In principle, a method that makes hacking or eavesdropping impossible
Success in modularization into integrated chips and component miniaturization through semiconductor processes

Core technology for wireless quantum cryptography communication has been developed in Korea for the first time.

The Electronics and Telecommunications Research Institute (ETRI) has developed core component technology necessary for wirelessly transmitting encryption keys in quantum cryptographic communication. While bulk optical components occupying a meter-sized area have been used until now, ETRI has succeeded in miniaturizing the components to a centimeter-sized or smaller, which is 1/100th the size of the existing ones, by applying a new integration method.

Quantum cryptography generates an encryption key by reducing the intensity of photons emitted from a laser source to the level of a single photon and transmitting them to a recipient. The principle involves generating, transmitting, and detecting the polarization and phase quantum states of the photons to create an encrypted key for both the sender and the receiver. Therefore, if hacking or eavesdropping occurs during transit, the quantum state changes, making hacking or eavesdropping impossible in principle.

The research team succeeded in developing core transmitting and receiving components that create, transmit, and detect polarized quantum states using light sources and polarizing components. As core transmitting and receiving components for wireless quantum cryptography communication, they implemented component modules including a 4-channel light source, a 4-channel polarization coupling/separation module, and a 4-channel single-photon detector.

In conventional quantum cryptography, individual components and devices such as polarization couplers, beam couplers, and half-wave plates that combine polarization states were included in the transmitting and receiving units, and the volume was large in the meter (m) range. However, ETRI modularized the functions of large components by implementing them into an integrated chip for the first time through semiconductor processes.

The core polarization coupling chip of the transmitter, successfully developed by the research team, measures 40mm x 2mm, significantly miniaturizing the four components that previously constituted the transmitter. ETRI created an integrated polarization module capable of generating multiple polarization states as a chip with one output for four inputs.

The system operating speed of the transmitting and receiving components created by the research team is currently 100 MHz, which is world-class.

In addition, existing transmitting and receiving components were expensive because they required combining multiple high-cost bulk individual components. There were also difficulties in aligning these individual components, but the component developed by this research team has resolved these issues. Therefore, it is expected to contribute significantly to the commercialization of quantum communication by enabling stability, mass production, and cost reduction.

Moving forward, the research team plans to demonstrate wireless quantum communication in a real-world environment early next year using the developed core transmitter and receiver components. Through this, the plan is to verify encryption key transmission rates of several hundred kbps and reduce the quantum bit error rate to within 5%, exceeding global standards.

ETRI plans to focus on further miniaturizing and integrating modules in the future, as well as improving the speed of quantum cryptographic key generation and transmission distance.

Yoon Cheon-ju, Project Leader of the Optical Communication Components Research Group at ETRI, stated, “In the era of the Internet of Things (IoT), where various devices such as mobile terminals and secure in-vehicle and inter-vehicle communication will be connected to communication networks, the transmission and reception of sensitive information will be made possible through quantum cryptography communication that guarantees perfect security.”

The wireless quantum cryptography components developed by ETRI are expected to be embedded in communication equipment and utilized as encryption devices in the future. In particular, they are projected to be useful for national administrative security networks, secure financial networks, encrypted transmission of military secrets, data center confidentiality, personal medical and information security services, and prevention of vehicle hacking.