The way some of such experiments are done is by creating entangled photons and observing (or not observing) the second photon. No interaction with the first photon, except mysterious instantaneous wave function collapse. Also known as Magic.

So, it's fine that you don't understand the experiment, it's really confusing and not intuitive. It's not that the photons change their behavior when measured. It's that they pass through two different slits as a probability field, and the field collapses as soon as it is measured in any way. It's not just that the behavior changes, the nature of the photon changes. It doesn't exist as a single point in spacetime until it is measured.

Thank you. I had someone sit for about 30 minutes trying to convince me our eyes, without any level of interaction, changed the behavior of photons and quantum particles simply by the fact we were gazing at them. I could not understand how but kept being reassured it was the case.

So you’re telling me that the double slit experiment has reached a sufficient saturation point in modern culture so as to have a conspiracy around it?

Wheeler's delayed-choice experiments demonstrate that extracting "which path" information after a particle passes through the slits can seem to retroactively alter its previous behavior at the slits.

from the Wikipedia article on the double-slit experiment

If you read through Wheeler's delayed choice experiments, all the variations he went through to try to pin this down, well... it's hard to avoid the conclusion that the waveform doesn't collapse until the moment that someone looks at the data. In fact, it's hard to avoid the conclusion that the universe is laughing at us every time we try to get a specific answer. This statement from the conclusion is absolutely bonkers if you think about it:

The fact that it is possible to decide whether a wave or particle feature manifests itself long after—and even space-like separated from—the measurement teaches us that we should not have any naive realistic picture for interpreting quantum phenomena.

The method of observation determines whether the photon behaved as a wave or a particle, after the measurement is done.

Our results demonstrate that the viewpoint that the system photon behaves either definitely as a wave or definitely as a particle would require faster-than-light communication. Because this would be in strong tension with the special theory of relativity, we believe that such a viewpoint should be given up entirely.

The photon behavior as recorded changes depending on how you examine the record, even "long after" the record is made and the interpretation should be fixed. It quite literally depends on how you look at it.

I mean, magic is just weird shit that isn't fully understood yet.

That being said, you might as well look at it as branches.

Each state is a possibility, thus both exist.

The "magic" isn't that the probabilities of either state being in effect suddenly collapsed and became reality. The magic is that by observing the result, we collapse our own probability and are suddenly aware of the branch that we exist in. But we also exist in that other branch, suddenly aware that we exist in it. But "both" of us are incapable of viewing that other branch.

Which is all mumbo-jumbo, but I'm a fiction writer, so I don't have to be rigorous :)

There's actually no way to prove or disprove consciousness collapse theories, as even if an unmonitored detector causes collapse, you only know about it when a consciousness is reviewing the data. So at best it can be said that direct consciousness collapse theories aren't true, but AFAIK the ones still around are all indirect (i.e. collapse occurs at the point you are reviewing the data).

We could similarly talk about the "woo woo" of multiverse theories and how there's no proof for Everett's interpretation (despite being one of the few popular theories not to need an invalidation of an assumption in the Frauchiger-Renner paradox).

But no proof doesn't equal "not true."

All QM interpretations are up in the air, and an appeal to Copenhagen interpretation is probably one of the most nonsensical given a specific interpretation doesn't even exist for that one and it's effectively just become euphemistic for "shut up and calculate."

Which is now being taken advantage of to improve experimental results.

Like the singularity of a black hole

The double slit expiriment demonstrates the duality of the nature of a photon: that it's both a wave and a particle.

When a photon is "observed" (or detected) it has the properties of a particle. However when it's travelling it acts like a wave and can demonstrate interference patterns with other photons.

So when you pass photos through two tiny slits, instead of them just passing right through like a particle, they interfere with each other and when the wave pattern collapses when it is observed on the wall, you see the interference.

That being said, I don't think this cartoon makes sense. I get what they are driving at, as they are saying it acts differently when not observed, but this is not what happens. Also this isn't a ln experiment that deals with observation forcing an outcome, but as I noted it's about the duality. Additionally, the wave pattern on the top is what you would you observe when looking at, so I'm not sure why that is what it would be like if you were looking away.

But maybe I'm missing something.

The double slit experiment demonstrates the wave-particle duality of light.

You shoot photons at a barrier that has two slits in it. The pattern on the backstop appears as in the top right panel: an interference pattern, because light is behaving as a wave.

Next, you set up a detector at the slits, so that you can determine which slit each photon passed through, one photon at a time. Now the pattern on the backstop appears as the lower right panel, not an interference pattern, because each photon is acting as a particle.

Not looking: wave. Looking: particle.

TLDR the goddamn universe makes no fucking sense if you really look at it.

Young's double slit experiment.

When which slit a photon goes through is unobserved, it behaves like a wave and self interferes so many photons create an interference pattern with stripes where self-interactions prevented any photons from appearing.

When the photon is interacted with in a way which leaves permanent information about which slit it went through, it behaves like a particle and the pattern from many photons looks 'ballistic' like you were shooting tiny balls through each slit.

So in the meme when he's not looking at the slits, there's stripes, and when he's looking it's a ballistic pattern.