Quantum Information and Security

Full course description

In this course we will consider the power of quantum mechanics not in accomplishing computational or ‘algorithmic’ tasks, but instead for communication- and security-related tasks. The strange properties of the quantum world turn out to be remarkably useful for these. For example, we can exchange secret messages in a way that is unconditionally secure: secrecy is guaranteed by the physical laws of nature, rather than (as in ordinary cryptography) based on an assumption that a particular computational problem is too hard for the adversary.

We will begin by covering the theoretical techniques needed to study security-related protocols, where it is fundamental that some parties will not know what state a particular quantum system is in. After a thorough grounding in the ‘density matrix’ formalism which is used to represent this uncertainty, we will cover quantitative measures of this kind of uncertainty, for instance quantum versions of classical entropy. We will then look at a variety of protocols (e.g. quantum money, quantum key distribution,…), and how to define and prove the desired properties.