Chinese Team transmits Quantum-Encrypted Images over a Distance of 12,900 Kilometers:
A group of researchers from China has set a new record in Quantum Communication by using a lightweight microsatellite to transmit a secret encryption code over a distance of around 13,000 kilometers from China to South Africa. Pulses of laser light in specially prepared Quantum States were used for data transmission, which were sent from one rooftop in Beijing to another at Stellenbosch University in Cape Town. These light pulses were used to create a Quantum Key with which two images were encrypted. This record represents significant progress towards enabling secure communication between any location on earth, even over long distances, in the future. In the long term, this could form the basis for a global Quantum Network.
The Jinan‑1 microsatellite, which made the key exchange possible, was launched into orbit at an altitude of 500 km in July 2022. With a payload of around 23 kg, it is ten times lighter, 45 times cheaper and significantly more efficient than its predecessor, Micius, which was launched in 2016, explains Prof. Dr. Jian-Wei Pan, Quantum Physicist at the University of Science and Technology in Hefei. Micius was the first satellite to demonstrate an intercontinental Quantum Link. With Jinan‑1, Pan and his team also managed to reduce the weight of the ground station from 13,000 kg to just 100 kg, making it portable. The bidirectional satellite-ground optical communication is used for Quantum Communication, enabling key distillation and secure communication in real-time. Up to 0.59 million bits of secure keys can be transmitted in a single satellite pass. The microsatellite can be readily assembled on existing space stations or small satellites, paving the way for a satellite-constellation-based quantum and classical network for widespread real-life applications.
Despite the advances in weight, cost and distance, the microsatellite also brings with it a technical simplification: unlike its predecessor Micius, Jinan‑1 does not generate entangled photons, but uses a a simpler protocol. Entangled photons enable more secure encryption, in which the key remains hidden even from the satellite. This entanglement is also crucial for connecting Quantum Computers worldwide to form a global Quantum Network. Miniaturizing the technology for entanglement is more difficult, but Pan is convinced that the development of microsatellites with this equipment will be feasible in the future. China is planning to deploy more Quantum Communication Satellites for commercial applications one more in geostationary orbit in 2026. Click here for the publication.
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