Andreas V. Kuhlmann, Jonathan H. Prechtel, Julien Houel, Arne Ludwig, Dirk Reuter, Andreas D. Wieck, Richard J. Warburton
A semiconductor quantum dot mimics a two-level atom. Performance as a single photon source is limited by decoherence and dephasing of the optical transition. Even with high quality material at low temperature, the optical linewidths are a factor of two larger than the transform limit. It is shown here that the inhomogeneous contribution to the linewidth is caused by nuclear spin noise. This conclusion applies to both neutral and charged excitons. For the neutral exciton, we demonstrate an increase in the spin noise with increasing resonant laser power. Conversely for the charged exciton, we demonstrate a significant decrease in the spin noise with resonant laser power even without an external magnetic field. This noise reduction is exploited to demonstrate transform-limited optical linewidths even when the measurement is performed very slowly.
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http://arxiv.org/abs/1307.7109
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