High-performance semiconductor quantum-dot single-photon sources

Feynman's 1982 conjecture, that quantum computers can be programmed to simulate any local quantum system, is shown to be correct.

Quantum cryptography could well be the first application of quantum mechanics at the individual quanta level. The very fast progress in both theory and experiments over the recent years are reviewed, with emphasis on open questions and technological issues.

Quantum communication relies on the availability of light pulses with strong quantum correlations among photons. An example of such an optical source is a single-photon pulse with a vanishing probability for detecting two or more photons. Using pulsed laser excitation of a single quantum dot, a single-photon turnstile device that generates a train of single-photon pulses was demonstrated. For a spectrally isolated quantum dot, nearly 100% of the excitation pulses lead to emission of a single photon, yielding an ideal single-photon source.