Matt Williams, Undergraduate Maths Seminar
Throughout history the desire to securely share secret messages has driven research into cryptography; from the simple Caesar cipher to the Public Key Cryptography systems that protect our credit cards every time we buy textbooks on Amazon. The discovery of quantum mechanics at the start of the last century fundamentally changed the way we think about the world around us.
More recently it also changed the way we think about computing and information theory. Quantum computers will render useless many of the codes upon which we currently depend. Fortunately some of the weird aspects of quantum theory can be put to use to do cryptographic tasks with security guaranteed not by computational complexity but by the laws of physics. Assuming only a reasonable knowledge of linear algebra I hope to introduce some of these phenomena then look at how QM can be used to securely distribute a key and help us to be truly random.