Fine structure splitting energy correction for single quantum dot via quadrupole potential

Entangled photon sources are crucial for quantum optics, quantum sensing and quantum communication. Semiconductor quantum dots in nanowires have recently emerged as leading candidates to generate entangled photons due to their... [ view full abstract ]

Entangled photon sources are crucial for quantum optics, quantum sensing and quantum communication. Semiconductor quantum dots in nanowires have recently emerged as leading candidates to generate entangled photons due to their high brightness and directional Gaussian emission profile for near-unity fiber coupling. However, the structural asymmetry of the quantum dot leads to a fine-structure splitting (FSS) and severely limits the use of quantum dots as a source of entangled photon pairs with high fidelity. Here, we propose a novel approach for generating a pair of entangled photons from the quantum dot with high fidelity by correcting the spatial asymmetry of the excitonic wave function via application of a quadrupole electrostatic potential. The proposed device architecture and the far field emission profile is presented in Figure 1: Proposed device.

We have performed numerical simulations for the proposed device by Nextnano3 in 2D, which solves the Schrödinger-poison equation self-consistently. In Figure 2, FSS and electron-hole (e-h) overlap is plotted as a function of quadrupole potential, V applied on the proposed device. Our results demonstrate that the spatial asymmetry of the excitonic wave function can be tuned without compromising the spatial overlap between electron and holes. Importantly, the FSS can be tuned to zero, meaning that the excitonic wavefunction is symmetric, even when the electrical gates are misaligned with respect to the quantum dot asymmetry. Finally, we will present the nanofabrication of the first generation of devices and initial results (Figure 3: fabricated device). This work paves the way toward a deterministic source of entangled photons with high fidelity and unprecedented collection efficiency.