Quantum optics is a branch of physics that studies the behavior of light and its interaction with matter. It is a relatively new field of research, having only been developed in the late 20th century. Quantum optics is closely related to quantum mechanics, which is the study of the behavior of particles at the atomic and subatomic level. The two fields are closely intertwined, as quantum optics relies heavily on the principles of quantum mechanics. Quantum optics is used to study the behavior of light at the quantum level, such as the behavior of photons, the particles of light. It is also used to study the behavior of atoms and molecules when they interact with light. Quantum optics has a wide range of applications, from quantum computing to quantum cryptography. It is also used in the development of new technologies, such as quantum lasers and quantum computers.