Nonclassical Radiation from a Single Quantum Dot

We report the experimental observation of photon antibunching in the photoluminescence of a chemically synthesized CdSe/ZnS quantum dot (QD) at room temperature and from a single self-assembled InAs/GaAs QD at 4 K. These results prove that a single quantum dot acts like an artificial atom, with a discrete anharmonic spectrum. Using the quantum regression theorem, we find that the normalized second-order correlation function g(2)(τ) can be described by a single exponential function in the weak-laser excitation regime. From this model we derive that the time constant of the photon antibunching signal is determined by the effective incoherent pump and recombination rates of the nonresonant optically pumped QD.