Efficient and compact quantum network node based on a parabolic mirror on an optical chip

TL;DR

This paper presents a compact, fiber-integrated neutral atom quantum network node using a parabolic mirror, achieving high photon collection efficiency and entanglement fidelity, suitable for scalable quantum networks.

Contribution

The authors demonstrate a novel, cavity-free atom-photon interface with high efficiency and fidelity, compatible with scalable quantum networking architectures.

Findings

Photon collection efficiency of 5% with detection

Atom-photon entanglement fidelity of 0.93 raw, 0.98 corrected

Design is reproducible and compatible with atomic arrays

Abstract

We demonstrate a neutral atom networking node that combines high photon collection efficiency with high atom photon entanglement fidelity in a compact, fiber integrated platform. A parabolic mirror is used both to form the trap and to collect fluorescence from a single rubidium atom, intrinsically mode matching $\sigma$ polarized emitted photons to the fiber and rendering the system largely insensitive to small imperfections or drifts. The core optics consist of millimeter scale components that are pre aligned, rigidly bonded on a monolithic in-vacuum assembly, and interfaced entirely via optical fibers. With this design, we measure an overall photon collection and detection efficiency of $5\%$, from which we infer an overall collection efficiency of $9\%$ after the single--mode fiber coupling. We generate atom photon entangled states with a raw Bell state fidelity of 0.93 and an inferred fidelity of 0.98 after correcting for atom readout errors. The same node design has been realized in two independent setups with comparable performance and is compatible with adding high NA objective lenses to create and control atomic arrays at each node. Our results establish a robust, cavity free neutral atom interface that operates near the limit set by the collection optics numerical aperture and provides a practical building block for scalable quantum network nodes and repeaters.