Quantum Nonlinear Optics with a Germanium-Vacancy Color Center in a Nanoscale Diamond Waveguide

TL;DR

This paper presents a quantum nanophotonics platform using germanium-vacancy centers in diamond waveguides, demonstrating efficient photon interaction and single-photon nonlinear effects without cavities.

Contribution

It introduces a cavity-free, fiber-coupled diamond nanophotonic system with GeV centers exhibiting high quantum efficiency and nonlinear behavior at the single-photon level.

Findings

GeV centers have high quantum efficiency in nanophotonic structures

Single GeV reduces waveguide transmission by 18% on resonance

System exhibits nonlinearity at the single-photon level

Abstract

We demonstrate a quantum nanophotonics platform based on germanium-vacancy (GeV) color centers in fiber-coupled diamond nanophotonic waveguides. We show that GeV optical transitions have a high quantum efficiency and are nearly lifetime-broadened in such nanophotonic structures. These properties yield an efficient interface between waveguide photons and a single GeV without the use of a cavity or slow-light waveguide. As a result, a single GeV center reduces waveguide transmission by $18 \pm 1\%$ on resonance in a single pass. We use a nanophotonic interferometer to perform homodyne detection of GeV resonance fluorescence. By probing the photon statistics of the output field, we demonstrate that the GeV-waveguide system is nonlinear at the single-photon level.