Integrated and fiber-coupled imaging system for the addressing of single ions

In trapped-ion-based quantum computing, logic gates are performed by laser addressing ions with a specific wavelength to manipulate its quantum state. We present a trap-integrated addressing unit that is ultra-high vacuum compatible and quasi-monolithically bonded onto the trap substrate. Our setup is based on a quadrupole trap for containing a chain of ten calcium ion. A fiber-coupled aluminum oxide waveguide chip emits ten addressing beams at 405 nm, that are imaged by a micro-optical lens stack onto the ion trap axis. The setup allows to address each ion individually and in parallel. Imaging transmission losses are below 2 dB with an ion-addressing spot diameter of 1 µm at 1/e^2 intensity and a Strehl ratio above 0.9 for all ten beams. With an inner minimum ion spacing of 5 µm and a total chain length of approximately 60 µm, the addressing beam crosstalk ratio is less than one percent.