2. Implementation, state of the art

Since the first demonstration, quantum cryptography has evolved significantly, and several original implementations have emerged. A large proportion of these implementations were based on the BB84 protocol, which was polarization-encoded and ill-suited to transmission over optical fibers. In 2001, time-bin was introduced, enabling experiments in optical fibers for the first time. Since then, new protocols have been invented to enable more reliable implementation, or higher data rates than those achievable with the BB84 protocol.

In this section, we'll take a look at a few outstanding implementations.