But several of these companies are customers of California-based Nvidia, a major maker of graphics processing chips heavily used by the world's artificial intelligence firms. The blacklisted firms include SenseTime, which creates machine vision technology, and Megvii and Hikvision, which sell facial recognition technology. "These firms' operations have required good relationships with Silicon Valley, including big chipmakers like Nvidia ," said Rui Zhong, a program assistant for the Kissinger Institute on China and the United States at the Wilson Center. "America's surveillance ties to the Chinese state operating in Xinjiang ranges from cameras and imaging technology to biodata processing." Nvidia declined to comment on the effect of the sanctions on its operations. The issue of how to deal with technology transfers between the United States and China is one that has been simmering for years.