Integrated photonics for photon mediated entanglement generation and sub-Doppler cooling*

Trapped-ion platforms are being developed for use in applications such as atomic clocks, quantum sensing, quantum networking and quantum information processing. For all these applications, entanglement generation between spatially separated ions is a resource that is either needed or beneficial for their functionality. Additionally, many applications require ions to be cooled to their motional ground state, a procedure that often has a large time overhead. To address both challenges, integrated photonics can be used to generate the optical circuits needed for remote entanglement generation and high bandwidth sub-doppler cooling techniques.

Previous demonstrations of photon mediated entanglement used free-space optics to collect and entangle photons emitted from the trapped ions. Here we present tests of a trap-integrated diffractive grating which is used to collect ion fluorescence and perform state detection. Additionally, we discuss how additional integrated elements can be used with these collection gratings to perform photon mediated entanglement between spatially separated trapped ions. Further we present tests of emission grating pairs that have been designed to generate optical polarization gradients which can be used for sub-Doppler cooling. Integrated photonic circuits offer an avenue for scaling up the number of entangled ion nodes as well as addressing difficulties in efficiently cooling larger Coulomb crystals to their motional ground state.