Quantum information and entanglement
Quantum entanglement is one of the central features of quantum mechanics that can not be observed in classical systems. The current interest in entangled states, however, is not only based on their importance for the quantum-classical transition, but also on their importance for many application of quantum information processing, such as quantum teleportation or measurement-based quantum computing.
We will introduce the basic notions of separable and entangled states and identify entanglement as correlations beyond the classical framework. With the concept of quantum channels we will define entanglement measures, i.e. quantities that quantify quantum correlation and distinguish them from classical ones. On the basis of some exemplary measures we will illustrate why the distinction between classical and quantum correlations typically requires a minimization and outline approaches to solve such optimization problems. Eventually we will discuss the impact of decoherence on the stability of entanglement and show how classical correlations emerge at the cost of quantum correlations.