Quantum Information Theory or Quantum Shannon Theory is the combining is the study of where quantum mechanics and information theory converge. It will most likely take on more and more relevance as technology progresses towards quantum computing. A great resource to read is From Classical to Quantum Shannon – Theory Mark M. Wilde. It goes into what is quantum information and how it is broken down into what is know as a q bit.
In information theory a piece of information is called a bit and in Quantum theory or Quantum Information Theory a piece of information is called a qubit.