A.I. Expert at Baidu, Andrew Ng, Resigns From Chinese Search Giant

The company now has more than 1,300 employees dedicated to A.I. In a signal of just how critical the efforts are to the company, it said in January that it had hired Qi Lu, a former executive at Microsoft and an A.I. specialist, to become the chief operating officer. Mr. Ng's announcement comes after the technology executive Hugo Barra left Xiaomi, a Chinese phone maker and e-commerce company, for Facebook. Mr. Ng and Mr. Barra were viewed as part of a nascent trend of Silicon Valley executives jumping to well-funded Chinese internet companies. They seemed to represent a new era of closer ties, and competition, between America's tech giants and China's. The resignations underline how that trend never materialized.