Artificial intelligence expert Russ Salakhutdinov has joined Apple as its director of AI research. The Carnegie Mellon professor tweeted Monday that he was "excited" about the new position, and indicated that the company is looking for more AI engineers.

Salakhutdinov's research is in the field of "statistical machine learning," according to his CMU biography. He is no stranger to the tech industry, having previously served as a Microsoft Research Faculty Fellow; he also picked up awards from Google and Nvidia.

Apple's AI expert hiring spree comes as the company faces its archrivals Google and Microsoft in an ever more lucrative market for machine learning. Siri, its main artificial intelligence product, graduated from the iPhone to the Mac this year with the release of macOS Sierra, and now also boasts an API for third-party app integrations. Google's Assistant and Microsoft's Cortana have followed similar trajectories.

Apple also must take on Facebook and Amazon, whose Alexa and Facebook Messenger platforms have quickly become the go-to products for home automation and chatbots, respectively.

On Twitter, Salakhutdinov linked to an Oct. 13 posting on Apple's careers website seeking machine learning research scientists with PhDs "from the realms of deep learning, reinforcement learning, unsupervised learning, and computer perception."

Cupertino isn't the only Silicon Valley giant interested in Carnegie Mellon's computer scientists. Uber recently launched its self-driving car beta in Pittsburgh, the university's backyard. The location was chosen partly for its challenging geography and partly because dozens of Uber poached dozens of autonomous driving engineers from Carnegie Mellon in 2015.