Official Google Blog post also has some background info:

AlphaGo: using machine learning to master the ancient game of Go

https://googleblog.blogspot.com/2016/01/alphago-machine-lear...

Interesting that DeepMind was using Google Cloud for compute. I imagine that the MCTS expansion can become massive. Any chance DeepMind may publish some of the internals about how many instances were used, how computation was distributed, any packages or frameworks used, etc.

And congrats on achieving this impressive AI milestone!