Quench-induced supercurrents in an annular Bose gas.

We create supercurrents in annular two-dimensional Bose gases through a temperature quench of the normal-to-superfluid phase transition. We detect the magnitude and the direction of these supercurrents by measuring spiral patterns resulting from the interference of the cloud with a central reference disk. These measurements demonstrate the stochastic nature of the supercurrents. We further measure their distribution for different quench times and compare it with predictions based on the Kibble-Zurek mechanism.

Optically tunable spontaneous Raman fluorescence from a single self-assembled InGaAs quantum dot.

We report the observation of all-optically tunable Raman fluorescence from a single quantum dot. The Raman photons are produced in an optically driven Lambda system defined by subjecting the single electron charged quantum dot to a magnetic field in Voigt geometry. Detuning the driving laser from resonance, we tune the frequency of the Raman photons by about 2.5 GHz. The number of scattered photons and the linewidth of the Raman photons are investigated as a function of detuning. The study presented here could form the basis of a new technique for investigating spin-bath interactions in the solid state.