In the thread https://physics.stackexchange.com/questions/456464/localization-of-electron-matter-field-excitation-in-simple-electron-qft-model a vital question about QFT is asked namely ´what keeps the electron matter field excitation localized instead of dispersing out through the extended field´. It is stated in the answer there that the coherent state describes a classical particle from point of view of QFT. This somehow answers the question but it is unclear 1. why does Quantum mechanics  not use coherent state and subsequently avoid all troubles with wave-particle duality as Schoedinger attempted in the beginning? 2. If one measures the impulse of the the source the coherent packet should vanish instantaneously and the experimentally observed localization of the electron could not be explained with it anymore. 3. how will coherent state manage the double slit experiment? if the packet is localized where would interference come from?