I think that sometime between now and when you apply to master’s degree programs it is very, very likely that you will change what subject you intend to focus on for your master’s degree.
However, some combination of physics, mathematics, and computer science can be used in quite a few ways. Just as one example, you could start on this path thinking “quantum computing”, and six or seven years from now (after a bachelor’s degree and some time working on a job) change to “artificial intelligence” or “machine learning” or “operations research” or “particle physics” or “acoustics” (assuming that you take the right math and physics, which is likely for someone aiming for quantum computing), or any one of a very wide range of other fields.
I do not think that you need to be too concerned right now about the specific manner in which you are going to apply interest in some combination of physics, mathematics, and computer science.