QCBRIEF
Mirrors borrowed from a telescope now flex in real time to undo atmospheric blur, steering single photons into a hair thin fiber and adding a wireless leg to a US metro quantum network.
Researchers at Brookhaven National Laboratory and Stony Brook University demonstrated the first permanent free-space optical (FSO) quantum link in the United States, sending single photons and entangled photon pairs 13 miles (21 km) across open air between Stony Brook's Quantum Watchtower and Brookhaven's Quantum Lighthouse. The wireless leg adds a new path to the nation's longest metropolitan quantum network.
The architecture, according to Quantum Computing Report, starts with a 5-micron fiber core source expanded into a 25-inch (0.6-meter) primary mirror transmit beam. Kilohertz-rate deformable mirrors perform real-time adaptive-optics correction to undo atmospheric wavefront distortion, then refocus the beam into a 5-micron fiber at the receiver. Without that correction, thermal variation, wind, and ground structures would scramble the single-photon spatial mode and break the link.
The link uses infrared wavelengths native to atomic systems rather than the ~1550 nm telecom band, so future quantum processors and atomic-memory nodes can entangle across open air without wavelength conversion.
On August 19, 2026, at 12:26 a.m. ET, the Lighthouse recorded arrival of entangled photon pairs from the Watchtower; the team later validated daytime single-photon transmission, demonstrating 24-hour operability. Brookhaven's Instrumentation Department drew on telescope designs from the Vera C. Rubin Observatory to integrate the system.
The result is a single verified path, not a system. Multi-node scaling and longer-path testing are the next steps; satellite ground-station coupling is further out.