Restoration of photon indistinguishability in the emission of a semiconductor quantum dot

We report on a series of experiments on the second-order interference of two single photons emitted sequentially by a single quantum dot. The visibility of this interference probes the indistinguishability of the emitted photons; visibilities as high as 0.75 at $4\mathrm{K}$ have been achieved. At higher temperatures, dephasing of the quantum dot exciton degrades the indistinguishability of the emitted photons and the visibility of the interference. However, we demonstrate that engineering of the radiative lifetime of the quantum dot by the implementation of the Purcell effect in a microcavity, can restore indistinguishability and improve the visibility of second-order interference. At the same time, we demonstrate the resonant character of the Purcell effect.