  Electron spins in GaAs quantum dots have been used to make qubits with
high-fidelity gating and long coherence time, necessary ingredients in
solid-state quantum computing. The quantum dots can also host photon qubits
with energy applicable for optical communication, and can show a promising
photon-to-spin conversion. The coherent interface is established through
photo-excitation of a single pair of an electron and a Zeeman-resolved
light-hole, not heavy-hole. However, no experiments on the single photon to
spin conversion have been performed yet. Here we report on single shot readout
of a single electron spin generated in a GaAs quantum dot by spin-selective
excitation with linearly polarized light. A photo-electron spin generated from
a Zeeman-resolved light-hole exciton is detected using an optical spin blockade
method in a single quantum dot and a Pauli spin blockade method in a double
quantum dot. We found that the blockade probability strongly depends on the
photon polarization and the hole state, heavy- or light-hole, indicating a
transfer of the angular momentum from single photons to single electron spins.
Our demonstration will open a pathway to further investigation on fundamental
quantum physics such as quantum entanglement between a wide variety of quantum
systems and applications of quantum networking technology.
