Quantum key distribution (QKD) is a cutting-edge way to secure communications. It uses quantum physics to create unhackable keys. A new study shows a big step forward for this technology.
Researchers have now sent these unhackable keys over 120 kilometers (about 75 miles). They used tiny light sources called quantum dots. This breakthrough could lead to a truly secure quantum internet.
Sending Unhackable Keys Over Long Distances
An international team from Germany and China made this happen. They used a method called time-bin encoding. This means information is stored in the timing of single light particles, or photons. This method is very stable, even in noisy fiber optic networks.
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Start Your News DetoxThe team used a special semiconductor quantum dot device. It creates single photons that are then encoded. On the other end, a receiver decodes these photons. This system worked continuously for over six hours.
The system achieved the highest secure key rate ever for this type of QKD using quantum dots. It generated about 15 bits per second. This is enough to encrypt things like text messages. Even after traveling 120 km, the error rate was kept below 11%.
Why This Breakthrough Matters
The researchers highlighted the importance of their findings. Quantum dots that emit light in the telecom band are good for fiber communication between cities. They can be built into practical QKD systems.
Many current QKD systems struggle with environmental changes like temperature or vibrations. They need constant adjustments. But time-bin encoding is naturally stable. It doesn't need complex compensation.
The system's ability to run for six hours straight shows how robust it is. This includes its Sagnac interferometer and active feedback control. This work proves that quantum dot sources can be used in stable, real-world QKD systems. It's a big step toward secure quantum communication networks.
Deep Dive & References:
Time-bin encoded quantum key distribution over 120 km with a telecom quantum dot source - Light: Science & Applications, 2026
