MHz rate and efficient synchronous heralding of single photons at telecom wavelengths

TL;DR

This paper demonstrates a high-rate, efficient source of heralded single photons at telecom wavelengths using SPDC in PPLN crystals, achieving MHz heralding rates and high coupling efficiency for quantum communication applications.

Contribution

The work presents a novel, synchronized single-photon source at telecom wavelengths with MHz heralding rates and optimized coupling efficiency, advancing quantum communication technology.

Findings

Achieved 4.4 MHz heralding rate with 45% efficiency

Heralding efficiency can reach up to 80% with coupling optimization

Group velocity mismatch affects photon spectrum and fiber coupling

Abstract

We report on the realization of a synchronous source of heralded single photons at telecom wavelengths with MHz heralding rates and high heralding efficiency. This source is based on the generation of photon pairs at 810 and 1550 nm via Spontaneous Parametric Down Conversion (SPDC) in a 1 cm periodically poled lithium niobate (PPLN) crystal pumped by a 532 nm pulsed laser. As high rates are fundamental for multi-photon experiments, we show that single telecom photons can be announced at 4.4MHz rate with 45% heralding efficiency. When we focus only on the optimization of the coupling of the heralded photon, the heralding efficiency can be increased up to 80%. Furthermore, we experimentally observe that group velocity mismatch inside long crystals pumped in a pulsed mode affects the spectrum of the emitted photons and their fibre coupling efficiency. The length of the crystal in this source has been chosen as a trade off between high brightness and high coupling efficiency.