Abstract Quantum optics is a powerful tool both for investigations of fundamental questions about the nature of quantum correlations and for the developments of fascinating new applications in quantum communication. It is known since at least the famous EPR paper of 1935 that quantum correlations have very peculiar features, known as quantum non-locality. The last 15 years have seen a number of photonics experiments ruling out various alternative models, thus confirming the extraordinary accuracy and counter-intuitive predictions of quantum theory. In parallel, the same experimental tools have allowed one to develop a completely new way of establishing secret cryptographic keys between two distant partners. Conceptually, the security of quantum cryptography – as this application is known – is close to quantum non-locality. Yet, this close connection to foundations hasn’t prevented quantum cryptography to become commercial and find niche markets.