High efficiency coupling of photon pairs in practice

TL;DR

This paper presents a quantum theoretical model for designing entangled photon sources with high coupling efficiency, achieving over 80% efficiency in various configurations, which is crucial for quantum communication applications.

Contribution

The paper introduces a simple theoretical model enabling the design of high-efficiency photon pair sources, including a novel symmetric coupling efficiency over 80% in non-degenerate configurations.

Findings

Achieved symmetric coupling efficiency >80% in non-degenerate configuration

Demonstrated high efficiency across continuous wave and pulsed regimes

Applicable to various nonlinear crystals

Abstract

Multi-photon and quantum communication experiments such as loophole-free Bell tests and device independent quantum key distribution require entangled photon sources which display high coupling efficiency. In this paper we put forward a simple quantum theoretical model which allows the experimenter to design a source with high pair coupling efficiency. In particular we apply this approach to a situation where high coupling has not been previously obtained: we demonstrate a symmetric coupling efficiency of more than 80% in a highly frequency non-degenerate configuration. Furthermore, we demonstrate this technique in a broad range of configurations, i.e. in continuous wave and pulsed pump regimes, and for different nonlinear crystals.