Experimental Semi-quantum Key Distribution With Classical Users

Quantum key distribution, which allows two distant parties to share an unconditionally secure cryptographic key, promises play important role in the future of communication. For this reason such technique has attracted many theoretical and experimental efforts, thus becoming one most prominent quantum technologies last decades. The security relies on mechanics therefore requires users be capable performing operations, as state preparation or measurements multiple bases. A natural question is whether what extent these requirements can relaxed capabilities reduced. Here we demonstrate a novel distribution scheme, where are fully classical. In our protocol, operations performed by untrusted third party acting server, gives access superimposed single photon, exchange achieved via interaction-free shared state. We also provide full proof protocol computing secret rate realistic scenario finite-resources, well practical conditions imperfect photon source detectors. Our approach deepens understanding fundamental principles underlying and, at same time, opens up new interesting possibilities for cryptography networks