Investigations of the benefits and challenges of using integrated optics for trapped-ion quantum logic

Trapped ion qubits have proven to be an excellent platform for quantum information processing due to their ability to be decoupled from the environment, enabling long coherence times and high-fidelity state preparation, gate operation, and readout. One of the open questions in quantum computing with trapped ions is how best to build up a practical quantum system. One promising approach is based on microfabricated ion trap chips with integrated photonic waveguides and grating out-couplers. Here, we demonstrate single and two qubit gates with $^{88}$Sr$^+$ trapped ion qubits using such a trap chip. The gates are performed with a 674 nm beam that is either coupled into the waveguides or is delivered via free space. We compare the two delivery methods to demonstrate progress towards a robust quantum logic, and we present challenges that still need to be overcome.