China has transmitted an “unbreakable” quantum code from a satellite to the Earth’s surface, in what Chinese state media is calling the foundation for a “hack-proof global quantum communications network”.
The breakthrough was reportedly reached by China’s Quantum Experiments at Space Scale (QUESS) satellite, nicknamed “Micius” after a 5th century BC Chinese philosopher. The satellite was launched in August 2016, with the US Pentagon calling it a “notable advance in cryptography research”.
Xinhua News Agency today announced that experiments conducted by the satellite had been successful, managing to send quantum keys to ground stations in north China’s Hebei Province, and northwest China’s Xinjiang Uygur Autonomous Region. The distances between the satellite and these stations varied between 646 km and 1,200 km, and the transmission rate is reported to be up to 20 times more efficient than using optical cables of the same length.
One fundamental benefit of quantum key distribution is what it means for communications security. Ciphers sent by the satellite would be unbreakable by current means, and attempts to hack into the data would result in useless information for the hackers, due to the nature of quantum information transfer. No matter what the computational power of potential hackers may be, any intercepted data would fall apart through being measured.
“Once intercepted or measured, the quantum state of the key will change, and the information being intercepted will self-destruct,” said Xinhua.
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Simone Severini, professor in Physics of Information at University College London, told Alphr that the achievement is “amazing news”:
“China is taking seriously the fact that quantum cryptography is simply the best currently available method to secure communication. Hopefully, this achievement will stimulate further research in quantum information and an increasingly stronger link between academia and industry.”
According to the lead scientist on the QUESS project, Pan Jianwei, the transmission rates achieved in the experiments “can meet the demand of making an absolute safe phone call or transmitting a large amount of bank data”.
“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,” Pan told Xinhua. “We can thus envision a space-ground integrated quantum network, enabling quantum cryptography – most likely the first commercial application of quantum information – useful at a global scale.”
A quantum network would need a number of advancements in basic computing ability before it can be rolled out to a global scale, let alone have any real commercial impact. China’s success looks to be a step closer to making that reality, however. The country’s state outlet said the results have been published in the journal Nature, where reviewers have called it a “milestone”.
Pan revealed that Chinese scientists will work with counterparts in European countries next month, to explore the potential for inter-continental quantum key distribution. There are also plans for China to launch more quantum satellites, with the aim of establishing an orbiting “constellation”.
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