A super-thin invention could make future computing, sensing and encryption technologies remarkably smaller and more powerful by helping scientists control a strange but useful phenomenon of quantum mechanics, according to new research recently published in the journal Science.
Scientists from Sandia National Laboratories and the Max Planck Institute for Light Science have reported a device that could replace a room full of equipment to bind 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 and how far apart the photons are in the universe. It’s an effect of quantum mechanics, the laws of physics that govern particles and other tiny things.
Although the phenomenon may seem strange, scientists have exploited it to process information in new ways. For example, entanglement helps protect delicate quantum information and correct errors in quantum computing, an area that could one day have far-reaching implications for national security, science, and finance. The tangle also enables new advanced encryption methods for secure communication.
Research for the breakthrough device, which is a hundred times thinner than a sheet of paper, was carried out, in part, at the Center for Integrated Nanotechnologies, a Department of Energy Office of Science user facility operated by Sandia National Laboratories and Los Alamos. Sandia’s team received funding from the Office of Science, Basic Energy Sciences program.
Light goes in, entangled photons go out
The new metasurface acts as a gateway to this unusual quantum phenomenon. In a way, 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 scanning their new device, the scientists pass a laser through it. The beam of light passes through an ultra-thin glass sample coated with nanoscale structures made of a common semiconductor material called gallium arsenide.
“It blurs all optical fields,” said Sandia lead scientist Igal Brener, an expert in a field called nonlinear optics who led Sandia’s team. Sometimes, he says, a pair of entangled photons at different wavelengths emerge from the sample in the same direction as the incoming laser beam.
Brener said he was excited about the device because it’s designed to produce complex arrays of entangled photons — not just one pair at a time, but multiple pairs all entangled, and some that may be indistinguishable from each other. Some technologies need these complex varieties of so-called multi-entanglements for sophisticated information processing schemes.
Other miniature technologies based on silicon photonics can also entangle photons, but without the necessary level of complex multi-entanglement. Until now, the only way to produce such results was through multiple tables filled with lasers, specialized crystals, and other optical equipment.
“It’s quite complicated and a bit intractable when this multi-tangle requires more than two or three pairs,” Brener said. “These nonlinear metasurfaces essentially achieve this task in a single sample when previously this would have required incredibly complex optical setups. »
The scientific paper describes how the team successfully tuned its metasurface to produce entangled photons with varying wavelengths, an essential precursor to simultaneously generating multiple pairs of intricately entangled photons.
However, the researchers note in their paper that the efficiency of their device – the speed at which they can generate groups of entangled photons – is lower than other techniques and needs improvement.
What is a metasurface?
A metasurface is a synthetic material that interacts with light and other electromagnetic waves in ways that conventional materials cannot. Commercial industries, Brener said, are busy developing metasurfaces because they take up less space and can do more with light than, say, a traditional lens.
“Now you can replace lenses and thick optical elements with metasurfaces,” Brener said. “These types of metasurfaces will revolutionize consumer products. »
Sandia is one of the world’s leading institutions researching metasurfaces and metamaterials. Between its Microsystems Engineering, Science and Applications complex, which manufactures compound semiconductors, and the nearby Center for Integrated Nanotechnology, researchers have access to all the specialized tools they need to design, fabricate and analyze these ambitious new materials. .
“The work was challenging because it required precise nanofabrication technology to achieve the sharp, narrow-band optical resonances that initiate the quantum process of work,” said Sylvain Gennaro, a former postdoctoral researcher at Sandia who worked on several aspects of the project.
The device was designed, manufactured and tested through a partnership between Sandia and a research group led by physicist Maria Chekhova, an expert in quantum photon entanglement at the Max Planck Institute for Light Science.
“Metasurfaces lead to a paradigm shift in quantum optics, combining ultrasmall sources of quantum light with expanded possibilities for quantum state engineering,” said Max team member Tomás Santiago-Cruz. Plank and first author of the article.
Brener, who has studied metamaterials for more than a decade, said this new research could eventually spark a second revolution – one that sees these materials developed not just as a new type of lens, but as a technology for the treatment of quantum information and other new applications.
“There has been a wave of metasurfaces that is already well established and on the way. Maybe there’s a second wave of innovative apps coming,” he said.
Sandia National Laboratories is a multi-mission laboratory operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc., for the National Nuclear Security Administration of the United States Department of Energy. Sandia Labs has significant research and development responsibilities in the areas of nuclear deterrence, global security, defense, energy technologies, and economic competitiveness, with primary facilities in Albuquerque, New Mexico, and in Livermore, California.