BB84 protocol

The BB84 protocol is a quantum key distribution (QKD) method used to securely establish a cryptographic key between two separate parties. It relies on the fundamental principles of quantum mechanics to ensure the transmission cannot be intercepted.

The protocol uses polarized photons to transmit data, and any attempt to measure or intercept these photons will inherently alter their quantum state. Because of this physical law, the communicating parties can immediately detect the presence of an eavesdropper by checking for a high error rate.

The protocol was developed by Charles Bennett and Gilles Brassard. Its name, BB84, is derived from the creators' last names and the year 1984, when they initially conceptualized and published the quantum cryptography scheme.

Yes, modern implementations of the BB84 protocol frequently utilize standard commercial fiber optic networks to transmit the polarized photons. However, the maximum effective distance is limited by photon loss over the optical fiber without the use of quantum repeaters.