DeepSeek, a Chinese artificial intelligence (AI) start-up, is sending shock waves through the U.S. tech sector by demonstrating its latest AI assistant, which achieves performance comparable to or even surpassing some of the world's best chatbots.

Leading the swing were Apple and Nvidia, both Silicon Valley giants with significant dealings in China, as shares of Apple went from as much as a 4% morning gain to a 2% daily loss by late afternoon, and Nvidia stock turned what was as much as a 3% gain to a 3% daily drop.