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.