Hedge fund Citadel has strengthened its North American compute team with the hire of Christopher Johnston, formerly head of platform Linux engineering at rival multi-strategy major Millennium Management, according to a report by eFinancial Careers.

Johnston joins as head of North America Compute, bringing experience from high-frequency trading firms Virtu Financial and Jump Trading, as well as a background in banking. The hire comes amid Citadel’s ongoing push to enhance its computing architecture for quantitative research and AI applications, even as CEO Ken Griffin recently said generative AI has yet to generate meaningful alpha.

The move follows the departure of long-serving Citadel compute veteran Scott Donovan, who left for Optiver last month.