NIST sends ‘spooky’ quantum link from Gaithersburg to College Park

Entangled photons successfully traveled 62 kilometers (about 38.5 miles) through commercial fiber optic cables stretching from the National Institute of Standards and Technology (NIST) in Gaithersburg to the University of Maryland in College Park. This achievement, reported in the Journal of Optical Communications and Networking, demonstrates the survival of fragile quantum entanglement in real-world conditions, a key step toward building a quantum network. NIST physicist Oliver Slattery described the fiber optic lines as “about as bad a connection as you can possibly have,” yet the signals still arrived. Researchers completed this transmission in early 2025.

Entangled Photons Distributed Through 62 Kilometers of DC Fiber

The ability to maintain quantum entanglement over significant distances represents a crucial step toward practical quantum networking, and researchers recently demonstrated this feat using existing, imperfect infrastructure. The team addressed this issue by implementing a real-time stabilization system developed by Qunnect, which actively corrects for distortions. This system sends reference light beams through the fiber, measures polarization changes, and then applies inverse transformations to the entangled photons, preserving their quantum link.

The experiment achieved a distribution rate of 1,500 entangled photons per second, with a 92.8% success rate, requiring corrections 7.2% of the time. A statistical test confirmed the photons remained entangled despite the noisy environment.

A European group previously achieved entanglement over 248 kilometers of underground fiber, but this new study is notable for its use of above-ground cables, which more closely represent the conditions future quantum networks will face. “I would call this a stress test of quantum networking systems,” explains Yicheng Shi, a physicist at NIST and the study’s lead author. Amazingly, it still worked. It’s a demonstration that quantum networking protocols can work in real-world environments.” This successful transmission underscores the potential for building quantum networks on existing infrastructure.

NIST & Qunnect Stabilize Polarization in Real-Time Transmission

Researchers are actively working to establish quantum networks capable of enhancing scientific research, bolstering computing power, and securing communications; however, maintaining the delicate entangled states of photons during transmission remains a significant challenge. The fiber used in the experiment presented considerable obstacles, as much of it was suspended from poles and exposed to environmental factors like temperature fluctuations and wind. Maintaining polarization is critical because entangled states are often encoded within it, and fiber distortions can disrupt this delicate encoding.

Quantum Entanglement Achieves 92.8% Distribution Rate

Researchers achieved 92.8% success in distributing entangled photons over a 62 kilometer commercial fiber optic link between NIST’s Gaithersburg campus and the University of Maryland in College Park. This achievement signifies a move beyond laboratory conditions toward practical quantum communication systems. Unlike classical networks, which rely on light intensity unaffected by disturbances, quantum networks encode information in photon polarization, making them particularly vulnerable to fiber distortions. Polarization corrections were needed 7.2% of the time. Statistical analysis confirmed the photons demonstrably remained entangled despite the challenging conditions.

Applications of Long-Distance Entanglement for Future Networks

The potential of quantum networks extends far beyond theoretical physics, promising to reshape diverse fields from astronomy to medicine. Researchers are actively pursuing methods to maintain fragile quantum entanglement, a phenomenon Albert Einstein famously termed “spooky action at a distance”, over significant distances, and recent progress indicates practical deployment may be closer than anticipated. These long-distance links could revolutionize astronomical observation; entangled photons shared between telescopes separated by thousands of kilometers would effectively create a much larger aperture, yielding dramatically sharper images of distant celestial objects.

Similarly, networks of entangled sensors could detect subtle seismic activity, potentially providing early warnings for earthquakes or volcanic eruptions. Perhaps most significantly, entangled quantum computers, networked together, could tackle computational problems currently intractable for even the most powerful supercomputers, accelerating drug discovery and materials science.

Ultrasecure communication networks represent another compelling application, where any attempt to intercept data would immediately disrupt the entanglement, alerting users to a breach. To realize these benefits, the NIST team confronted the challenge of preserving entanglement in a realistic, “noisy” environment.