SK Telecom announced that it has developed a dedicated relay device for quantum cryptography communication and succeeded in transmitting quantum cryptographic keys over an experimental network covering a round trip of 112 km from Bundang to Yongin and Suwon. By connecting multiple of the newly developed dedicated relay devices, quantum cryptography communication can be transmitted over distances ranging from hundreds to thousands of km.

Because quantum cryptography utilizes weak signals at the single quantum level, quantum key transmission was only possible up to about 80 km before the development of dedicated relay devices. Despite its excellent security performance, the 'distance limitation' acted as a major obstacle to the commercialization of quantum cryptography.

To overcome this, SK Telecom developed a dedicated quantum cryptography communication repeater (Trusted Repeater) and enabled the transmission of quantum cryptographic keys over distances of more than 80 km. For example, considering that the distance from Seoul to Busan is approximately 460 km, if five dedicated repeaters are installed, a quantum cryptographic key sent from Seoul can be received in Busan.

SK Telecom plans to partially deploy dedicated relay devices to its commercial network by the end of this year and gradually expand the coverage of its quantum cryptography communication services.



The fields where quantum cryptography can be applied are endless. Quantum cryptography services are highly utilized not only in telecommunications carriers' backbone networks but also in other industries where information security is essential, such as administration, national defense, finance, and healthcare.

SK Telecom is accelerating its efforts to pioneer the quantum cryptography market. Following the application of quantum cryptography technology to the wired sections of its commercial LTE network in Sejong City last year, the company began providing quantum cryptography services on parts of the Daedeok Advanced Science and Technology Network in May in cooperation with KISTI (Korea Institute of Science and Technology Information). Furthermore, it is currently in discussions with multiple domestic public institutions regarding the provision of quantum cryptography services.

"Quantum cryptography" is a communication encryption technology that utilizes the non-replicable properties of "quanta," the smallest indivisible unit of energy. It is known as a communication security system that cannot be breached by any existing hacking technology during transmission. The long-distance quantum cryptography technology demonstrated by SK Telecom has also been developed by countries such as China and the United States.

Park Jin-hyo, Head of the Network Technology Institute at SK Telecom, stated, “With the success of this long-distance quantum cryptography communication, Korea has now secured technology on par with advanced nations,” adding, “We will take the lead not only in developing core technologies but also in fostering a related ecosystem so that quantum cryptography communication can become a technology that represents Korea.”