A novel single-crystal & single-pass source for polarisation- and colour-entangled photon pairs

TL;DR

This paper introduces a compact, efficient photon pair source that generates polarization- and color-entangled photons using a novel phase-matching technique in a single crystal, advancing quantum information technology.

Contribution

The paper presents a new phase-matching method in periodically poled KTP crystals enabling simultaneous dual downconversion processes for entangled photon generation.

Findings

Produces maximally entangled photon pairs with high brightness

Operates with a single unidirectionally pumped crystal

Offers a compact and luminous entanglement source

Abstract

We demonstrate a new generation mechanism for polarisation- and colour-entangled photon pairs. In our approach we tailor the phase-matching of a periodically poled KTP crystal such that two downconversion processes take place simultaneously. Relying on this effect, our source emits entangled bipartite photon states, emerging intrinsically from a single, unidirectionally pumped crystal with uniform poling period. Its property of being maximally compact and luminous at the same time makes our source unique compared to existing photon-entanglement sources and is therefore of high practical significance in quantum information experiments.