The question is fine, but I think still a bit difficult to answer in a non-subjective way.
A cursory exploration on google will provide you with examples of papers proposing computing paradigms based on things such as effects of general relativity (gravitational waves) or string theory, and probably other similar examples.
I am not qualified enough in those subjects to assess the accuracy or seriousness of such proposals. However, what I think it's fair to say is that there is no alternative model of computation that is widely believed to be "better" than quantum computation (or better stated, no physical phenomenon that is widely believed to not being efficiently simulatable with a quantum computer). This is sometimes referred to as the physical Church-Turing thesis.
Does this mean that there is no such thing? No, it means that we have no clear and non-controversial evidence pointing in that direction (I use these qualifiers because I guess it could be argued that there are phenomena which are not well-described by our current physical theories -- cue merging of QM and general relativity etc. -- so there could be room for something more happening there, but we simply don't know for certain yet).