Systematizing technology for transmitting quantum signals in real environments

A domestic research team has developed and systematized core integrated components for wireless quantum cryptography using its own technology, successfully transmitting and restoring quantum signals in real-world environments.

The Electronics and Telecommunications Research Institute (ETRI) announced that it has succeeded in transmitting and restoring quantum signals (photons) from a distance of more than 100 meters above the rooftop of Building 1 of the research institute, not only during the night but also during the day, using wireless quantum cryptography technology, a next-generation secure communication technology that can fundamentally block hacking.

The wireless quantum cryptography system technology recently developed by ETRI encodes information into photons, which are particles of light, and transmits and decodes them to generate encryption keys. If a third party intercepts the data, the quantum information is altered, making hacking or eavesdropping fundamentally impossible.

ETRI has successfully maintained an excellent quantum bit error rate (QBER) of 1% at night and 3% during the day at transmission distances exceeding 100 meters. The research team has secured technology capable of generating cryptographic keys at a rate of over 200,000 bits per second at 200 kbps.

The quantum bit error rate, which generally indicates the rate at which quantum signals are transmitted incorrectly, is 11% or less, and quantum cryptographic keys can be generated. The lower the error rate, the faster the encryption key can be generated, and a quantum bit error rate of 3% is very good performance.

Additionally, the research team explained that since the encryption key generated through quantum cryptography is used to encrypt high-speed data using a low-speed encryption key, the encryption key speed secured this time can be sufficiently utilized for data transmission at the level of tens of Gbps.

This announcement is significant in that it successfully restored quantum signals even during daylight, when sunlight is much stronger than the quantum signal. The ETRI researchers explained that by developing and applying ultra-noise reduction technology, they achieved excellent results, achieving a quantum bit error rate of less than 3% even during daylight.

In addition, ETRI is evaluated to have moved closer to commercialization by applying core components for integrated quantum cryptography communication, which it developed on its own at the level of several centimeters, to its system at the end of last year.

Miniaturization of core components of wireless quantum cryptography is an essential core technology for quantum cryptography to be applied in various fields in the future, such as drone-based systems and small terminal systems.

The wireless quantum key distribution system developed by ETRI has secured a significant portion of the technology required for operation in a real environment, and it is expected that the transfer of core technologies is possible at the current stage and that commercialization will be brought closer within one to two years. In the future, this technology can be used for communication within close range, such as between smartphones and bank ATMs, he explained.

However, the research team said that in order for wireless quantum cryptography systems to be commercialized in various fields such as long-distance as well as short-distance communication, additional research is needed on long-distance quantum signal transmission, mobile quantum communication technology, and development of convergence technology with modern cryptography, including encryption and decryption.

Furthermore, the research team first demonstrated the potential for hacking of a quantum cryptography system utilizing multiple lasers in a wireless quantum cryptography communication system. Furthermore, their method for preventing hacking and securing performance was published in Photonics Research, and was featured on the cover of the March issue.

Dr. Cheon-Ju Yoon, head of ETRI's wireless quantum cryptography research, said, "We will continue to research and develop ultra-small wireless quantum cryptography transmission and reception components that integrate a light source for wireless quantum communication, a polarization encoding module, a polarization decoding module, and a single photon detector, and to develop research technologies for small terminals and short-distance services."

Additionally, the research team explained that they plan to develop a wireless quantum cryptography communication system that can be used in mobile devices such as automobiles and drones, as well as a technology that can further increase transmission distance by utilizing small wireless quantum cryptography communication transceiver components.