Multi-partite entanglement in extreme nanophotonic cavities

TL;DR

This paper presents nanobeam photonic crystal cavities with ultra-high quality factors and sub-wavelength confinement, enabling efficient atom-photon entanglement and scalable quantum network components.

Contribution

Introduction of nanobeam photonic crystal cavities with extreme quality factors and tailored for ultracold atom entanglement at 780 nm.

Findings

Achieved quality factors around 10^7.

Demonstrated coherent entanglement between atoms.

Platforms are scalable for large quantum networks.

Abstract

Multi-partite entanglement is fundamental to emerging quantum technologies such as quantum networks, which ultimately require devices with strong light-matter interactions and long coherence times. Here, we introduce nanobeam photonic crystal cavities combining both extreme quality factors ($\sim10^{7}$) with sub-wavelength field confinement to reach unprecedented light-matter interactions. Operating at $780$ nm, our devices are tailored for efficient coupling and entanglement with ultracold $^{87}$Rb atoms, a key ingredient in quantum networks due to their hyperfine structure. Our new designs also facilitate the precise optical trapping of atoms, and we demonstrate coherent entanglement generation between them, that is remarkably resilient to atomic displacements. These platforms can be easily scaled-up to extremely large quantum networks, for distributed quantum computing and future light-based quantum technologies.