Spin-selective optical interband excitation, which creates the spin polarization and detects the spin dynamics, has contributed to the considerable progresses for studying spin physics and controlling spins in bulk and structured semiconductors. Though the angular momentum transfer from a single photon to a single electron spin is an elemental process of the spin-selective excitation it has not been fully studied because of the difficulties to detect single photons and single electron spins. Gate-defined lateral quantum dots (QDs) are, however, suitable to detect a single electron spin in a single-shot manner and the coherent manipulation of single electron spins has been extensively studied in such QDs. Indeed we have realized the detection of single photoelectrons in a single quantum dot with a charge sensing technique. Moreover, the coherent coupling between single electron spin states and photon polarization states would allow us to investigate a quantum correlation between light and spin in solids and would contribute to long distance quantum communications. Here we show that single photoelectron spins can be discriminated by Pauli effect and the angular momentum of circularly polarized single photons can be transferred to single electron spins in lateral GaAs double QDs. These results manifest that photons can be coupled to electron spins in the electrically tunable QDs.
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