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Quantum-Enhanced Second Harmonic Generation pumped by Parametric Down Conversion Beyond the Photon Pairs Regime

T. Dickinson, Ivi Afxenti, Giedre Astrauskaite, Lennart Hirsch, Samuel Nerenberg, O. Jedrkiewicz, D. Faccio, C. Müllenbroich, A. Gatti, M. Clerici, Lucia Caspani

Published Jan 1, 2025• 0 citations
Publisher

Abstract

We demonstrate quantum-enhanced second harmonic generation driven by highly multimode parametric down conversion radiation, showing efficiency exceeding that of classical illumination up to intensities ten times the traditional quantum-classical boundary.
DOI
10.1364/nlo.2025.m3a.5

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Two-photon processes are crucial in applications like microscopy and microfabrication, but their low cross section requires intense illumination and limits, e.g., the penetration depth in nonlinear microscopy. Entangled states have been proposed to enhance the efficiency of two-photon interactions and have shown effectiveness at low intensities. This quantum enhancement is generally believed to be lost at high intensities, for more than one photon per mode, raising doubts about its usefulness. We explored experimentally and theoretically two-photon processes driven by entangled photons at intensities beyond this threshold and compared the results with the classical case. We found that a quantum advantage can still be observed at nearly one order of magnitude higher intensities than previously assumed. Our findings show a potential path for exploiting quantum-enhanced two-photon processes in practical applications.