I'm not china-focused, but I applied this cycle with an explicit security studies interest/background and also approached the process only interested in top-10 programs. Harvard, Yale, and Columbia are all tbd, but I've had success with other programs and will most likely be at MIT in their security studies program in the fall.
Happy to chat about the process and different schools - applying with a security studies focus can be tough given its sometimes awkward footing in U.S. political science, so I'm happy to help out where I can. Feel free to shoot me a message.
Re. above At Harvard, you'd probably want to work with Alastair Iain johnston. He is absolutely China security focused. At Chicago, I'd take a look into whether Mearsheimer is advising (he may be, but definitely worth finding out).