# Generating single longitudinal mode entangled photons in telecom band via a submillimeter monolithic cavity

## TL;DR

This paper introduces a compact, high-quality entangled photon source in the telecom band using a submillimeter monolithic cavity, simplifying the setup for quantum communication applications.

## Contribution

The authors demonstrate a novel, simple method to generate single longitudinal mode entangled photons in a compact cavity, improving upon traditional free-space cavity systems.

## Key findings

- High coincidence to accidental ratio indicating high photon quality
- Successful measurement of two-photon interference fringes
- Compact cavity design enhances practicality for quantum communication

## Abstract

A high-quality, compact, and narrow-bandwidth entangled photon source (EPS) is indispensable for realization of many quantum communication protocols. Usually, a free space cavity containing a nonlinear crystal is used to generate a narrow bandwidth EPS through spontaneous parametric down-conversion (SPDC). One major drawback is that this occupies a large space and requires complex optical and electrical control systems. Here we present a simple and compact method to generate a single-longitudinal-mode time-energy EPS via type II SPDC in a submillimeter Fabry-Perot cavity. We characterize the quality of the EPS by measuring the coincidence to accidental coincidence ratio, the two-photon time cross-correlation function and the two-photon interference fringes. All measured results clearly demonstrate that the developed source is of high quality when compared with EPSs generated using other configurations. We believe this source is very promising for applications in the quantum communication field.

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Source: https://tomesphere.com/paper/1906.05104