Development of neutral atom-photon quantum interface with a nanofiber cavity

A cavity-based atom-photon interface is a promising approach toward modular and scalable quantum computing. Indeed, it combines the long coherence time of neutral-atom qubits and the spatial reach of flying photonic qubits. However, the latter quality can be optimally exploited for connectivity only when the photons are efficiently guided in fiber-modes. In this context, we present our on-going development of a nanofiber cavity QED platform for deterministic gate operations between atomic and photonic qubits. Our cavity is an all-fiber device composed of two Bragg gratings serving as end mirrors and a nanofiber region that is narrowed to subwavelength radius. There, the evanescent field couples the atoms and the cavity mode, allowing efficient in- and out-coupling of the atomic qubit to the fiber mode. The atom-photon gate operation is implemented on single Cs atom trapped in the vicinity of the nanofiber cavity by an optical tweezer, where the tweezer captures the atoms from a neighboring magneto optical trap (MOT). However, to mitigate cavity quality degradation caused by Cs deposition onto the nanofiber, we minimize the overall Cs vapor pressure near the nanofiber. Thus, the MOT is loaded from a transversely cooled atomic beam, generated in a 2D MOT + push beam configuration. Moreover, we describe an imaging system implemented by a two-photon atom excitation process that eliminates parasitic light scattered by the fiber. Finally, we describe our roadmap towards a telecom-band nanofiber cavity system with ytterbium atoms, which promises increased coherence time, gate fidelity, and connectivity.