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Q: Fachverband Quantenoptik und Photonik

Q 67: Poster – Quantum Information

Q 67.13: Poster

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

Faster, more efficient loading of Yb⁺ and Ba⁺ ions for mixed-species cryogenic trapped ion quantum computers — •Marwan Mohammed^1,2, Michael Johanning², and Christof Wunderlich¹ — ¹Department of Physics, School of Science and Technology, University of Siegen, 57068 Siegen, Germany — ²eleQtron GmbH, 57072 Siegen, Germany

Trapped ion quantum computers (TIQCs) in cryogenic vacuum facilitate both longer lifetimes and reduced motional heating of Coulomb crystals. However, keeping a low heat load typically necessitates pulsed laser ablation for ion loading. Only a small fraction of slow-moving ablated atoms are trappable by surface trap chips, but capturing faster-moving ablated atoms by increasing trap depth would increase the laser cooling time and therefore loading time significantly, whereas using higher pulse fluences to trap more ions risks chip contamination.

To this end, we present improvements to the ion loading process for two cryogenic quantum demonstrators that utilise Yb⁺–Ba⁺ mixed crystals. Two-photon photoionisation schemes shall use autoionizing transitions with larger absorption cross-sections; we will investigate a 531 nm transition for Ba⁺ and use autoionization spectroscopy to discover and characterise suitable Yb⁺ transitions. In addition, we realise a fiber-coupled pulsed ablation laser for more consistent shot-to-shot loading, and investigate a loading scheme using a compact effusive atomic source. Overall, this will yield faster, more efficient ion loading, benefitting both TIQCs of larger ion numbers and trapping of low-abundance ionic species.

Keywords: Trapped ion quantum computing; Cryogenic vacuum; Ion loading; Autoionization