Entangled photons from a strongly coupled quantum dot-cavity system

TL;DR

This paper theoretically investigates a strongly coupled quantum dot-cavity system as a source of entangled photon pairs, analyzing the effects of system parameters on entanglement quality and emission rates, with implications for quantum communication.

Contribution

It provides a detailed theoretical analysis of realistic quantum dot-cavity systems, including oscillator strength effects and multi-resonance tuning for high entanglement and fast photon emission.

Findings

High entanglement requires independent cavity resonance adjustment.

Strong coupling can enable THz-range emission rates.

Complex tuning and efficiency loss are challenges for practical implementation.

Abstract

A quantum dot strongly coupled to a photonic crystal has been recently proposed as a source of entangled photon pairs [R. Johne et al., Phys. Rev. Lett. 100, 240404 (2008)]. The biexction decay via intermediate polariton states can be used to overcome the natural splitting between the exciton states coupled to the horizontally and vertically polarized light modes, so that high degrees of entanglement can be expected. We investigate theoretically the features of realistic dot-cavity systems, including the effect of the different oscillator strength of excitons resonances coupled to the different polarizations of light. We show that in this case, an independent adjustment of the cavity resonances is needed in order to keep a high entanglement degree. We also consider the case when the biexciton-exciton transition is also strongly coupled to a cavity mode. We show that a very fast emission rate can be achieved allowing the repetition rates in the THz range. Such fast emission should however be paid for by a very complex tuning of the many strongly coupled resonances involved and by a loss of quantum efficiency. Altogether a strongly coupled dot-cavity system seems to be very promising as a source of entangled photon pairs.