Heo, Hyungjun Woo, Min Ki Park, Chang-Hoon Jang, Hyeong-Soon Hwang, Hyeon Lee, Hansuek Seo, Min-Kyo Kim, Sangin Kwon, Hyounghan Jung, Hojoong Han, Sang-Wook 2025-04-09T09:00:28Z 2025-04-09T09:00:28Z 2025-04-09 2025-03 2378-0967 https://pubs.kist.re.kr/handle/201004/152240 Quantum key distribution (QKD) systems have proven their theoretically unconditional security by quantum mechanics, but the scalability and cost barriers limit the rapid growth of the QKD system industry. The integration of QKD systems on chips has enabled their widespread adoption in secure quantum communication technologies, but the optimized platforms and designs are still being studied. Herein, we fabricated monolithic quantum photonic circuits for the BB84 QKD protocol using thin-film lithium niobate (TFLN), which enables flexible design in organizing both active and passive elements on one chip based on its superior material properties. The proposed circuit design for both transmitter and receiver parts are identical, which facilitates stable operation and mass production. Using our device, we demonstrated QKD over a field-deployed quantum channel, and its performance is comparable to state-of-the-art. This result proved the potential of TFLN for quantum communication technology. English AIP Publishing LLC | American Institute of Physics On-chip quantum key distribution over field-deployed fiber using lithium niobate photonic circuit Article 10.1063/5.0223694 1 APL Photonics, v.10, no.3 APL Photonics 10 3 Y scie scopus 001449777500003 2-s2.0-105000025718 Optics Physics, Applied Optics Physics Letter 2ND-HARMONIC GENERATION TRANSMITTER EFFICIENCY CONVERSION SECURITY