ABSTRACT
A standard laser produces a coherent state of light with a Poissonian photon number distribution. Generation of single photons on demand is a key requirement for quantum key distribution and quantum information processing systems based on photonic qubits. One of the generation schemes for single photons is to use a single semiconductor quantum dot embedded in a monolithic microcavity. An optical pump pulse or electrical pump pulse generates more than one electron–hole pairs in a quantum dot. Those electron–hole pairs recombine to generate photons one by one via spontaneous emission. The last photon emitted from a quantum dot has a unique wavelength, differing from the other photons, because the multiparticle interaction inside a quantum dot modulates an emission wavelength. One can selectively extract this last photon by a narrow band optical filter, so that single photons are extracted from the system no matter how many electron–hole pairs are injected into the quantum dot initially.
