Bb84 quantum key distribution system and method based on passive polarization encoding

Abstract

This invention relates to quantum key distribution, specifically to a BB84 quantum key distribution system and method based on passive polarization coding, including a transmitter Alice, a receiver Bob, and a quantum channel. The transmitter Alice includes a passive coding transmitter, which comprises a predictive single-photon source module and a fully passive polarization coding module. The predictive single-photon source module generates signal-idle single-photon pairs. The signal photon is detected by a single-photon detector, and its detection event serves as the prediction time reference for the entire system. The idle photon enters the fully passive polarization coding module. The fully passive polarization coding module randomly assigns the idle photon to the corresponding optical path and maps it to one of the four polarization states of BB84 within the optical path, while making each polarization state correspond to a fixed time delay, forming a time delay tag. The technical solution provided by this invention can effectively overcome the shortcomings of existing technologies that are difficult to simultaneously achieve complete passivity, high security, low system complexity, and engineering practicality.

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