The Electronics and Telecommunications Research Institute (ETRI) has reported a successful free-space quantum key distribution (QKD) in daylight with the self-developed polarization encoding chip for the first time. QKD is one of the most promising secure communication technologies, which encodes information into a single-photon, the smallest measurable unit of light. By using the quantum mechanical properties of the single-photon, quantum cryptography guarantees secure information exchange between the distant parties. The report is particularly worthy of attention in two points as follows.
First, ETRI's free-space QKD system works successfully even during the daylight whereas most other systems have failed to operate properly due to substantial amount of noise photons from sunlight. By developing and adopting elaborate noise filtering technologies, ETRI's QKD system achieved the secure key rate of 142.94 kbps with quantum bit error rate of 4.26% in daylight over the free-space distance of 275 m .
Second, ETRI's QKD system is configured with the self-developed polarization encoding chip, which dramatically reduces the size of the system compared to conventional QKD systems. Miniaturizing key components is highly important to make QKD systems to be used for the secure communication solution of several applications requiring light-weight such as Unmanned Aircraft Vehicle (UAV) and automotive cars, whose security is one of the critical concerns. The chip-based QKD component of ETRI is considered as a core technology for the commercialization of QKD system in various fields.
ETRI is now applying their integrated-chip technologies to other optical components to realize miniaturized QKD transceiver modules. Also, ETRI is trying to conduct the free-space QKD experiments for the extended transmission distance in daylight.