Question

How would time travel work accordingto quantum physics?

Answer 1

It would mean travelling faster than light – and that's not possible. But there may be an out to be found in general relativity, Einstein's theory of gravity that unites space and time as “spacetime”, which curves in the presence of mass.

Answer 2

it's the physics that explains how everything works: the best description we have of the nature of the particles that make up matter and the forces with which they interact. Quantum physics underlies how atoms work, and so why chemistry and biology work as they do.