Long-distance cascaded fluorescence of cold Cesium atoms coupled to an optical nanofiber

TL;DR

This paper reports the first experimental demonstration of long-distance cascaded resonance fluorescence between two independent cold Cesium atom ensembles coupled via an optical nanofiber, advancing quantum networking capabilities.

Contribution

It introduces the first realization of 64-meter long-distance cascaded fluorescence between independent atom ensembles, with a simple model explaining non-Markovian dynamics.

Findings

Cascaded fluorescence spectrum is broadened and blue-shifted.

Achieved the longest-distance one-way atom-photon interface to date.

Model reproduces power broadening and flux ratios.

Abstract

We demonstrate the first experimental realization of cascaded resonance fluorescence over a 64-meter propagation delay time between two spatially and temporally independent ensembles of laser-cooled Cesium atoms coupled to an optical nanofiber. Spontaneously emitted photons from a strongly driven first ensemble are guided through a standard fiber, reflected by a fiber Bragg grating mirror, and interact with a second ensemble, producing a unidirectional two-node cascaded system. The cascaded fluorescence spectrum is broadened and blue-shifted relative to the original fluorescence spectrum. Our simple model reproduces the power broadening and the cascaded fluorescence spectrum, as well as the ratio of cascaded to original photon flux, giving insight into non-Markovian dynamics. Our results establish the longest-distance one-way cascaded atom-photon interface reported to date, providing a stepping stone towards a fiber-based platform for quantum networking.