  These notes introduce a handful of core ideas from quantum information
science that figure prominently in modern research on quantum gravity. The
central concept that forms the base of these notes is that of a quantum
channel; that is, the most general physically-reasonable map between quantum
states and between operators on Hilbert space. After reviewing some
fundamentals, we will study channels and their properties, and then go on to
formulate quantum error correction in terms of quantum channels. Along the way,
we will see how a handful of problems in high energy physics, such as the black
hole information problem and bulk reconstruction in AdS/CFT, can be cast in the
information-theoretic language being set up.
