  We demonstrate all optical electron spin initialization, storage and readout
in a single self-assembled InGaAs quantum dot. Using a single dot charge
storage device we monitor the relaxation of a single electron over long
timescales exceeding 40{\mu}s. The selective generation of a single electron in
the quantum dot is performed by resonant optical excitation and subsequent
partial exciton ionization; the hole is removed from the quantum dot whilst the
electron remains stored. When subject to a magnetic field applied in Faraday
geometry, we show how the spin of the electron can be prepared with a
polarization up to 65% simply by controlling the voltage applied to the gate
electrode. After generation, the electron spin is stored in the quantum dot
before being read out using an all optical implementation of spin to charge
conversion technique, whereby the spin projection of the electron is mapped
onto the more robust charge state of the quantum dot. After spin to charge
conversion, the charge state of the dot is repeatedly tested by pumping a
luminescence recycling transition to obtain strong readout signals. In
combination with spin manipulation using fast optical pulses or microwave
pulses, this provides an ideal basis for probing spin coherence in single
self-assembled quantum dots over long timescales and developing optimal methods
for coherent spin control.
