Quantum state transfer between a single photon and a single quantum in the solid state is needed to realize an essential constituent of quantum memory and quantum interface for the global quantum information network. The electron spin in quantum dots is a suitable candidate for such a purpose because of its long coherence time in solid state and matching to the optical communication wavelength. In this talk, we show the trapping and resetting of single photo-electrons in a single quantum dot and the detection of the photo-electron spin. The requisites for the quantum state transfer have been further realized in double quantum dots. First, the robust single photo-electron trapping has been demonstrated using non-destructive resonant inter-dot tunneling. Second, distinct one-to-one correspondence between circularly polarized single photons and single photo-electron spins has been shown.
 A. Pioda, E. Totoki, H. Kiyama, T. Fujita, G. Allison, T. Asayama, A. Oiwa, and S. Tarucha, Phys. Rev. Lett., 106 146804 (2011).