Would this be possible without it being able to run novel real-world physics experiments autonomously?
(Note: I am not suggesting we let it do this. Please don't, in fact)
Pharmaceuticals already are…
It could be a good theoretical physicist. Actually it could be a good experimental physicist as well since senior experimental physicists use grad students for the manual labor.
AI could discover candidate novel physics without autonomously operating new physical experiments, and humans or instruments can later independently validate the result. This is analogous to how Einstein developed theories whose predictions were confirmed by experiments and observations only years or decades later.