Where and why do you think you’d need to use C/C++ or Rust along with Julia?
I ask, because when I first learned Julia (almost 6 years ago) I thought I’d need to write some of the code in C for performance. After I was shown a few simple “tricks” (like using @inbounds when I knew it was safe to do so, checking for type stability, being careful about allocations), I was able to match the performance of my C code (and I’d had 3 decades of experience C/C++/Assembly, specifically in the area of optimizing code).
So far, although I’d like to learn Rust in case I ever do need to make a nice shared library (to be called from Julia, of course!), I’ve not once actually needed to, Julia has given me all the performance I needed, and was easier to write and maintain.
On a different note: have you heard of Quantum Chess? ;-). I hadn’t played chess in almost 50 years, until we played Quantum Chess over lunch at Zapata Computing, it was a lot of fun!