Seasons

Well, at this point, the wave theory looks pretty good! However, there is one thing that is a little mysterious. When the soprano sings very softly, the glasses break one by one. But, curiously enough, occasionally it happens that a glass will break in a region where the amplitdue of the wave is relatively small (i.e., the sound of her voice is not loud), while the glasses in a region where the amplitude is high remain unbroken (for the time being). Observation over a long period of time shows that the probability of a glass breaking is higher where the amplitude of her voice is greater; in the long run, then, there will be more damage in the regions of greater amplitude, but from time to time, something improbable can happen, namely a glass breaking in a quiet area.
So they conclude that there is a wave, but the actual damage done is not done inevitably by the wave (else all the glasses in areas where the wave is strong would break if even one glass broke in the quieter areas), but rather that the amplitude of the wave in the neighborhood of a glass gives the probability that the glass will break.
When the soprano sings louder, so many glasses break in a short time that the amount of damage in a region clearly reflects the probability of breakage in that region, so that diffraction and interference patterns become immediately visible. But the same thing happens over the long run; if the soprano sings softly, but sings over a long period of time, these patterns eventually emerge, 'by the law of averages.'

Now, all by itself, the fact that a glass will break while other glasses in areas of equal or greater intensity do not would seem to support the spit-bullet theory: the effect is local because a spit bullet is small. "If it were a wave," argue the spit-bullet proponents, "it would spread out, and wherever the amplitude was sufficiently high, all the glasses would break at once." However, the proponents of the probability wave theory have an answer to this (see my previous post), and besides, the spit bullet theory can't explain diffraction, interference, and tunneling.
So we conclude with a theory has is in some ways a wave theory and in some ways a particle theory. It is a wave theory in that causation propagates as a wave, but it is particle-like in that its effects are highly local.
Also, the source of the wave is local, or, to use that delicious word, punctiliar (like or occurring at a point).

So I am not a wave-only theorist; I might however be called a propagation-by-wave-only theorist. I see no need for a particle that traces a unique, continuous path from source to target; but then, neither do you, Psimagus, since you say that the particle in the two-slit experiment goes through two slits at once. If you want to say, with David Bohm, that punctiliar particles ride on the wave, tending to the high points, I don't know of any contradiction you will get into; but since the wave alone is sufficient to explain everything, except at source and target, Occam's Razor would tend to shave them off.

Wait! Irinia says there is a particle like energy which travels in waves and has characteristics of both, and Psimagus says there is a wavicle, which is a partile-wave thing that shows characteristics of both. What exactly is the difference?

As for quantum computers, they would have to be largely based on wave behaviour, since, as I understand it, they mustn't decohere until the computation is finished. The computation is done with waves, the I/O is punctiliar.