Can you elaborate on the portal? What does it do, is it between two locations or is it just a hole, or is it just a black circle?
Physics
The scientific method doesn't rule out any phenomena, it simply provides a method of investigating phenomena.
I should have put more emphasis on the other part: The possibility, however unlikely, that a wave function "cascade" would create (what at least appears to be) a black portal.
a wave function "cascade"
I'm not sure what you're referring to. It sounds like you've heard some physics words, misunderstood them, and are regurgitating them based on that misunderstanding.
I'm asking questions based on "physics words" I've heard, yeah.
I just used cascade to describe many waves collapsing to create a whole.
I'm asking if the wave functions in the particles around us could collapse in such a way that they could absorb light, or even change the composition of atoms?
Since you're seeking for answers within physics buzzwords, you're missing a lot of nuance which is causing you to come up with nonsensical theories. For one, the wavefunction doesn't exist 'in' the particle, it is the particle. A wavefunction collapsing is what causes a particle to show up in a specific location (going by the most prominent interpretation of the wavefunction); as long as the wavefunction is non-zero at more than one location, the particle exists in all those locations.
Equipped with this knowledge, phrases like "a wavefunction collapsing in such a way that it absorbs light" or "change the composition of atoms" make no sense, so I'd suggest you to rethink your assumptions, and, if possible, not look at quantum mechanics as a magic black box that can explain everything a mind can conjure up.
I'm asking if the wave functions in the particles around us could collapse in such a way that they could absorb light, or even change the composition of atoms?
Your question doesn't make sense.
The scientific method can't rule out the existance of supernatural stuff like gods or magic. And you can totally explain a black portal (or literally anything you want) with magic or the actions of a god.
Can they be explained by quantum states being in an incredibly unlikely but not impossible state?
Is it really an explanation if it requires something so incredibly unlikely?
I think you will have a much better chance for finding an explanation by looking into optical illusions or hallucinations.