A single-photon source is a special type of light source that does not emit light in large quantities, but instead releases individual particles of light—called photons—one at a time. This is particularly challenging, because ordinary light sources such as lamps or lasers always produce many photons simultaneously.
Single photons are essential for modern quantum technologies. In quantum communication, for example, they can be used to transmit information with absolute security. Any disturbance of a single photon can be detected, which enables entirely new standards of data protection.
To generate single photons, special materials or artificial structures are used, such as individual atoms, solid state, or so-called quantum dots. These systems emit light in a highly controlled manner. As a result, they form an important foundation for future technologies such as quantum computers and quantum networks.
Single-photon sources are an excellent example of how precisely modern physics can operate today. They show that light does not have to be understood only as a continuous beam, but can also be described as consisting of individual, measurable particles.