Fig. 3: Initialisation of a single electron spin.
a Level scheme of the negative trion X1− in a magnetic field (Faraday geometry). b Optical spin-initialisation via optical pumping on X1−. The measurement is carried out at B = 6.6 T. In the plateau centre, the resonance fluorescence disappears due to successful spin-initialisation; at the plateau edges it remains bright due to rapid spin-randomisation via co-tunnelling41. c Optical spin-initialisation and re-pumping with a second laser at a fixed frequency (laser 2). Recoveries of the signal are found in the plateau centre. d Schematic of the time-resolved spin-pumping measurement. e Resonance fluorescence intensity as a function of time. The signal drops due to optical spin-initialisation after turning the driving laser on. The overall intensity is larger when the time-delay τoff between the laser pulses is larger. In this case, the electron spin has more time to relax back from the off-resonant state. f Resonance fluorescence intensity as a function of the waiting time between the spin-pumping laser pulses. The magenta line is an exponential fit to the data (blue dots). From this measurement we extract an electron-spin lifetime of T1 ~ 48 ± 5 μs.
