there are many potential applications, such as adaptive electronic circuits controllable via light, or in more complex systems, such as neuromorphic computing, the development of optically reconfigurable neural networks.
Having optically controllable memristors can also facilitate the implementation of hierarchical control in larger artificial-brain like systems, whereby some of the key processes that are carried out by biological molecules in human brains can be emulated in solid-state devices through patterning with light.
Some of these processes include synaptic pruning, conversion of short term memory to long term memory, erasing of certain memories that are no longer needed or changing the sensitivity of synapses to be more adept at learning new information.
“The ability to control this dynamically, both spatially and temporally, is particularly interesting since it would allow neural networks to be reconfigurable on the fly through either spatial patterning or by adjusting the intensity of the light source,” notes Kemp.
In their new paper in Nanoscale Currently, the devices are more suited to neuromorphic computing applications, which do not need to be as fast. Optical control of memristors opens the route to dynamically tuneable and reprogrammable synaptic circuits as well the ability (via optical patterning) to have hierarchical control in larger and more complex artificial intelligent systems.
“Artificial Intelligence is really starting to come on strong in many areas, especially in the areas of voice/image recognition and autonomous systems – we could even say that this is the next revolution, similarly to what the industrial revolution was to farming and production processes,” concludes Kemp. “There are many challenges to overcome though. …
That excerpt should give you the gist of Berger’s article and, for those who need more information, there’s Berger’s article and, also, a link to and a citation for the paper,
It would seem machine learning could experience a significant upgrade if the work in Wei Lu’s University of Michigan laboratory can be scaled for general use. From a December 22, 2017 news item on ScienceDaily,
A new type of neural network made with memristors can dramatically improve the efficiency of teaching machines to think like humans.
The network, called a reservoir computing system, could predict words before they are said during conversation, and help predict future outcomes based on the present.
The research team that created the reservoir computing system, led by Wei Lu, professor of electrical engineering and computer science at the University of Michigan, recently published their work in Nature Communications.
Reservoir computing systems, which improve on a typical neural network’s capacity and reduce the required training time, have been created in the past with larger optical components. However, the U-M group created their system using memristors, which require less space and can be integrated more easily into existing silicon-based electronics.
Memristors are a special type of resistive device that can both perform logic and store data. This contrasts with typical computer systems, where processors perform logic separate from memory modules. In this study, Lu’s team used a special memristor that memorizes events only in the near history.
Inspired by brains, neural networks are composed of neurons, or nodes, and synapses, the connections between nodes.
To train a neural network for a task, a neural network takes in a large set of questions and the answers to those questions. In this process of what’s called supervised learning, the connections between nodes are weighted more heavily or lightly to minimize the amount of error in achieving the correct answer.
Once trained, a neural network can then be tested without knowing the answer. For example, a system can process a new photo and correctly identify a human face, because it has learned the features of human faces from other photos in its training set.
“A lot of times, it takes days or months to train a network,” says Lu. “It is very expensive.”
Image recognition is also a relatively simple problem, as it doesn’t require any information apart from a static image. More complex tasks, such as speech recognition, can depend highly on context and require neural networks to have knowledge of what has just occurred, or what has just been said.
“When transcribing speech to text or translating languages, a word’s meaning and even pronunciation will differ depending on the previous syllables,” says Lu.
This requires a recurrent neural network, which incorporates loops within the network that give the network a memory effect. However, training these recurrent neural networks is especially expensive, Lu says.
Reservoir computing systems built with memristors, however, can skip most of the expensive training process and still provide the network the capability to remember. This is because the most critical component of the system – the reservoir – does not require training.
When a set of data is inputted into the reservoir, the reservoir identifies important time-related features of the data, and hands it off in a simpler format to a second network. This second network then only needs training like simpler neural networks, changing weights of the features and outputs that the first network passed on until it achieves an acceptable level of error.
IMAGE: Schematic of a reservoir computing system, showing the reservoir with internal dynamics and the simpler output. Only the simpler output needs to be trained, allowing for quicker and lower-cost training. Courtesy Wei Lu.
