April 21, 2026 -- As long as there's been an internet, there's been a way to hack it. Scientists have spent decades imagining a different kind of network, one where the laws of physics make eavesdropping physically impossible, not just technically difficult.

They call that dream a quantum internet.

A team at New York University, working with Brooklyn-based quantum startup Qunnect and Cisco, just took a step toward one, demonstrating for the first time that entangled quantum signals can be linked across multiple points using already-deployed telecom fiber.

A quantum network is created by transmitting information using individual particles of light. Any attempt to intercept a signal disturbs the particles and reveals the intrusion, a property that makes it far more secure than anything built on classical physics, like the internet of today.

One of the keys to making a quantum network into the vision of a quantum internet is a process called entanglement swapping, which allows particles that have never interacted become entangled, stitching together shorter links into a larger network. That step has long been a bottleneck.

“Our work shows we can connect quantum devices across a city using real infrastructure, not just in a lab,” said Tyler Cowan, a doctoral student working under Javad Shabani, director of NYU’s Center for Quantum Information Physics and the NYU Quantum Institute.

Cowan built one of the experiment’s entanglement sources and presented the team’s findingsopens in a new tab at the American Physical Society’s annual meeting in March.

The experiment builds on a 2023 demonstration in which NYU and Qunnect first showed that quantum signals could travel over commercial fiber between Brooklyn and Manhattan. This study goes further, adding a third node and entanglement swapping to connect those signals into something that begins to resemble a network.

The three-node proof-of-concept experiment connected two nodes at Qunnect's facility at the Brooklyn Navy Yard with one at QTD, a commercial data center at 60 Hudson Street in Manhattan that served as the network's central hub. The setup followed a hub-and-spoke design, in which simpler outer nodes connect through a more complex central node equipped with cryogenic detectors.

NYU's role was both experimental and strategic. Its researchers helped design the system, contributed one of the network nodes, and validated the quality of the entanglement produced across the city.

Qunnect provided the quantum hardware. The company’s Carina quantum networking solution includes entanglement sources and a system that stabilizes photon signals as they travel through fiber, which can shift with temperature and vibration. The collaboration builds on longstanding ties. Qunnect’s CEO Noel Goddard is an NYU Tandon School of Engineering alumnus and the company works closely with Shabani's lab.

Cisco contributed the orchestration software that synchronized the three sites into a functioning network.

The result was a successful demonstration of polarization entanglement swapping over deployed fiber, something not previously achieved at this scale. The system reached swapping rates of about 1.5 events per second across the city while maintaining the correlations needed for a working quantum network.

The experiment does not immediately deliver a quantum internet. But it tackles one of the field’s central challenges: how to reliably connect independent quantum devices over real-world infrastructure.

That challenge is especially acute outside the lab. Photons traveling through fiber are easily lost, and environmental noise can disrupt the fragile quantum states they carry. The team showed those effects can be managed well enough to sustain entanglement across a metropolitan network.

The system was also designed to scale. Because only the central hub requires specialized cryogenic equipment, additional nodes could be added without having to replicate that complexity—an important step toward practical citywide or data center-scale networks.

NYU already operates a local quantum network across Manhattan and is expanding it to additional campuses, including its Tandon School of Engineering in Brooklyn. It launched the NYU Quantum Institute last year, providing a cross-disciplinary hub focused on turning advances like this into deployable technologies.

In the near term, the most practical application among many is quantum key distribution—a way to share encryption keys that cannot be intercepted without detection. Longer term, similar networks could link quantum computers or enable new forms of sensing.

For Shabani, New York City is an ideal testbed.

“Manhattan is a very compact place,” he said. “Everything is within five or six miles, and you can find hundreds of financial institutions in a very small radius. That density—of infrastructure, institutions, and potential users—may make the city one of the first places where a quantum internet begins to take shape. Having this network right now is important. It’s a huge investment that will pay off probably in the next decade or so.”