Scientists at Sandia National Laboratories and the Max Planck Institute for the Science of Light have reported on a device that could replace a roomful of equipment to link photons in a bizarre quantum effect called entanglement. This device — a kind of nano-engineered material called a metasurface — paves the way for entangling photons in complex ways that have not been possible with compact technologies.

When scientists say photons are entangled, they mean they are linked in such a way that actions on one affect the other, no matter where or how far apart the photons are in the universe. It is an effect of quantum mechanics, the laws of physics that govern particles and other very tiny things.

Although the phenomenon might seem odd, scientists have harnessed it to process information in new ways. For example, entanglement helps protect delicate quantum information and correct errors in quantum computing, a field that could someday have sweeping impacts in national security, science and finance. Entanglement is also enabling new, advanced encryption methods for secure communication.

Research for the groundbreaking device, which is a hundred times thinner than a sheet of paper, was performed, in part, at the Center for Integrated Nanotechnologies, a Department of Energy Office of Science user facility operated by Sandia and Los Alamos national laboratories. Sandia’s team received funding from the Office of Science, Basic Energy Sciences program.

Light goes in, entangled photons come out

The new metasurface acts as a doorway to this unusual quantum phenomenon. In some ways, it’s like the mirror in Lewis Carrol’s “Through the Looking-Glass,” through which the young protagonist Alice experiences a strange, new world.

Instead of walking through their new device, scientists shine a laser through it. The beam of light passes through an ultrathin sample of glass covered in nanoscale structures made of a common semiconductor material called gallium arsenide.

“It scrambles all the optical fields,” said Sandia senior scientist Igal Brener, an expert in a field called nonlinear optics who led the Sandia team. Occasionally, he said, a pair of entangled photons at different wavelengths emerge from the sample in the same direction as the incoming laser beam.

Brener said he is excited about this device because it is designed to produce complex webs of entangled photons — not just one pair at a time, but several pairs all entangled together, and some that can be indistinguishable from each other. Some technologies need these complex varieties of so-called multi-entanglement for sophisticated information processing schemes.

Other miniature technologies based on silicon photonics can also entangle photons but without the much-needed level of complex, multi-entanglement. Until now, the only way to produce such results was with multiple tables full of lasers, specialized crystals and other optical equipment.

“It is quite complicated and kind of intractable when this multi-entanglement needs more than two or three pairs,” Brener said. “These nonlinear metasurfaces essentially achieve this task in one sample when before it would have required incredibly complex optical setups.”

The Science paper outlines how the team successfully tuned their metasurface to produce entangled photons with varying wavelengths, a critical precursor to generating several pairs of intricately entangled photons simultaneously.

However, the researchers note in their paper that the efficiency of their device — the rate at which they can generate groups of entangled photons — is lower than that of other techniques and needs to be improved.

What is a metasurface?

A metasurface is a synthetic material that interacts with light and other electromagnetic waves in ways conventional materials can’t. Commercial industries, said Brener, are busy developing metasurfaces because they take up less space and can do more with light than, for instance, a traditional lens.

“You now can replace lenses and thick optical elements with metasurfaces,” Brener said. “Those types of metasurfaces will revolutionize consumer products.”

Sandia is one of the leading institutions in the world performing research in metasurfaces and metamaterials. Between its Microsystems Engineering, Science and Applications complex, which manufactures compound semiconductors, and the nearby Center for Integrated Nanotechnologies, researchers have access to all the specialized tools they need to design, fabricate and analyze these ambitious new materials.

“The work was challenging as it required precise nanofabrication technology to obtain the sharp, narrowband optical resonances that seeds the quantum process of the work,” said Sylvain Gennaro, a former postdoctoral researcher at Sandia who worked on several aspects of the project.

The device was designed, fabricated and tested through a partnership between Sandia and a research group led by physicist Maria Chekhova, an expert in the quantum entanglement of photons at the Max Planck Institute for the Science of Light.

“Metasurfaces are leading to a paradigm shift in quantum optics, combining ultrasmall sources of quantum light with far reaching possibilities for quantum state engineering,” said Tomás Santiago-Cruz, a member of the Max Plank team and first author on the paper.

Brener, who has studied metamaterials for more than a decade, said this newest research could possibly spark a second revolution — one that sees these materials developed not just as a new kind of lens, but as a technology for quantum information processing and other new applications.

“There was one wave with metasurfaces that is already well established and on its way. Maybe there is a second wave of innovative applications coming,” he said

Sandia National Laboratories is a multimission laboratory operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration. Sandia Labs has major research and development responsibilities in nuclear deterrence, global security, defense, energy technologies and economic competitiveness, with main facilities in Albuquerque, New Mexico, and Livermore, California.

People with diabetes may experience damage to the small blood vessels in various organs. The reasons for this are unclear, but it has been known since the 1990s that good control of blood sugar levels reduces the risk of complications. It has, however, not been clear what level of long-term sugar, HbA_1c, people with type 1 diabetes should have in order to avoid serious damage to blood vessels in the eyes and kidneys.

