A thin device causes one of the strangest and most useful phenomena of quantum mechanics — ScienceDaily

An ultra-thin invention could make future computing, sensing and encryption technologies incredibly smaller and more powerful by helping scientists control a strange but useful phenomenon of quantum mechanics, according to a new study by recently published in the journal. science.

Scientists at Sandia National Laboratories and the Max Planck Institute for the Science of Light have reported on a device that can replace a room full of devices to bind photons in a strange quantum effect called entanglement. This device — a type 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 that photons are entangled, they mean that 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 small things.

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

Research on the innovative device, which is a hundred times thinner than a sheet of paper, was conducted in part at the Center for Integrated Nanotechnologies, a user facility of the Department of Energy, Office of Science, operated by Sandia and Los Alamos National Laboratories. The Sandia team received funding from the Office of Science, Basic Energy Sciences program.

Light in, entangled photons out

The new metasurface acts as a gateway to this unusual quantum phenomenon. In a way, it is like the mirror in Lewis Carroll’s Through the Looking-Glass, through which the young protagonist Alice experiences a strange new world.

Instead of walking through their new device, the scientists shine a laser through it. The light beam passes through an ultra-thin glass sample covered in nano-scale structures made of a common semiconductor material called gallium arsenide.

“It crosses all 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 exits the sample in the same direction as the incoming laser beam.

Brener said he’s excited about the device because it’s designed to produce complex networks of entangled photons — not just one pair at a time, but several pairs entangled all together, and some that can be indistinguishable from each other. next. Some technologies need these complex types of so-called multiple interleaving for sophisticated information processing schemes.

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

“It’s quite complicated and somewhat difficult when this multiple interplay needs more than two or three pairs,” Brener said. “These nonlinear metasurfaces essentially accomplish this task in a single sample when it would previously require incredibly complex optical setups.”

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

However, the researchers note in their paper that the efficiency of their device—the rate at which they can generate entangled photon arrays—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 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 conducting research in metasurfaces and metamaterials. Between its Microsystems Engineering, Science and Applications complex, which produces 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 materials. ambitious new.

“The work was challenging as it required precise nanofabrication technology to obtain the sharp, narrow-band optical resonances that carry the quantum work process,” said Sylvain Gennaro, a former Sandia postdoctoral researcher 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 quantum photon entanglement at the Max Planck Institute for the Science of Light.

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

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

“There was a wave of metasurfaces that is already well established and on its way. Perhaps a second wave of innovative applications will come,” 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 US Department of Energy. Sandia Labs has major research and development responsibilities in nuclear deterrence, global security, defense, energy technologies and economic competitiveness, with major facilities in Albuquerque, New Mexico and Livermore, California.

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