Some specific areas of research into quantum information theory include:
- quantum computers and quantum computing
- quantum communication
- quantum cryptography
- quantum entanglement
- quantum teleportation
A key feature of quantum information theory is that the information contained in one system cannot be completely from one system to another - the information within the historical quantum states cannot entirely be retained once the system has collapsed from a superposition of states into a specific state. That lost information can never be retained, as opposed to classical theory where information transformations can be reversed to obtain a history of the previous states of the system.