Interfacing transitions of different alkali atoms and telecom bands using one narrowband photon pair source

TL;DR

This paper presents a tunable, narrowband photon pair source based on whispering-gallery mode resonators that can be matched to alkali atomic transitions, facilitating quantum information applications.

Contribution

The authors developed a novel wavelength tuning mechanism enabling coarse and fine adjustments to match cesium or rubidium transitions in a photon pair source.

Findings

Successful coupling to alkali atomic transitions demonstrated

Achieved continuous fine-tuning of photon wavelength

Enhanced compatibility with narrow-band quantum systems

Abstract

Quantum information technology strongly relies on coupling of optical photons with narrowband quantum systems, such as quantum dots, color centers, and atomic systems. This coupling requires matching the optical wavelength and bandwidth to the desired system, which presents a considerable problem for most available sources of quantum light. Here we demonstrate coupling of alkali dipole transitions with a tunable source of photon pairs. Our source is based on spontaneous parametric down-conversion in a triply-resonant whispering-gallery mode resonator. For this, we have developed novel wavelength tuning mechanisms, which allow for a coarse tuning to either cesium or rubidium wavelength with subsequent continuous fine-tuning to the desired transition. As a demonstration of the functionality of the source, we performed a heralded single photon measurement of the atomic decay. We present a major advance in controlling the spontaneous down-conversion process, which makes our bright source of single photons now compatible with a plethora of narrow-band resonant systems.