Mainz 2026 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 67: Poster – Quantum Information

Q 67.14: Poster

Thursday, March 5, 2026, 17:00–19:00, Philo 2. OG

A cryo-compatible optical system for addressing and achromatic imaging of trapped Yb⁺ and Ba⁺ ions — •Ernst Alfred Hackler, Daniel Busch, Kunal Kumbhar, Marwan Mohammed, Patrick H. Huber, Dorna Niroomand, and Christof Wunderlich — Walter-Flex-Straße 3, 57072 Siegen

To interface with the ions in a cryogenic ion trap quantum computer, we need to guide different laser wavelengths to trapped ions inside a cryogenic vacuum chamber and image the ions precisely and with high collection efficiencies.
Firstly, we have simulated and constructed a modular, compact overlapping unit comprising dichroic mirrors in order to produce a combined, collimated laser beam containing all the necessary wavelengths for state detection and preparation of Yb⁺ and Ba⁺ ions. By using off-the-shelf parts and an optimization algorithm for determining the optimal mirror choice, we achieve overlapping of 8 wavelengths used for Yb⁺ and Ba⁺ from 369–935 nm. The laser intensities are well-above the saturation intensities of the ions at the position of a 10-ion chain.
Secondly, we developed and built a system for simultaneous imaging of both ion species, without chromaticity errors. A reflective objective lens, originally designed at Leibniz Universität Hannover, allows for in-vacuum, achromatic fluorescence imaging closer to the ions’ position, increasing the light collection efficiency. We were able to image components inside the cryostat and demonstrate the system’s general behaviour.

Keywords: Optics; Imaging; Ion trap; Quantum computing