Amplification of cascaded downconversion by reusing photons with a switchable cavity

TL;DR

This paper proposes a scheme to enhance triplet photon production in cascaded down-conversion by reusing photons with a switchable cavity, supported by a theoretical model and experimental validation, advancing quantum communication technologies.

Contribution

It introduces a novel method using a switchable cavity and delay loop to amplify triplet photon rates in cascaded down-conversion processes.

Findings

Confirmed increased triplet detection rates experimentally

Theoretical model accurately predicts amplification

Potential for improved quantum communication applications

Abstract

The ability to efficiently produce and manipulate nonclassical states of light is a critical requirement for the development of quantum optical technologies. In recent years, experiments have demonstrated that cascaded spontaneous parametric down-conversion is a promising approach to implement photon precertification, providing a way to overcome photon transmission losses for quantum communication, as well as to directly produce entangled three-photon states and heralded Bell pairs. However, the low efficiency of this process has so far limited its applicability beyond basic experiments. Here, we propose a scheme to amplify triplet production rates by using a fast switch and a delay loop to reuse photons that fail to convert on the first pass through the cascade's second nonlinear crystal. We construct a theoretical model to predict amplification rates and verify them in an experimental implementation. Our proof-of-concept device increases the rate of detected photon triplets as predicted, demonstrating that the method has the potential to dramatically improve the usefulness of cascaded down-conversion for device-independent quantum communication and entangled state generation.