  We report on a single photon and spin storage device based on a semiconductor
quantum dot molecule. Optically excited single electron-hole pairs are trapped
within the molecule and their recombination rate is electrically controlled
over three orders of magnitude. Single photons are stored up to 1 microsecond
and read out on a sub-nanosecond timescale. Using resonant excitation, the
circular polarisation of individual photons is transferred into the spin state
of electron-hole pairs with a fidelity above 80%, which does not degrade for
storage times up to the 12.5ns repetition period of the experiment.
