Can a Chinese citizen who is visiting the United States bring a personal
computer out of the US into China?  If yes, are there any tariffs or duties that
will need to be paid?

Hi,

I cannot quote any official regulations here, but offer my personal
experiences and those of many friends who bought their computer in the
US and brought it back. For personal use there is absolutely no
problem: personal computers are so much a part of daily tools, nobody
will ask any questions.
There are ways to get into problems and I got good advice on that. Do
remove any boxes and make clear your computer is really meant for
personal use. Second, do take only one computer. When you bring in
five, you might get into trouble.
No worries,