A Virtualized BB84 QKD Simulator in Python Using Qiskit Aer for Education and Prototyping

Abstract

With the rapid advancement of quantum technologies, quantum key distribution (QKD) has become a key approach to secure communication. This study presents a software-only implementation of the BB84 QKD protocol developed in Python using IBM’s Qiskit Aer simulator. The proposed framework is designed for educational and prototyping purposes rather than for hardware-level security evaluation. The simulator models the core stages of BB84: random bit/basis generation, state preparation, basis-dependent measurement, sifting, and parameter estimation via QBER, followed by conceptual post-processing. Evaluation reports (i) the expected sifted-key ratio under random basis selection, (ii) the ideal-channel QBER behavior under noise-free Aer execution, and (iii) the theoretical intercept–resend detection probability derived from standard BB84 analysis. For sequences of ≥100 bits, the implementation matches standard BB84 expectations under ideal Aer execution: an expected sifted-key ratio of ≈50%, QBER → 0 in the absence of adversarial interference, and an intercept–resend detection probability above 99.9% for m = 100 disclosed verification bits. These results demonstrate that an idealized virtual environment can reproduce the BB84 measurement–disturbance trade-off in the information-theoretic sense, without claiming physical decoherence modeling unless an explicit Aer noise model is enabled. The analysis focuses on idealized BB84 behavior, where disturbance arises solely from basis mismatch and intercept– resend measurements rather than from physical decoherence or hardware noise models. The framework provides a reproducible platform for teaching and early-stage experimentation, with future work targeting realistic noise models and advanced post-processing.