KT said on Monday it developed an in-house quantum key distribution device that can generate 300,000 encryption keys per second (300 kbps).

A quantum key distribution device can fundamentally block attempts to eavesdrop on physical lines because encryption keys cannot be copied due to quantum mechanical properties.

KT, which developed a quantum key distribution device with a speed of 150,000 keys per second in 2024, raised the key generation rate by more than double in 18 months. The company said it is the fastest speed among quantum key distribution systems made with domestic technology and offers the same performance as global manufacturers. If the device is introduced into a telecommunications network, it can provide quantum keys to more than 70,000 encryption devices in 1 minute.

A quantum key distribution system handles single photons, the minimum unit of light energy. That means quantum states can easily collapse when situations such as dispersion or scattering occur, which are characteristics of light.

KT developed an error-reduction filter and system to increase encryption key generation speed. A KT official explained, "By minimizing errors with the filter and system and generating and detecting quantum states at the desired time, it is possible to increase the key generation speed and improve system performance and reliability."

KT carried out related technical verification late last year for domestic quantum cryptographic communication technology development and certification bodies including the Telecommunications Technology Association (TTA), the Electronics and Telecommunications Research Institute (ETRI) and the National Information Society Agency (NIA).

It also carried out joint verification with a research team led by Professor Jun Heo (허준) at Korea University's Communications and Information Systems Laboratory, which specialises in quantum cryptographic communication technology. KT expects the error-reduction filter and system to be used in the quantum internet, a next-generation network.

Jong-sik Lee (이종식), head of KT's Future Network Research Institute, said, "KT will work to revitalise the domestic quantum industry market based on continued in-house development of quantum communication technology and technology transfer." He added, "We will continue efforts to secure future quantum internet technology."