Spin-Photon Entangling Diode

We propose a semiconductor device that can electrically generate entangled electron spin-photon states, providing a building block for entanglement of distant spins. The device consists of a $p\mathrm{\text{−}}i\mathrm{\text{−}}n$ diode structure that incorporates a coupled double quantum dot. We show that electronic control of the diode bias and local gating allow for the generation of single photons that are entangled with a robust quantum memory based on the electron spins. Practical performance of this approach to controlled spin-photon entanglement is analyzed.

Figure 1

Diode structure, charge stability diagram, and decay paths. (a) The device consists of a double quantum dot within the intrinsic region of a $p\mathrm{\text{−}}i\mathrm{\text{−}}n$ diode structure. A schematic band-edge diagram is shown below. The left hole state (gray) is assumed to be energetically out of reach. (b) The stable charge configuration of the double quantum dot as a function of the bias $V$ and the local gate $F$. The scale bar indicates the total number of charges, while the labeling ($n$, $m$) corresponds to the number of electrons on the left ($n$) and right ($m$) dot, replaced by $X^{-}$ for dots containing a negatively charged exciton consisting of two electrons and a hole. As discussed in the text, the charging sequence indicated by arrows preferentially initializes the dots in the state $|1\uparrow ,X_{S,\Downarrow }^{-}⟩$. (c) Initial and final states for excitonic recombination together with the polarization of the emitted photon. The desired decay processes (shown in black) are selected by filtering ${\sigma }_{-}$ polarization.

Figure 2

Beam splitter setup and entanglement fidelity. (a) Photon interference leading to entanglement between two devices. The entanglement fidelity may be reduced due to different arrival times $\tau$ at the beam splitter, mismatch $\delta \omega$ between energy splittings in the two devices, and incorrect spin initialization (not indicated). (b) Entanglement fidelity $\mathcal{F}$ as function of temperature $T$ and energy mismatch $\delta \omega$. For the calculations, we have used $\gamma \times \overline{\tau }=0.03$. In the white region, $\mathcal{F}>0.9$.