qkd_bb84_simulator.py — Professional BB84 Quantum Key Distribution Simulator

qkd_bb84_simulator.py v1.3 — Professional BB84 Quantum Key Distribution Simulator

Features
• Zero extra setup — single file (only NumPy)
• Complete BB84 protocol with basis sifting and error checking
• Realistic depolarizing channel + photon loss (standard 0.2 dB/km fiber model)
• Intercept-Resend eavesdropping with rigorous information-theoretic bound
• Asymptotic secure key rate via binary entropy (Shor-Preskill style: 1 - 2h(QBER) - I_Eve)
• Privacy amplification via XOR folding (toy universal hashing)
• Generates final provably secure key
• High-resolution plot: secure key rate vs. fiber distance (independent simulations per point)
• Exports detailed statistics + secure key to JSON/CSV

Dependencies
• Requires numpy (>=1.21.0) — standard in scientific Python
• matplotlib (>=3.5.0) optional for --plot

Intended for cryptographers, quantum network engineers, and financial security teams designing provably secure quantum communication systems — provides accurate modeling of key rates, eavesdropping detection, and distance limitations that motivate quantum repeater development.

Real usage:
python qkd_bb84_simulator.py --bits 200000 --error_rate 0.015 --eve_present --verbose --plot
python qkd_bb84_simulator.py --bits 100000 --loss_prob 0.3 --output qkd_results.json

Made by Britt (2025) — MIT License