Quantum information

Summary

Quantum information is information carried by the state of a quantum system, and quantum information theory studies how it can be stored, transmitted and processed. Its basic objects are density matrices for states, quantum channels for processes and POVMs for measurements. Its basic unit is the qubit, a two-level quantum system. The theory explains tasks with no classical analogue, such as teleportation, and limits such as the impossibility of copying an unknown state.