Fig. 1: Continuous-variable quantum passive optical network (CV-QPON) architecture and operation.
a The provider encodes key information onto quadratures of the coherent state. This state is broadcast to N users through an insecure quantum channel, under the potential control of Eve. The channel’s properties include transmittance η and Eve-induced excess noise, ϵ. Users employ coherent detection, decoding key information from the coherent state’s quadrature values (x and p). The detectors are characterized by quantum efficiency τ and electronic noise v. All classical communications occur via a classical authenticated channel in a centralized manner. b The protocol encompasses a quantum prepare-and-measure phase, followed by data processing. After these steps, Alice and each user will share a symmetric key Kl, which can be used for cryptographic tasks
