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Free-Space Reference Frame Independent Quantum Key Distribution System With Photonic Integrated Circuit-Based Transmitter
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- Authors
- Kyongchun Lim, Minchul Kim, Byung-Seok Choi, Ju Hee Baek, Joong-Seon Choe, Kap-Joong Kim, Dong Churl Kim, Junsang Oh, Chun Ju Youn
- Issue Date
- 2026-02
- Citation
- Journal of Lightwave Technology, v.44, no.3, pp.1079-1085
- ISSN
- 0733-8724
- Publisher
- IEEE
- Language
- English
- Type
- Journal Article
- Abstract
- Deployable quantum key distribution (QKD) for free-space link must be both reference frame tolerant and hardware compact, yet existing free-space implementations still rely on bulk optics and active alignment. To address this gap, we develop the first reference frame independent (RFI) QKD transmitter fully integrated on a photonic-integrated circuit (PIC) and packaged in a CFP2 optical-transceiver form factor. The PIC incorporates a six-channel laser diode array, a six-channel variable optical attenuator array, and a polarization beam combiner, providing wavelength indistinguishability and high polarization fidelity. Combined with a micro-optics based polarization decoder and a bidirectional two-stage pointing, acquisition, and tracking (PAT) system, the PIC transmitter forms a complete free-space RFI QKD system. Based on the system, RFI QKD is performed with 10 m free-space channel, providing that QBERs measured in the same basis are below 3.81 % and the security parameter is 1.77±0.02 . This leads a stable secret key rate of 77.33±1.65kbps for 100 s. These results verify the feasibility of PIC-based RFI QKD transmitter and establish a clear pathway toward fully deployable PIC-based QKD systems.
- Keyword
- Free-space QKD, photonic integrated circuit (PIC), quantum key distribution (QKD), reference frame independent (RFI) QKD
- KSP Keywords
- Active Alignment, Beam combiner, Bulk optics, Circuit-based, Distribution System, Form factor, Quantum Key Distribution, Space link, Two-Stage, Variable optical attenuators(VOAs), free space