The electron spin is a fundamental digital unit that can be utilized to store and to process information. Practical applications require long spin life-times and large spin polarizations without the need of strong external magnetic fields and at temperatures as high as possible.
The talk deals with a resident electron in a charged quantum dot. Since largely isolated from the environment, spin-orbit interaction that limits the electron spin life-time in bulk semiconductors is strongly suppressed here. Steady-state single-spin polarizations as large as 0.5 can be created by optical pumping.
The electron spin is coupled by the contact hyperfine interaction to the nuclear moments of the lattice atoms in the quantum dot. The formation of zero-field nuclear spin polarization as well as its subsequent decay by the dipole-dipole interaction is directly resolved in time up to about 100 K. The findings demonstrate the potential of controlling optically the spin state of the nuclear ensemble and to use it as a long-lived quantum memory as well.