SK Telecom tests quantum repeater, breaks distance barrier

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SK Telecom announced that it has developed a powerful quantum repeater that has set a new distance record for transmitting quantum communication over an optical fiber network.

SK Telecom says its “Trusted Repeater” achieved a milestone in the field of quantum cryptography technologies by extending the distance record for Quantum Key Distribution (QKD) to 112 km via a roundtrip on a pilot fiber-optic network connecting Bundang, Yongin and Suwon.

The previous maximum transmission distance of QKD on a fiber network was around 80 km, due to the fact that it involves the use of weak single-photon quantum signals. Consequently, the distance limitation of QKD for fiber had been viewed as the biggest obstacle to its commercialization.

Last week, China’s state news agency Xinhua reported that a Chinese satellite transmitted quantum communications over a distance of 1,200 km, which  now stands as the current record distance for quantum communications transmission.

SK Telecom hopes the Trusted Repeater will help make quantum cryptography communication viable for terrestrial fiber. The cellco said it could transmit quantum keys from Seoul to Busan, which are approximately 460 kilometers apart, by installing five units of its repeaters.

Quantum cryptography communication is said to be the most secure form of communication encryption that cannot be broken with any existing hacking technology. SK Telecom says it expects quantum cryptography to replace existing security solutions for just about every sector, from national defense and  finance to self-driving vehicles and the Internet of Things.

The company plans to work with its global partners to apply quantum cryptography solutions, including the quantum repeater, for commercial LTE networks – not just its own network in Korea but overseas networks as well.

SK Telecom says it applied its quantum cryptography technologies to its commercial LTE network (fiber optic cable) in Sejong City in 2016, as well as some parts of the advanced science and technology research network (SuperSiReN) in Daedeok Research Development Complex via cooperation with the Korea Institute of Science and Technology Information (KISTI) last May.

SK Telecom also says it has been actively developing core quantum cryptography technologies since it established Quantum Tech Lab in 2011. Moreover, in February 2017, it entered into an agreement with Nokia to cooperate in quantum cryptography, and established the Quantum Alliance with Deutsche Telekom.

Park Jin-hyo, senior vice president and head of SK Telecom’s Network Technology R&D Center, said the company “will continue to focus on developing key quantum cryptography technologies and building a related ecosystem.”

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