Quantum Key Distribution via BB84 An Advanced Lab Experiment

Electronic communication has become one of the main pillars of modern society and their ongoing boom requires the development of new methods and techniques to secure data transmission. This has been the goal since the onset of cryptography in ancient times. Cryptography may be defined as the art of writing (encryption) and deciphering (decryption) messages in code in order to ensure their confidentiality, authenticity, integrity, and non-repudiation. However, current cryptography implementations provide only conditional security, relying on limited computational and technological capabilities of the opponent. This advanced-lab experiment presents the scheme for performing cryptography with unconditional security, based on fundamental laws of physics. In chapter 2 cryptography basics will be introduced in order to understand the weakness of ”public key cryptography” – mostly used for authentication today, e.g. in internet protocols – and the solution quantum mechanics provides by using ”quantum key distribution” (QKD). The quantum approach will be detailed by describing the theory of ”BB84”, the most widely applied quantum communication protocol (named after Charles Bennett and Gilles Brassard). Chapter 3 will introduce the experimental setup that will be used during the lab course. Finally, chapter 4 contains some suggestions how to use the setup.