Fig. 3

Single photo-electron spin detection and angular momentum transfer. a Two typical I_sensor traces of photo-electron trapping, indicating down-spin trapping in the upper panel, and up-spin trapping in the lower panel, respectively. b Polarization and field polarity dependence of the blocked probability, reflecting the angular momentum transfer from a single photon to an electron spin. A sinusoidal dependence is observed against the rotation angle θ of polarization from −π/4 to π/4. By reversing the external magnetic field or reversing the polarity of the spin detection axis, we observe a flipped curve. This means that a single photon polarization creates a single fixed electron spin in the dot, following the conversion rule depicted in Fig. 1a. Each data point is derived from the single-shot measurements repeated more than 1000 times. The photo-electron trapping rate averaged over all measurements is 3%. The error bars ~5% are the standard deviation of the binomial distribution for each measurement point. From the fitting to the sinusoidal curve an amplitude of 25 ± 2% (27 ± 5%) and an offset of 45 ± 1% (44 ± 2%) for B = 1.65 T (−1.65 T) are obtained. We used these parameters for fidelity calculation