High-Fidelity and Ultrafast Initialization of a Hole Spin Bound to a Te Isoelectronic Center in ZnSe

We demonstrate the optical initialization of a hole-spin qubit bound to an isoelectronic center (IC) formed by a pair of Te impurities in ZnSe, an impurity-host system providing high optical homogeneity, large electric dipole moments, and potentially advantageous coherence times. The initialization scheme is based on the spin-preserving tunneling of a resonantly excited donor-bound exciton to a positively charged Te IC, thus forming a positive trion. The radiative decay of the trion within less than 50 ps leaves a heavy hole in a well-defined polarization-controlled spin state. The initialization fidelity exceeds 98.5% for an initialization time of less than 150 ps.

Figure 1

(a) Time-integrated microphotoluminescence spectrum of the sample studied in this work reveals the presence of three distinct Te dyads preferentially binding neutral excitons ($X_0$), biexciton ($X{X}_0$), and positive trions ($X^{+}$). (b) and (c) Schematic diagrams of the selection rules associated to trion emission at $B=0$ and 5 T in a Faraday configuration. $\sigma$ ($\pi$) represent circularly (linearly) polarized transitions, and solid (empty) circles represent electrons (holes). (d) and (e) Trion photoluminescence intensity as a function of energy and polarization of the emission at $B=0$ and 5 T, respectively.

Figure 2

Time-resolved photoluminescence of trions bound to dyad 1 presented in panel (a) of Fig. 2 for ${\sigma }^{+}$ (a)–(c) and ${\sigma }^{-}$ (d) excitations tuned (a) to the $D\text{−}{X}^0$ band, (b) to the HH band edge, and (c),(d) far above the LH band edge but below the spin-orbit band edge. The blue (red) curves show the emission intensity under copolarized (cross-polarized) excitation and detection. (e) The degree of polarization for dyads 1 (black) and 2 (red) is presented as a function of the excitation energy. The horizontal dashed line indicates the degree of polarization of the emission for an excitation energy 250 meV above the ZnSe band gap. (f) Decay times of trion emission for co- (blue squares) and cross-polarized (red circles) configurations as a function of the excitation energy for dyad 1. The dashed line indicates the upper bound for the radiative decay time of trion states ($<50\mathrm{ps}$).