Enhanced Quantum Key Distribution Protocols Using BB84 and B92

Abstract

Four-state quantum key distribution (QKD) protocol BB84 [1] and two-state QKD protocol B92 [2] can let Alice and Bob share the secret key with idealized maximum efficiencies 50% and 25% over quantum channel, respectively. However, for these two polarization-based systems, the polarization states need to be maintained stable and against the noise of photon over a long distance optical fiber. Due to the alignment of polarization and the need of apparatus, the complexity of a four-state protocol is greater than that of two-state protocol. We herein use average number of polarization states in a QKD protocol as the complexity order. In this paper, we propose two enhanced QKD protocols. One is to enhance the idealized maximum efficiency to 28.6% with the average complexity order 2, and the other has the efficiency 42.9% and the average complexity order 2.86.