Carbon nanotube single-photon source

An atom, molecule, atomic layer, or molecular layer is adhered to a carbon nanotube surface, or the surface is doped with the atom, molecule, atomic layer, or molecular layer, to form a deep localized level so that an exciton is localized. Alternatively, an atom, molecule, inorganic or organic substance of an atomic or molecular layer, a metal, a semiconductor, or an insulator is absorbed to, deposited on, or encapsulated in the carbon tube inside surface to make permittivity of the portion undergoing the absorption, deposition, or encapsulation higher than that of a clean portion free of the absorption, deposition, or encapsulation so that binding energy of the exciton in the clean portion is high, or reduce a band gap of the portion undergoing the absorption, deposition, or encapsulation so that the exciton is confined and localized in the clean portion or the position undergoing the absorption, deposition, or encapsulation.