Researchers from the National Institute of Standards and Technology (NIST), the Joint Quantum Institute (a partnership between NIST and the University of Maryland), and the company Qunnect have demonstrated that fragile quantum entanglement can survive transmission through real-world, noisy fiber-optic infrastructure. They sent entangled photons over 62 kilometers (about 38.5 miles) of commercial fiber stretching from NIST’s Gaithersburg campus to the University of Maryland in College Park. The challenge was that much of the fiber was above ground and exposed to environmental factors like temperature fluctuations and wind, which typically distort quantum states. To overcome this, the team implemented a real-time stabilization system developed by Qunnect: it sent reference light beams through the fiber to measure polarization changes and then applied 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 that the photons detected at each end had indeed remained entangled. Yicheng Shi, a physicist at NIST and the study’s lead author, described this as «a stress test of quantum networking systems» — a demonstration that quantum networking protocols can work in real-world environments. This is a crucial step toward building practical quantum networks for secure communications, distributed quantum computing, and sensor networks
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