Researchers at the National Institute of Standards and Technology have successfully transmitted entangled photons across 38.5 miles of existing network cable. This experiment marks a milestone for quantum networking because it occurred outside controlled laboratory conditions. The team sent light particles between NIST and the University of Maryland through aerial fiber-optic lines.
Aerial cables present significant challenges for quantum information because they remain exposed to wind, temperature fluctuations, and vibrations from traffic. These environmental factors typically distort the polarization of photons and break entanglement. Unlike standard internet data transmission, quantum states require extreme stability to maintain their integrity over long distances.
To overcome the noise in the environment, the researchers implemented a reference laser signal. By monitoring the distortion of the laser light, they calculated the necessary corrections for the entangled photons. This method allowed the system to remain stable for over 92 percent of the operation time. The experiment proved that existing infrastructure can host quantum protocols if the links receive active stabilization.
While the current transmission rate reaches up to 1,500 entangled photons per second, future efforts will focus on increasing speed through better hardware and more efficient software. The potential applications for this technology include linking telescopes into single instruments and creating unhackable communication channels. This test confirms that quantum networks are viable even in messy, real-world conditions.