Fig. 2

Real-time detection of Pauli spin blockade and single-shot photo-electron trapping. a Charge stability diagram measured around the (1,1)-(0,2) transition line in white and the (0,1) region. b Example trace of a real-time charge sensor current I_sensor measured at point ● in the stability diagram with B = 1 T. The trace starts from the I_sensor blocked at a lower value indicating (1,1) and frequently changes between the low and high values indicating the repeated (1,1)-(0,2) transitions. The two regions indicate the parallel and anti-parallel spin configurations, respectively. c Histogram of the number of events of finding the (1,1) blocked state vs. the state residing time derived from the I_sensor trace measured continuously for minutes. The histogram fits a double-exponential curve with two time constants, τ_slow and τ_fast. These values are used to optimize threshold time for the single-shot spin measurements (see text). d Photon irradiation results at B = 0 T measured at point ★ in the stability diagram. I_sensor in red oscillates due to the repeated (1,1)-(0,2) transitions. The two-electron charge dynamics is observed until one of the two electrons escapes from the DQD. I_sensor in black stays at the low level showing no photo-electron trapping. A small offset of I_sensor observed for t > 0 ms is due to the small photoconductivity of the charge sensor. e Energy spectrum of the photo-electron trapping probability. The laser power is tuned such that ~20 photons reach the QD area per shot for this figure. The heavy-hole peak is found at 1.579 eV, and the light hole peak is expected to be at 1.602 eV from simulation for the 7.3 nm-width quantum well (QW) but not well resolved. Error bars are standard deviations expected from the binomially distributed single-shot results of photo-electron detection