Department of Electrical Engineering, Graduate Institute of Photonics and Optoelectronics, and National Taiwan University (NTU), Taipei 10617, Taiwan R.O.C
Kuan-Wei Hu
Department of Electrical Engineering, Graduate Institute of Photonics and Optoelectronics, and National Taiwan University (NTU), Taipei 10617, Taiwan R.O.C
Hsing-Yi Huang
Department of Electrical Engineering, Graduate Institute of Photonics and Optoelectronics, and National Taiwan University (NTU), Taipei 10617, Taiwan R.O.C
Yueh-Hsun Yang
Department of Electrical Engineering, Graduate Institute of Photonics and Optoelectronics, and National Taiwan University (NTU), Taipei 10617, Taiwan R.O.C
You-Xin Wang
Department of Electrical Engineering, Graduate Institute of Photonics and Optoelectronics, and National Taiwan University (NTU), Taipei 10617, Taiwan R.O.C
Shih-Chang Hsu
Department of Electrical Engineering, Graduate Institute of Photonics and Optoelectronics, and National Taiwan University (NTU), Taipei 10617, Taiwan R.O.C
Chih-Hsien Cheng
National Institute of Information and Communications Technology, Tokyo, Japan
Atsushi Matsumoto
National Institute of Information and Communications Technology, Tokyo, Japan
Kouichi Akahane
National Institute of Information and Communications Technology, Tokyo, Japan
Yuh-Renn Wu
Department of Electrical Engineering, Graduate Institute of Photonics and Optoelectronics, and National Taiwan University (NTU), Taipei 10617, Taiwan R.O.C
Hao-Chung Kuo
National Yang-Ming Chiao-Tung University, Hsinchu 30010, Taiwan R.O.C
Gong-Ru Lin
Department of Electrical Engineering, Graduate Institute of Photonics and Optoelectronics, and National Taiwan University (NTU), Taipei 10617, Taiwan R.O.C
An adaptive differential-phase-shifting (DPS) quantum key distribution (QKD) protocol improved by encoding asynchronous-bit-rate with harmonic clock tunability, decoded by shortened delay-line interferometer (DLI) with enhancing stability, and received by single-photon detection with long hold-off is demonstrated to realize low-erroneous transmission. To achieve long-term stabilized visibility with a maintained quantum bit-error-ratio (QBER) and secure key rate, the shortened and polarized DLI enlarges its free-spectral range (FSR) and reduces its power-to-wavelength slope (δP/δλ) to suppress its sensitivity to thermal gradient, channel leakage, and wavelength disturbance. Extremely low power and wavelength drifts of ΔP/P < ±0.02% and Δλ/λ = ±6.45 × 10−8 can be achieved, even when using a single-mode QKD carrier with a relatively broadened 300-kHz linewidth. Flexibly expanding the 1-bit-delay FSR of the polarized DLI from 0.04 to 1.00 GHz improves its immunity to environmental disturbances, enabling the DPS-QKD decoding with 210–213 patterns, 3.2% QBER, and 17.46-kbit/s under 0.22 photon/pulse in average. The asynchronous-bit-rate DPS-QKD protocol enables harmonic expansion of DLI’s FSR at limited single-photon avalanche detector’s bit rate, which lengthens the duration of stable visibility to support long-pattern DPS-QKD.
