Quantum Cryptography Based on Split Transmission of One-Bit Information in Two Steps

We propose a simple quantum cryptographic scheme involving truly two orthogonal states. The security of the protocol is based on splitting the transfer of one-bit information into two steps, ensuring that only a fraction of the bit information is transmitted at a time. A particular implementation with an asymmetric interferometer is presented, which does not require the random timing of the packet sending as was used by Goldenberg and Vaidman [Phys. Rev. Lett. 75, 1239 (1995)].