China's claim to a 'hack-proof' communication system

Chinese quantum satellite sends

The country successfully sent "hack-proof" messages from a satellite to the Earth for the very first time via the Micius satellite, which beamed the messages to two different receiving stations. Unlike traditional communications, which can be tapped surreptitiously, anyone attempting to eavesdrop on a quantum communication creates a disturbance that can be detected by the network's users. But, it was restricted by distance.

Quantum communication scientists have a fundamental interest in distributing entangled particles over increasingly long distances and studying the behavior of entanglement under extreme conditions.

Quantum Key Distribution system context diagram. By 2030, China hopes to achieve its ambitious dream of establishing a global cryptography-based communication network. The main advantage of this approach is that most of the photons' transmission path is nearly in vacuum, with nearly zero absorption and de-coherence.

"Satellite-based quantum key distribution can be linked to metropolitan quantum networks where fibers are sufficient and convenient to connect numerous users within a city over 100 km".

The satellite, called Quantum Experiments at Space Scale (QUESS), is claimed to be the world's first of its kind, and was sent into a sun-synchronous orbit on August 16, 2016. The distance between Delingha and Lijiang (Nanshan) is 1203 km. "I am not aware of any specific United States research that focuses specifically on ground-to-satellite quantum teleportation, [although] there have been experiments demonstrating quantum teleportation and pushing the limits of distance". A photon can not be perfectly copied and any attempt to measure it will disturb it. To optimize link efficiency, the scientists combined narrow-beam divergence with a high-bandwidth and high-precision acquiring, pointing, and tracking (APT) technique.

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This use of entangled photons is nothing new.

Pan further noted that quantum entanglement, which is the key technology used in quantum communications, has the potential to prevent wiretapping and enable secure communication.

China's breakthrough transmission traveled about 1,200 kilometers to Earth from space, making it up to 20 orders of magnitudes more efficient than an optical fiber of the same length would be.

Pan Jianwei, lead scientist of QUESS and an academician of the Chinese Academy of Sciences (CAS), said that the quantum satellite provides an experiment window of about 10 minutes when it flies over China.