Since the advent of quantum theory in the beginning of the 20th century, there is no other quantum mechanical phenomenon as much discussed as entanglement, a quantum state property related to the inseparability of quantum states into a product state. In contrast to classical theories following the paradigm of locality and determinism, entangled particles exhibits quantum correlations without any classical analogue, i.e., correlations which cannot be described in terms of a local deterministic theory. This phenomenon is often known as nonlocality. Apart from fundamental studies of nonlocality in nature, various concepts towards promising applications emerged in the domain of quantum information theory ¿ an unification of classical information theory and quantum mechanics ¿ incorporating nonlocality as working principle. In this PhD thesis, we discuss correlations between energy-time entangled photon pairs and explore consequences of high-dimensional entangled quantum states from an information-theoretic perspective.