Sébastien Bubeck, a machine learning researcher at Microsoft, woke up one night last September thinking about artificial intelligence—and unicorns. 

Bubeck had recently gotten early access to GPT-4, a powerful text generation algorithm from OpenAI and an upgrade to the machine learning model at the heart of the wildly popular chatbot ChatGPT. Bubeck was part of a team working to integrate the new AI system into Microsoft’s Bing search engine. But he and his colleagues kept marveling at how different GPT-4 seemed from anything they’d…