“Point particle” is an approximation that doesn’t accurately predict reality. It only works at large actions. Classical is R^3, quantum is R^3 -> C. (Sort of;

“Point particle” is an approximation that doesn’t accurately predict reality. It only works at large actions. Classical is R^3, quantum is R^3 -> C. (Sort of; this glosses over a lot.) Objects don’t really have a concrete location; they have complex-valued distributions.