Speaker
Description
We investigate the BB84 Quantum Key Distribution (QKD) protocol enhanced with a Vacuum+Weak decoy-state configuration through both simulation and a low-cost optical experiment. An interactive simulation built with Qiskit and Streamlit modeled key exchange under ideal, noisy, and adversarial conditions, while a separate decoy-state simulation quantified photon-number yields to reveal photon-number-splitting and beam-splitting attacks. Experimentally, a simplified free-space setup with attenuated laser pulses, polarization optics, and single-photon detectors implemented Vacuum+Weak BB84 using two mean photon numbers, enabling direct comparison of signal and decoy yields. While measured yields satisfied the expected decoy-state security conditions, observed quantum bit error rates (23–33%) exceeded the secure threshold (11%), preventing key extraction. Simulation analysis identified source instability, polarization misalignment, and suboptimal photon-number choices as key contributors to these high errors. These results illustrate both the potential and limitations of resource-constrained decoy-state QKD, and we propose improvements with stabilized lasers, matched polarization optics, fiber-coupled components, and extended simulations exploring alternative mean photon numbers, occurrence ratios, and additional QKD protocols.
