This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: There's a new lighthouse on Long Island. But instead of shining light to guide ships through waterways, this one transmits and receives particles of light that carry quantum information.
Perched atop a seven-story building at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory, the "Quantum Lighthouse" is a key pillar of the free-space optical (FSO) link spanning Brookhaven Lab, the State University of New York at Stony Brook (Stony Brook University) and Yale University. "An FSO link is analogous to the wireless technology that allowed today's classical internet to expand beyond wired connections to orbiting satellites, as well as our cellphones," said Justine Haupt, Brookhaven Lab's lead scientist on the cross-institutional FSO link project.
"It's one of the key technologies needed to make a quantum internet truly useful." This FSO link—the first permanent one of its kind—adds a wireless component to the nation's longest quantum network, which spans 161 miles (259 kilometers) across Long Island and the New York metropolitan area. Through this network, researchers transmit entangled photons—pairs of light particles that are intrinsically linked by the laws of quantum mechanics, even when separated by long distances. As a result, measuring one photon instantly reveals information about its counterpart, a unique property that could one day enable ultrasecure communications, advanced quantum sensing and networked quantum computing.
With the FSO link incorporated into the network, researchers can now send entangled photons 13 miles (21 kilometers) through the air between Brookhaven's Quantum Lighthouse in Upton, New York, and Stony Brook University's Quantum Watchtower in Stony Brook, New York. Soon, a third identical facility at Yale in New Haven, Connecticut, will begin operations, enabling researchers to also send entangled photons 30 miles (48 kilometers) across the Long Island Sound. "We are moving past the era of developing quantum devices in the laboratory and entering an age where we actively engineer large quantum systems, such as our long-distance quantum network," said Eden Figueroa, director of Stony Brook's Quantum Institute, endowed presidential professor of physics in the Department of Physics and Astronomy in the College of Arts and Sciences, and a joint appointee at Brookhaven Lab.
"By bridging our labs with deployed fiber and free-space optical quantum links, we are building Einstein's 'spooky action at a distance' thought experiments, while also establishing secure quantum networks and training the brilliant minds who will run them." Researchers generate entangled photons at network nodes, like Brookhaven's Quantum Information Science & Technology (QIST) Laboratory, by shining a laser into a specially designed crystal or optical device. This splits one photon into an entangled pair that can then be separated and transmitted through commercial cable to other network nodes. But once these particles reach FSO link nodes, like the Quantum Lighthouse, researchers can no longer rely on cable.
Instead, they leverage telescopes. Haupt and her colleagues in Brookhaven's Instrumentation Department are well-versed in telescope technology, having built key components for the Vera C. Rubin Observatory—a mountaintop astronomy facility equipped with the world's largest digital camera—among many other astronomy projects.
Extract — continue reading at the source.
