  We demonstrate a prototype-implementation of deterministic information
encoding for quantum key distribution (QKD) following the ping-pong coding
protocol [K. Bostroem, T. Felbinger, Phys. Rev. Lett. 89 (2002) 187902-1]. Due
to the deterministic nature of this protocol the need for post-processing the
key is distinctly reduced compared to non-deterministic protocols. In the
course of our implementation we analyze the practicability of the protocol and
discuss some security aspects of information transfer in such a deterministic
scheme.