“The beauty of reservoir computing is that while we design it, we don’t have to train it,” says Lu.
The team proved the reservoir computing concept using a test of handwriting recognition, a common benchmark among neural networks. Numerals were broken up into rows of pixels, and fed into the computer with voltages like Morse code, with zero volts for a dark pixel and a little over one volt for a white pixel.
Using only 88 memristors as nodes to identify handwritten versions of numerals, compared to a conventional network that would require thousands of nodes for the task, the reservoir achieved 91% accuracy.
Reservoir computing systems are especially adept at handling data that varies with time, like a stream of data or words, or a function depending on past results.
To demonstrate this, the team tested a complex function that depended on multiple past results, which is common in engineering fields. The reservoir computing system was able to model the complex function with minimal error.
Lu plans on exploring two future paths with this research: speech recognition and predictive analysis.
“We can make predictions on natural spoken language, so you don’t even have to say the full word,” explains Lu.
“We could actually predict what you plan to say next.”
In predictive analysis, Lu hopes to use the system to take in signals with noise, like static from far-off radio stations, and produce a cleaner stream of data. “It could also predict and generate an output signal even if the input stopped,” he says.
IMAGE: Wei Lu, Professor of Electrical Engineering & Computer Science at the University of Michigan holds a memristor he created. Photo: Marcin Szczepanski.
The work was published in Nature Communications in the article, “Reservoir computing using dynamic memristors for temporal information processing”, with authors Chao Du, Fuxi Cai, Mohammed Zidan, Wen Ma, Seung Hwan Lee, and Prof. Wei Lu.
The research is part of a $6.9 million DARPA [US Defense Advanced Research Projects Agency] project, called “Sparse Adaptive Local Learning for Sensing and Analytics [also known as SALLSA],” that aims to build a computer chip based on self-organizing, adaptive neural networks. The memristor networks are fabricated at Michigan’s Lurie Nanofabrication Facility.
Lu and his team previously used memristors in implementing “sparse coding,” which used a 32-by-32 array of memristors to efficiently analyze and recreate images.
Cotton that’s grown with molecules that endow appealing properties – like fluorescence or magnetism – may one day eliminate the need for applying chemical treatments to fabrics to achieve such qualities, a new study suggests. Applying synthetic polymers to fabrics can result in a range of appealing properties, but anything added to a fabric can get washed or worn away. Furthermore, while many fibers used in fabrics are synthetic (e.g., polyester), some consumers prefer natural fibers to avoid issues related to sensation, skin irritation, smoothness, and weight. Here, Filipe Natalio and colleagues created cotton fibers that incorporate composites with fluorescent and magnetic properties. They synthesized glucose derivatives that deliver the desirable molecules into the growing ovules of the cotton plant, Gossypium hirsutum. Thus, the molecules are embedded into the cotton fibers themselves, rather than added in the form of a chemical treatment. The resulting fibers exhibited fluorescent or magnetic properties, respectively, although they were weaker than raw fibers lacking the embedded composites, the authors report. They propose that similar techniques could be expanded to other biological systems such as bacteria, bamboo, silk, and flax – essentially opening a new era of “material farming.”
Robert Service’s Sept. 14, 2017 article for Science explores the potential of growing cotton with new properties (Note: A link has been removed),
You may have heard about smartphones and smart homes. But scientists are also designing smart clothes, textiles that can harvest energy, light up, detect pollution, and even communicate with the internet. The problem? Even when they work, these often chemically treated fabrics wear out rapidly over time. Now, researchers have figured out a way to “grow” some of these functions directly into cotton fibers. If the work holds, it could lead to stronger, lighter, and brighter textiles that don’t wear out.
Yet, as the new paper went to press today in Science, editors at the journal were made aware of mistakes in a figure in the supplemental material that prompted them to issue an Editorial Expression of Concern, at least until they receive clarification from the authors. Filipe Natalio, lead author and chemist at the Weizmann Institute of Science in Rehovot, Israel, says the mistakes were errors in the names of pigments used in control experiments, which he is working with the editors to fix.
