Pure single photon generation by type-I PDC with backward-wave amplification

TL;DR

This paper proposes a novel method for generating pure heralded single photons using backward-wave parametric downconversion in periodically-poled waveguides, enabling broad-spectrum applications with minimal spectral correlations.

Contribution

It introduces a counter-propagating photon pair generation technique that reduces spectral correlations, expanding the range of usable materials for pure single photon sources.

Findings

Minimal spectral correlations in generated photon pairs

Potential to use materials like PPLN previously considered unsuitable

Broad frequency range for heralded single photon generation

Abstract

We explore a promising method of generating pure heralded single photons. Our approach is based on parametric downconversion in a periodically-poled waveguide. However, unlike conventional downconversion sources, the photon pairs are counter-propagating: one travels with the pump beam in the forward direction while the other is backpropagating towards the laser source. Our calculations reveal that these downconverted two-photon states carry minimal spectral correlations within each photon-pair. This approach offers the possibility to employ a new range of downconversion processes and materials like PPLN (previously considered unsuitable due to their unfavorable phasematching properties) to herald pure single photons over a broad frequency range.