This module is an exciting module: we meet our first protocol for quantum key distribution! This can be considered the highlight of this course – not only of this course, but of quantum cryptography. Or should we say, of quantum information? And what is maybe even more amazing is that, by now, you have developed all the knowledge that is needed to understand, and analyze, the protocol. So get ready for a feast:

In  6.2 we start off by giving you a gentle introduction to the important definitions and concepts used in quantum key distribution;

6.3 introduces you to so-called “BB84 states”, that will form the heart of the protocol;

6.4 describes the BB’84 protocol in detail, explaining each of the steps;

In 6.5 we begin our analysis of the protocol by considering a so-called purified form of the protocol;

6.6 (essentially) completes the security analysis via the use of a similar kind of guessing game as the ones we’ve already encountered;

Finally, in 6.7 we discuss the assumption that Alice and Bob have access to a classical authenticated channel, and how to do away with that assumption.

Before we get into all this – watch the next video module for a playful introduction to QKD and the BB’84 protocol!