That hasn’t dampened enthusiasm for the work. “I like this paper a lot,” says Michael Strano, a chemical engineer at the Massachusetts Institute of Technology in Cambridge. The study, he says, lays out a new way to add new functions into plants without changing their genes through genetic engineering. Those approaches face steep regulatory hurdles for widespread use. “Assuming the methods claimed are correct, that’s a big advantage,” Strano says.
Sam Lemonick’s Sept. 14, 2017 article for forbes.com describes how the researchers introduced new properties (in this case, glowing colours) into the cotton plants,
His [Filipe Natalio] team of researchers in Israel, Germany, and Austria used sugar molecules to sneak new properties into cotton. Like a Trojan horse, Natalio says. They tested the method by tagging glucose with a fluorescent dye molecule that glows green when hit with the right kind of light.
They bathed cotton ovules—the part of the plant that makes the fibers—in the glucose. And just like flowers suck up dyed water in grade school experiments, the ovules absorbed the sugar solution and piped the tagged glucose molecules to their cells. As the fibers grew, they took on a yellowish tinge—and glowed bright green under ultraviolet light.
Glowing cotton wasn’t enough for Natalio. It took his group about six months to be sure they were actually delivering the fluorescent protein into the cotton cells and not just coating the fibers in it. Once they were certain, they decided to push the envelope with something very unnatural: magnets.
This time, Natalio’s team modified glucose with the rare earth metal dysprosium, making a molecule that acts like a magnet. And just like they did with the dye, the researchers fed it to cotton ovules and ended up with fibers with magnetic properties.
Both Service and Lemonwick note that the editor of the journal Science (where the research paper was published) Jeremy Berg has written an expression of editorial concern as of Sept. 14, 2017,
In the 15 September  issue, Science published the Report “Biological fabrication of cellulose fibers with tailored properties” by F. Natalio et al. (1). After the issue went to press, we became aware of errors in the labeling and/or identification of the pigments used for the control experiments detailed in figs. S1 and S2 of the supplementary materials. Science is publishing this Editorial Expression of Concern to alert our readers to this information as we await full explanation and clarification from the authors.
The problem seems to be one of terminology (from the Lemonwick article),
… Filipe Natalio, lead author and chemist at the Weizmann Institute of Science in Rehovot, Israel, says the mistakes were errors in the names of pigments used in control experiments, which he is working with the editors to fix.
These things happen. Terminology and spelling aren’t always the same from one country to the next and it can result in confusion. I’m glad to see the discussion is being held openly.
For the first time, researchers have sent a quantum-secured message containing more than one bit of information per photon through the air above a city. The demonstration showed that it could one day be practical to use high-capacity, free-space quantum communication to create a highly secure link between ground-based networks and satellites, a requirement for creating a global quantum encryption network.
Quantum encryption uses photons to encode information in the form of quantum bits. In its simplest form, known as 2D encryption, each photon encodes one bit: either a one or a zero. Scientists have shown that a single photon can encode even more information—a concept known as high-dimensional quantum encryption—but until now this has never been demonstrated with free-space optical communication in real-world conditions. With eight bits necessary to encode just one letter, for example, packing more information into each photon would significantly speed up data transmission.
This looks like donuts on a stick to me,
For the first time, researchers have demonstrated sending messages in a secure manner using high dimensional quantum cryptography in realistic city conditions. Image Credit: SQO team, University of Ottawa.
An Aug. 24, 2017 Optical Society news release (also on EurekAlert), which originated the news item, describes the work done by a team in Ottawa, Canada, (Note: The ‘Congratulate China’ piece (August 22, 2017 posting) includes excerpts from an article that gave a brief survey of various national teams [including Canada] working on quantum communication networks; Links have been removed),
“Our work is the first to send messages in a secure manner using high-dimensional quantum encryption in realistic city conditions, including turbulence,” said research team lead, Ebrahim Karimi, University of Ottawa, Canada. “The secure, free-space communication scheme we demonstrated could potentially link Earth with satellites, securely connect places where it is too expensive to install fiber, or be used for encrypted communication with a moving object, such as an airplane.”
