Supervisors info:
Εμμανουήλ Φλωράτος, Ομότιμος Καθηγητής, Τμήμα Φυσικής, ΕΚΠΑ
Summary:
At the heart of quantum information lies the phenomenon known as entanglement, a property of a composite quantum system that opens the door to a plethora of applications. Besides the existence of this property, it is important for quantum computations to know how much entanglement we encounter in a system; thus, there is a need to find tools that will quantify entanglement, known as measures of entanglement. In this thesis, after discussing the prerequisites for such a measure, we initially study bipartite systems. We introduce the fundamental measure, which is the entanglement entropy, and two equivalent alternatives in the case of two qubits. Then we proceed to study mixed states, leading to two basic measures. The next step is to study three qubits. We analyze the distribution of correlations in such systems, discovering the 3-tangle, a measure of pure tripartite entanglement, as well as a general measure of entanglement. We find that entangled states of three qubits belong to one of two equivalence classes, called GHZ and W, and we prove the inequality of strong subadditivity.