“Our study determines accurately the levels of long-term sugar that can avoid complications. This knowledge can increase a person’s motivation to keep their blood sugar level under control,” says Hans Arnqvist, professor emeritus at Linköping University and leader of the study.

Researchers in the current study, known as VISS (Vascular Diabetic Complications in Southeast Sweden), have followed all children and adults younger than 35 years who developed type 1 diabetes during the period 1983-1987, and who received care in the South-East Healthcare Region of Sweden. All 447 newly diagnosed persons in the region during this period were included in the study. The researchers have followed the patients’ HbA_1c values, which reflect their average blood sugar levels during a longer period. They have also monitored the development of eye- and kidney damage in these patients for a period of between 32 and 36 years after diagnosis.

The small blood vessels in the eye are particularly susceptible to damage in type 1 diabetes. Nearly all patients experience small haemorrhages in the eye that do not affect their vision. In some cases, new blood vessels develop in the retina. The latter is known as ‘proliferative retinopathy’, and can lead to blindness. Another effect of diabetes concerns the area known as the ‘macula’ of the retina, where high-focus vision is located. Damage here leads to blurred vision.

The kidneys are not as sensitive to high blood sugar levels as the eye, but the important small blood vessels here can also be damaged. One consequence of such damage is the excretion of blood proteins in the urine. Albumin is the protein with highest concentration in the blood, and when it is present in the urine the condition is known as ‘albuminuria’. The damage to the kidneys eventually leads to impaired kidney function and, in serious cases, kidney failure. This is a fatal condition if untreated, and the patient must either undergo dialysis or receive a kidney transplant.

The blood sugar level in a healthy person is very closely controlled, with a maximum HbA_1c level of 42 mmol/mol (6.0%).

“The results of our study show that people with type 1 diabetes for at least 32 years should keep their mean long-term sugar level below 53 mmol/mol (7.0%), if they are to completely avoid serious damage. The risk of eye- and kidney complications increases as the level increases. Our conclusions relate to avoiding complications arising from blood vessel damage. But if a patient has problems with low blood sugar, hypoglycaemia, it’s not possible to control the blood sugar level so strictly,” says Hans Arnqvist.

The target level for HbA_1c that is suggested by the results of the VISS study agrees with the individual targets recommended by the American Diabetes Association. In Sweden, target levels are given for groups, rather than individuals.

The previous follow-up by the research group was conducted 20 years after the onset of disease. Now after 30 years, the results show that damage has arisen at lower blood sugar levels than was the case after 20 years. More patients have experienced damage, despite having blood sugar levels that are not higher than those they have previously had. In other words, it seems that the threshold for developing complications falls gradually with time. This means that the study does not allow any conclusions for the recommended blood sugar levels of people with type 1 diabetes longer than 30 years after diagnosis.

The VISS study has received funding from the Swedish Child Diabetes Foundation and the Foundation Funds of Region Östergötland.

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Materials provided by Linköping University. Original written by Karin Söderlund Leifler. Note: Content may be edited for style and length.

“When I first saw a video of the cockatoos opening the bins I thought it was such an interesting and unique behavior and I knew we needed to look into it,” says lead author Barbara Klump, a behavioral ecologist at the Max Planck Institute of Animal Behavior.

The cockatoos’ motivation is food waste. “They really like bread,” she says. “Once one gets a bin open all the cockatoos in the vicinity will come and try to get something nice to eat.”

The birds typically pry the bins open with their beaks and then maneuver themselves onto a small rim and flip the lid open. It’s a community affair. “We could actually show that this is a cultural trait,” says Klump. “The cockatoos learn the behavior from observing other cockatoos and within each group they sort of have their own special technique, so across a wide geographic range the techniques are more dissimilar.”

Human residents trying to keep the cockatoos out can’t simply secure the bin lids completely closed because the lids need to open when tipped by an automated arm on the garbage truck. A survey given by the researchers found that people put bricks and stones on their bin lids, strap water bottles to the top, rig ropes to prevent the lid from flipping, use sticks to block the hinges, and switch tactics once the cockatoos figure them out. “There are even commercially available cockatoo locks for bins,” says Klump.

“It’s not just a social learning on the cockatoo side, but it’s also social learning on the human side,” she says. “People come up with new protection methods on their own, but a lot of people actually learn it from their neighbors or people on their street, so they get their inspiration from someone else.”

Klump won’t say who she expects to win the race for control of the bins, but she and her colleagues plan to look at how the cockatoos’ behavior varies from season to season.

Klump expects we will see more of these kinds of human-wildlife interactions in the future. “As cities expand, we will have more interactions with wildlife,” she says. “I’m hoping that there will be a better understanding and more tolerance for the animals that we share our lives with.”

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Materials provided by Cell Press. Note: Content may be edited for style and length.