Ultraprecise fiber-optical elements for integration with neutral atom arrays

Recent advances in modular quantum computing with neutral atoms coupled to micro-cavities [1] underscore the need for highly precise micro-optical elements that can boost remote entanglement generation rates and enable scalable architectures. Here we report nanofabrication and characterization of fiber-integrated micro-optical elements engineered for neutral-atom quantum information processing modules. Using focused-ion beam (FIB) milling, we fabricate micro-concave, convex, axicon, and spiral structures directly on single-mode fiber facets. Structural precision is quantified via atomic force microscopy (AFM), revealing better than 10 nm sphericity across more than 70% of the micro-concave elements. Optical characterization of the concave and convex structures demonstrates focal lengths exceeding 200 microns, well suited for cavity QED integration with ultracold atoms. Our approach constitutes a powerful alternative to the widely used fiber machining with pulsed CO2 lasers and opens new possibilities for highly flexible fiber-integrated optical components for ultracold atoms.

[1] B. Grinkemeyer et al., “Error-detected quantum operations with neutral atoms mediated by an optical cavity,” Science 387, 1301–1305 (2025).