Nanophotonic quantum interface and transportable entanglement for atom arrays*

Realization of an efficient quantum optical interface for multi-qubit systems is an outstanding challenge in quantum engineering. Using atomic qubits trapped in individually controlled optical tweezers with the ability to move to and from a nanofabricated photonic crystal cavity, we demonstrate a method for interfacing neutral atoms with optical photons. With this cavity QED platform, we show full coherent control, efficient non-demolition readout, and entanglement of atom pairs strongly coupled to the cavity. By encoding the qubits into the magnetically insensitive ground states and utilizing dynamical decoupling, the entangled state is transported away from the cavity and verified in free space. This combination of a compact, integrated optical link and entanglement transport is a step toward quantum networking with neutral atom quantum processors.