Proposed Scheme to Generate Bright Entangled Photon Pairs by Application of a Quadrupole Field to a Single Quantum Dot

TL;DR

This paper proposes a novel method using a quadrupole electrostatic potential to generate high-fidelity, efficiently collected entangled photon pairs from quantum dots by correcting asymmetries and eliminating fine-structure splitting.

Contribution

It introduces a quadrupole electric field technique to improve entangled photon generation from quantum dots, overcoming asymmetry and collection efficiency issues.

Findings

Quadrupole electric field corrects quantum dot asymmetry.

Erases fine-structure splitting without reducing electron-hole overlap.

Compatible with nanophotonic structures for deterministic photon sources.

Abstract

Entangled photon sources are crucial for quantum optics, quantum sensing and quantum communication. Semiconductor quantum dots generate on-demand entangled photon pairs via the biexciton-exciton cascade. However, the pair of photons are emitted isotropically in all directions, thus limiting the collection efficiency to a fraction of a percent. Moreover, strain and structural asymmetry in quantum dots lift the degeneracy of the intermediate exciton states in the cascade, thus degrading the measured entanglement fidelity. Here, we propose an approach for generating a pair of entangled photons from a semiconductor quantum dot by application of a quadrupole electrostatic potential. We show that the quadrupole electric field corrects for the spatial asymmetry of the excitonic wavefunction for any quantum dot dipole orientation and fully erases the fine-structure splitting without compromising the spatial overlap between electrons and holes. Our approach is compatible with nanophotonic structures such as microcavities and nanowires, thus paving the way towards a deterministic source of entangled photons with high fidelity and collection efficiency.