Concepts of Quantum Optics

Rajarshi Roy

Irene D’Amico

Warit Asavanant, Akira Furusawa

Basic concepts of quantum optics are introduced in this chapter. In the beginning, we give a review of the basic quantum mechanics. Then, we perform quantization of an electromagnetic field, which naturally introduces the concept of mode and quadrature. After that, we introduce basic quantum states of light and their phase space representation. Quantum operations in the continuous-variable system and their universality are also explained. To obtain the values of the physical quantities, we have to measure our quantum systems. In the optical continuous-variable system, homodyne measurement and photon number measurement are among the most common measurements that are also discussed here. Finally, we introduce the concept of quantum entanglement, which is one of the central concepts in quantum computation.

Michael G. Raymer, P. Polakos

The quantum nature of light enables potentially revolutionary communication technologies. A key to advancing this area of research is a clear understanding of the concepts of states, modes, fields, and photons. The concept of field modes carries over from classical optics, while the concept of state has to be considered carefully when treating light quantum mechanically. The term "photon" is an overloaded identifier in the sense that it is often used to refer to either a quantum particle or the state of a field. This overloading, often used without placing it in context, has the potential to obfuscate the physical processes that describe the reality we measure. We review the uses and relationships between these concepts using modern quantum optics theory, including the concept of a photon wave function, the modern history of which was moved forward in a groundbreaking paper in this journal by Iwo Białynicki-Birula, to whom this article is dedicated.