Highly entangled-photon pairs generated from the biexciton cascade transition in a quantum dot-metal nanoparticle hybrid system

TL;DR

This paper theoretically investigates how a quantum dot near a metal nanoparticle can generate highly entangled photon pairs through the biexciton cascade, with entanglement influenced by system geometry.

Contribution

It introduces a hybrid quantum dot-metal nanoparticle system that enhances photon entanglement without requiring strong coupling, overcoming natural exciton splitting.

Findings

Photon pairs are degenerate in energy over a broad spectral window.

Entanglement degree depends on nanoparticle radius and quantum dot distance.

System modifies photon entanglement even without strong emitter-nanoparticle coupling.

Abstract

The entanglement between photon pairs generated from the biexciton cascade transition in a semi- conductor quantum dot located in the vicinity of a metal nanoparticle is theoretically investigated. In the model scheme, the biexciton-exciton and exciton-ground state transitions are assumed to be coupled to two principal plasmon modes of orthogonal polarizations. For a broad spectral window, because the horizontal and vertical spectra are overlapped, the biexciton and exciton photons are degenerate in energy. This allows us to overcome the natural splitting between the intermediate exciton states. Moreover, the degree of entanglement depends on the geometrical parameters of the system. i.e., the radius of the metal nanoparticle and the distance between the quantum dot and the nanoparticle. The results reveal that such a hybrid system profoundly modifies the photon entanglement even in the absence of strong coupling between the emitter and the metal nanosphere.