Figure 1

(a) Bias dependent PL intensity map of a single InAs SAQD, where $X^{n\pm }$ denotes the charged exciton with $n$ excess electrons ($-$) or holes ($+$). (b) Trion energy level diagram at zero magnetic field. (c) Polarization dependent VM spectra of a singly charged QD at zero magnetic field. $L$, $R$, $V$, and $H$ denote left circular, right circular, vertical, and horizontal polarization, respectively. Curves are the fittings of the data.Reuse & Permissions

Figure 2

(a) Bias dependent VM absorption map of a singly charged SAQD at a magnetic field of 0.88 T. The laser is 45° polarized. Voltage region I shows all four trion transitions. Spin state preparation is achieved in Voltage range II. (b) Energy level diagram of a trion. The gate voltage is set at 0.19 V for plots (c), (d), and (e). (c) Polarization dependent VM spectra of a singly charged QD at magnetic fields 0.88 T. The black curves are the fittings. (d) $3d$ plot of the trion evolution with various magnetic fields. The laser is 45° polarized. The data are inverted for clarity. (e) The electron (black dots) and hole (orange dots) Zeeman splitting as a function of the magnetic fields.Reuse & Permissions

Figure 3

Demonstration of the spin state preparation in $|x+>$ ($|x->$) state at magnetic field 1.32 T and gate voltage 0.12 V. The scanning laser is 45° polarized and the PIB is vertically polarized. (a) and (b) [(c) and (d)]. The PIB is resonant with the transition $V1$ ($V2$) while probing the transitions $H2$ and $V2$ ($H1$ and $V1$). (e) One beam absorption spectrum of the trion state in the absence of the PIB. The absorption of transitions $V1$ and $V2$ are strongly suppressed due to the optical pumping effect. Since the degeneracy of transitions $H1$ and $H2$ are lifted by increasing the magnetic field to 1.32 T, the central peak is also suppressed.Reuse & Permissions