Estimation of the rate of entangled-photon-pair interaction with metallic nanoparticles based on classical-light second-harmonic generation measurements

Entangled-photon-pair interaction (EPPI) with matter is a key element in many suggested quantum-light applications and an enhancement of this interaction is of great importance. In this paper, we suggest and investigate the use of metallic nanoparticles (MNPs), with their exceptional capability of light matter coupling at their localized surface plasmon resonance, for a potential enhancement of EPPI. We specifically investigate second-harmonic generation and theoretically estimate the rate of EPPI with MNPs using measurements with classical-light. We perform a simple measurement based on approximating the optical-setup factor G, of hyper-Rayleigh scattering. Experimental results, obtained for solutions of silver NPs (SNPs) with different densities, show a hyperpolarizability of about 10-24[esu]. The results indicate that the use of SNPs can indeed be advantageous for EPPI, with an estimated three orders-of magnitude enhancement of the hyperpolarizability, relative to the best organic molecules. However, we show that further optimization of the SNPs should be carried out to enlarge their EPPI crosssection even more.