We finally did what we wanted to do for a while already: we produced a paper on the meaning of the wavefunction and wave equations in the context of an atomic lattice (think of a conductor or a semiconductor here). Unsurprisingly, we came to the following conclusions:
1. The concept of the matter-wave traveling through the vacuum, an atomic lattice or any medium can be equated to the concept of an electric or electromagnetic signal traveling through the same medium.
2. There is no need to model the matter-wave as a wave packet: a single wave – with a precise frequency and a precise wavelength – will do.
3. If we do want to model the matter-wave as a wave packet rather than a single wave with a precisely defined frequency and wavelength, then the uncertainty in such wave packet reflects our own limited knowledge about the momentum and/or the velocity of the particle that we think we are representing. The uncertainty is, therefore, not inherent to Nature, but to our limited knowledge about the initial conditions or, what amounts to the same, what happened to the particle(s) in the past.
4. The fact that such wave packets usually dissipate very rapidly, reflects that even our limited knowledge about initial conditions tends to become equally rapidly irrelevant. Indeed, as Feynman puts it, “the tiniest irregularities tend to get magnified very quickly” at the micro-scale.
In short, as Hendrik Antoon Lorentz noted a few months before his demise, there is, effectively, no reason whatsoever “to elevate indeterminism to a philosophical principle.” Quantum mechanics is just what it should be: common-sense physics.