A scalable photonic interface for neutral atom arrays using optical microcavities

Neutral-atom arrays are a leading platform for quantum computation. Fault-tolerance will require millions of physical qubits, motivating modular architectures that interconnect many-atom registers. A key element of a fault tolerant distributed processor is an interface that allows for high-rate remote entanglement generation with networking qubits. Here we present a photonic interface based on small-mode-volume fiber Fabry-Perot microcavities and demonstrate its integration with optical-tweezer arrays. The microcavity design supports a strong atom-photon coupling of tens of atoms simultaneously and enables a high-bandwidth photon emission. We demonstrate array-cavity coupling for registers of ≥25 atoms, including simultaneous coupling of six atoms to the same cavity mode with single-atom cooperativity C≈40. Due to the small-mode-volume geometry the cavity mode overlaps only with a single row of atoms at a time. To overcome this limitation and show the compatibility of a microcavity platform with 2D arrays of atoms we implement a "drive-by" protocol in which atoms remain trapped in the optical tweezers as the array is translating through the cavity mode. We couple at least five rows of atoms while maintaining strong coupling regime and reuse the same array for multiple drive-by cycles in a single experimental sequence. We estimate multiplexed 2D array entanglement protocols will lead to at least a 10x spin-photon entanglement rates given realistic switching times between rows and modest array sizes. To complement probabilistic photonic links with deterministic local Rydgerg gates required for the complete distributed computation toolset we are developing microcavity designs with optimal geometries and minimized stray electric fields. These results show key components of a scalable cavity QED interface for modular neutral-atom processors.