In considering a simple Young's double slit setup:
The classical idea that a particle must exist with defined position and momentum between the source and detection plate leads to philosophical angst, and Quantum Mechanics is most often interpreted (and in fact seems to make the most sense) if particles are not, in fact, "lumps of potato" between source and detection, but instead can only be said to truly exist at the point of detection.
In other words, the question of particle history, i.e. "What was particle 'b' DOING before I detected it?" is nonsensical in QM, and a ton of effort is spent getting us to stop thinking in this way.
My question is this:
Feynman's path integral approach and the improvement of Weak Measurements both seem to suggest that, while we may not be able to detect exactly which path a specific particle has taken to high degree of accuracy, there is in fact a particle that is taking a path in the first place. This seems contra to my understanding of QM, which explicitly works best if the very idea of particles taking defined paths of any kind is jettisoned as quickly as possible.
Further reinforcing the idea that particles are indeed, in some way, "lumps of potato" even when no attempt is made at weak measurement along their flight, is the matter of transit time:
Photons (or electrons, et al) generated at our experiment's particle source will not show up randomly at my detection plate placed 5 meters away; instead they will arrive in a predictable and timely manner such that I may start my watch when the photon is emitted and predict when it will hit my detector, as the photon will obediently arrive in the time dictated by c/5m. The very fact that the photon arrives in a repeatable and predictable period of time suggests that it exists during that interval period of time in some way, shape or form.
That the path integral approach works, that transit time is obeyed and predictable, and that weak measurements may be used to build up the "paths most traveled" all offer what seem to be at least circumstantial evidence that something does exist in the classical sense during the period of time between emission and detection, and I'm hoping the community can set me on the right path (pun intended) in reconciling these contradictions.