Quantum correlation among photons from a single quantum dot at room temperature

Maxwell's equations successfully describe the statistical properties(1,2) o f fluorescence from an ensemble of atoms or semiconductors in one or more d imensions. But quantization of the radiation field is required to explain t he correlations of light generated by a single two-level quantum emitter, s uch as an atom, ion or single molecule(3-6). The observation of photon anti bunching in resonance fluorescence from a single atom unequivocally demonst rated the non-classical nature of radiation(3). Here we report the experime ntal observation of photon antibunching from an artificial system-a single cadmium selenide quantum dot at room temperature. Apart from providing dire ct evidence for a solid-state non-classical light source, this result prove s that a single quantum dot acts like an artificial atom, with a discrete a nharmonic spectrum. In contrast, we rnd the photon-emission events from a c luster of several dots to be uncorrelated.