An Optical Emulation of the BB84 Quantum Key Distribution Protocol
JURPA 2026 Cover Image.
Abstract. Quantum key distribution (QKD) is an approach to secure communication that uses the principles of quantum mechanics to generate a shared secret key which can be used in encrypting messages. Unlike traditional cryptography, which relies on mathematical problems too computationally difficult for a classical computer to solve, an ideal QKD protocol can be secure even against the capabilities of quantum algorithms. The BB84 protocol, a famous implementation of QKD, uses the polarization states of photons to carry information. We constructed an accessible, fiber-optic-based apparatus that emulates the generation of a key through the BB84 protocol. Although a true demonstration of BB84 would require a single-photon regime, our many-photon system shows the information encoding, transmission, and basis-sifting steps of the protocol. Due to its accessibility and visual clarity, our apparatus is intended as an educational tool that makes each logical step of the protocol visible.
