I am sure that we can say “get in touch with someone”, to mean figuratively that we are in good contact. Can I go further to use it more figuratively, e.g., to say that “my brother is not in touch with reality”, to mean that he is out of step with the reality? Reality may be an analogue of a person, but how about knowledge? Can I say “professor xx in China is in touch with the world’s most advanced researches in the field of xx”, or “this course will put xx in touch with the most advanced… ?
All four of the OP's statements—
get in touch with someone
my brother is not in touch with reality
professor xx in China is in touch with the world’s most advanced research in the field of xx
this course will put xx in touch with the most advanced…
—would be readily understood by most English speakers as indicating a close physical or intellectual connection between the person who is "in touch" and the person or thing that he or she is in touch with. Nevertheless, the specific sense of the figurative language in some cases may differ. For example, "get in touch with someone" means essentially
communicate with someone—either in person or by phone, email, or another form of longer-distance communication.
In contrast, "my brother is not in touch with reality" means something like
my brother's behavior and thinking are not firmly grounded in good sense and a sound appreciation of everyday reality.
And "professor xx in China is in touch with the world’s most advanced research in the field of xx" indicates
professor xx in China is thoroughly informed of the world’s most advanced research in the field of xx.
And "this course will put xx in touch with the most advanced…" amounts to saying
this course will enable xx to become knowledgeable about the most advanced…
UPDATE: Distinguishing the meanings of different forms of 'in touch'
With regard to the request (in a comment below) by Kris for a source for the distinctions in meaning of "in touch" that I identified in the OP's various examples, the most useful reference I've been able to find is Christine Ammer, American Heritage Dictionary of Idioms (1994) who views "be in touch," "get in touch," and "keep [or stay] in touch" as being distinct but related idioms. Here is Ammer's entry for "in touch":
in touch, be Also, be in touch with. Be in communication or contact (with), as in Be sure to be in touch once you've arrived, or Our representative is really in touch with her constituents. A related idiom is get in touch, meaning "initiate contact," as in We tried to get in touch with you but you were out of town, and keep or stay in touch, meaning "remain in communication or contact," as in With Jim stationed in Korea, it was hard to keep in touch, or Do stay in touch with us. This idiom transfers physical touch to communication. [Late 1800s]
My sister complains that her friends' parents are very "out of touch" meaning they're clueless about the ways, mindsets and goings-on of teen culture and modern times in general.