# Lecture 1

Figure 1.3 - A simple rule for updating

Professor Susskind introduces the following concepts:

• classical systems
• states (or configurations) of classical systems
• rules for updating classical systems

In particular, he considers the simplest type of physical systems, which are discrete. In this case, states are finite sets, and the rules for updating are permutations of the states.

He also introduces Dirac notation, which labels states as ket vectors.