For the first time, researchers have demonstrated sending messages in a secure manner using high dimensional quantum cryptography in realistic city conditions. Image Credit: SQO team, University of Ottawa.
As detailed in Optica, The Optical Society’s journal for high impact research, the researchers demonstrated 4D quantum encryption over a free-space optical network spanning two buildings 0.3 kilometers apart at the University of Ottawa. This high-dimensional encryption scheme is referred to as 4D because each photon encodes two bits of information, which provides the four possibilities of 01, 10, 00 or 11.
In addition to sending more information per photon, high-dimensional quantum encryption can also tolerate more signal-obscuring noise before the transmission becomes unsecure. Noise can arise from turbulent air, failed electronics, detectors that don’t work properly and from attempts to intercept the data. “This higher noise threshold means that when 2D quantum encryption fails, you can try to implement 4D because it, in principle, is more secure and more noise resistant,” said Karimi.
Using light for encryption
Today, mathematical algorithms are used to encrypt text messages, banking transactions and health information. Intercepting these encrypted messages requires figuring out the exact algorithm used to encrypt a given piece of data, a feat that is difficult now but that is expected to become easier in the next decade or so as computers become more powerful.
Given the expectation that current algorithms may not work as well in the future, more attention is being given to stronger encryption techniques such as quantum key distribution, which uses properties of light particles known as quantum states to encode and send the key needed to decrypt encoded data.
Although wired and free-space quantum encryption has been deployed on some small, local networks, implementing it globally will require sending encrypted messages between ground-based stations and the satellite-based quantum communication networks that would link cities and countries. Horizontal tests through the air can be used to simulate sending signals to satellites, with about three horizontal kilometers being roughly equal to sending the signal through the Earth’s atmosphere to a satellite.
Before trying a three-kilometer test, the researchers wanted to see if it was even possible to perform 4D quantum encryption outside. This was thought to be so challenging that some other scientists in the field said that the experiment would not work. One of the primary problems faced during any free-space experiment is dealing with air turbulence, which distorts the optical signal.
For the tests, the researchers brought their laboratory optical setups to two different rooftops and covered them with wooden boxes to provide some protection from the elements. After much trial and error, they successfully sent messages secured with 4D quantum encryption over their intracity link. The messages exhibited an error rate of 11 percent, below the 19 percent threshold needed to maintain a secure connection. They also compared 4D encryption with 2D, finding that, after error correction, they could transmit 1.6 times more information per photon with 4D quantum encryption, even with turbulence.
“After bringing equipment that would normally be used in a clean, isolated lab environment to a rooftop that is exposed to the elements and has no vibration isolation, it was very rewarding to see results showing that we could transmit secure data,” said Alicia Sit, an undergraduate student in Karimi’s lab.
As a next step, the researchers are planning to implement their scheme into a network that includes three links that are about 5.6 kilometers apart and that uses a technology known as adaptive optics to compensate for the turbulence. Eventually, they want to link this network to one that exists now in the city. “Our long-term goal is to implement a quantum communication network with multiple links but using more than four dimensions while trying to get around the turbulence,” said Sit.
Here’s a link to and a citation for the paper,
High-dimensional intracity quantum cryptography with structured photons by Alicia Sit, Frédéric Bouchard, Robert Fickler, Jérémie Gagnon-Bischoff, Hugo Larocque, Khabat Heshami, Dominique Elser, Christian Peuntinger, Kevin Günthner, Bettina Heim, Christoph Marquardt, Gerd Leuchs, Robert W. Boyd, and Ebrahim Karimi. Optica Vol. 4, Issue 9, pp. 1006-1010 (2017) •https://doi.org/10.1364/OPTICA.4.001006