The program invites two dozen people, with varying backgrounds in ML
... "with varying backgrounds in ML" -- does that mean that relative beginners have a chance of being accepted?
(I have a personal stake in this! I'm an academic researcher who is getting into ML and working on legal applications, and I'd totally apply for this if I thought you didn't have to basically be Andrew Ng to get in...)
An experienced machine learning researcher like Andrew Ng would probably not join the team as a Brain resident. We hire experienced machine learning researchers and engineers all the time (see https://careers.google.com/jobs#t=sq&q=j&li=20&l=false&jlo=e... ) and the residency program is probably not appropriate for people who are already experts. It is a program designed to help people become experts in machine learning.
For residents we look for some programming ability, mathematical ability, and machine learning knowledge. If an applicant knows absolutely nothing about machine learning, it would be strange (why apply?). We accept people who are not machine learning experts, but we want to be sure that people know enough about machine learning to be making an informed choice about trying to become machine learning researchers. Applicants need to have enough exposure to the field to have some idea of what they are getting into and have the necessary self-knowledge to be passionate about machine learning research.
You can see profiles of a few of the first cohort of residents here: https://research.google.com/teams/brain/residency/
See the old job posting which should hopefully explain the qualifications: https://careers.google.com/jobs#!t=jo&jid=/google/google-bra...
I haven't met the other residents yet (the program doesn't start until mid-July), but based on a few online interactions and meeting some of them at the interviews it seems that a fair number are undergraduates or grad students with some research experience in ML or computer vision. Others seem to have backgrounds more similar to mine, i.e., they were researchers in physics or neuroscience or something and are transitioning to ML.