What happened

Researchers at the U.S. Department of Energy’s Brookhaven National Laboratory and Stony Brook University have sent light particles carrying quantum information through open air between the two campuses — the first demonstration of its kind in the United States, according to a joint release.

On Friday, 21 August 2026, a daytime demo at Stony Brook’s rooftop Quantum Watchtower (Health Sciences Center) launched faint quantum states of light from an optical fiber core only about 5 microns across — less than one-tenth the width of a human hair — across 13 miles (21 kilometers) to Brookhaven’s Quantum Lighthouse in Upton, New York. Guests watched an ultrafast camera mark arrivals into an equally small receiving fiber after DOE Under Secretary for Science Darío Gil cut a ribbon at the aperture.

Nighttime tests went further. With lower background light, the team sent entangled photon pairs from a Stony Brook physics lab by fiber to the Watchtower, across the free-space link, and into detectors at the Lighthouse. Brookhaven’s own telemetry notes mark entangled arrivals at 12:26 a.m. ET on Wednesday, 19 August 2026.

The network this plugs into

PieceNumber
Free-space hop (Watchtower ↔ Lighthouse)13 miles / 21 km
Existing fiber quantum network161 miles / 259 km, eight nodes
Next planned free-space hop (Stony Brook ↔ Yale)~30 miles / 48 km across Long Island Sound
Fiber core emitting the photons~5 µm

The free-space optical (FSO) link is described as the first permanent U.S. link of its kind. It adds a wireless leg to what the labs call the nation’s longest metropolitan quantum network, already moving entangled pairs over commercial fiber across Long Island and the New York area.

How they kept the signal alive

Radio frequencies that carry classical wireless traffic are too noisy for fragile quantum states. The team used optical light and borrowed astronomy hardware: adaptive optics and rooftop telescope systems that correct atmospheric turbulence between sites that sit under more air than a typical stargazing path. Justine Haupt, Brookhaven’s lead scientist on the cross-institutional FSO project, put it plainly: the same technologies that let astronomers collect light are essential here — and the ground path is harder.

Eden Figueroa, director of Stony Brook’s Quantum Institute and a Brookhaven joint appointee, noted a second payoff: fiber networks are stuck on telecom wavelengths, while free-space links can use infrared bands closer to what quantum processors already speak. That is a route toward entangled atomic systems at distance.

Why it matters

Quantum networks matter when computers, sensors, and clocks need to share entanglement without trusting a classical channel. Fiber works, but only where fiber is. A permanent free-space hop is the classical internet’s wireless lesson applied to entanglement: span water, gaps, and last miles that cable does not reach — and, eventually, aim at satellites. Gabriella Carini, Brookhaven’s Associate Laboratory Director for Discovery Technologies, named satellite links as an ultimate goal for rural and remote coverage.

This is infrastructure, not a consumer product. The labs did not publish fidelity percentages, photon rates, or error budgets in the joint release. The claim that clears the bar today is detection of entangled photons after a 13-mile open-air path, on a permanent link bolted onto a 161-mile fiber backbone.

What to watch next

  1. Commissioning the Stony Brook–Yale 30-mile leg across Long Island Sound (Yale facility recently completed).
  2. Sustained, scheduled entanglement exchange — not one-night proofs.
  3. Connecting actual quantum processors at Brookhaven and Stony Brook over the combined fiber + free-space fabric.
  4. Published fidelity and rate numbers.

Sources