Chapter 5 Quantum Aspects of Biophotonics

Interestingly, while adopted for a long time in the particle physics community as a usual gauge boson, the photon, i.e. the quantum particle associated with light, is still sometimes debated in the photonics community. Some weird questions are associated, like “is this photonic process quantum?”, “is it purely quantum?” or “is it non-trivially quantum?”. In the present chapter, we will not enter these discussions, but rather consider processes in which the state of a system is in a quantum superposition of different states (e.g. a Schroedinger cat) or in which distinct sub-systems are entangled (via non-locality).