Detection and Generation of Non-Classical Light States from Single Quantum Emitters

Single photons are important states for quantum information processing and fundamental research.
These applications require efficient single-photon generation on demand. In this work a
single-photon device based on single InP and CdSe quantum dots is presented.

Intensity correlation measurements were used to verify the single photon emission in pulsed and
continuous operation. By using Fourier spectroscopy, the coherence length and spectral bandwidth of
the single-photon states was measured. The observation of cross-correlations between several
spectral lines revealed the existence of multi-photon cascades and gave information about their decay dynamics.

The efficient separation of adjacent photons from a two-level cascade allowed their independent use
and an effective doubling of the photon generation rate, similar to multiplexing in classical
information processing. For the first time, multiplexing on a single-photon level could be
demonstrated in a quantum key distribution experiment.