A physical graph representation of quantum optics experiments

Graph theory is a very good abstract descriptive tool for modelling and explaining phenomena from physics. Progress has also taken place in recent years in the direction of applying graph theory in quantum experiments for state generation with probabilistic sources [1-3]. In this work, we will talk about a highly advanced connection between graph theory and quantum experiments which goes beyond the original representation, by showing that a colored weighted graph can capture all the information of a quantum optical experiment [4,5]. This new physical and abstract representation allow us to discover various quantum information tasks with current photonic technology, including highly entangled quantum states, quantum measurement schemes, quantum communication protocols, and multi-particle quantum gates. The graph can be translated back at any point to an experiment consisting of optical elements, and we explicitly show how to translate it into several quantum optical experiments. In general, our physical graph-experiment representation gives us a different perspective on photonic quantum technologies, and is significantly useful for the design of future quantum experiments and applications in quantum information [4-5].