Yeah, I just meant QM as meaning the semi-classical version. Making QM work with SR requires moving to QFT/"second quantization". You can presumably create pa

Yeah, I just meant QM as meaning the semi-classical version. Making QM work with SR requires moving to QFT/"second quantization". You can presumably create particle-like quanta with a creation operator that creates particles in position space vs momentum space. The particle then won't have a definite momentum in that case, so there's still an extent problem at least in configuration space. If there is an ultraviolet energy cut-off then you end up with problems as well. I think we perceive living in a position space more than we feel we live in a momentum space. We would prefer things to have a definite position more than we care about them having a definite momentum. The fact that they are conjugate observables is the troubling part.