Abstract

An electron spin in a quantum dot is a promising candidate realization of a quantum bit. In the last few years, this promise is gradually coming true. Electrical single-shot read-out of the electron spin has now become routine in our lab. We have used this read-out capability to characterize the spin relaxation time, finding T1’s of the order of 1 ms, presumably dominated by the spin-orbit interaction. Furthermore, from transport measurements through two dots in series, we found that the electron spin dephases in a time as short as 25 ns, due to the hyperfine interaction with the nuclear spins in the substrate. Fortunately, the nuclear dynamics is very slow, so the intrinsically long T2 of electron spins can be recovered via spin-echo-style techniques, as demonstrated by the Harvard group. Finally, we have very recently observed magnetic resonance of the electron spins in a double quantum dot, by applying microwaves on-resonance with the Zeeman splitting.