[ExI] Google’s Willow Quantum Chip: Proof of the Multiverse?

[Adrian Tymes]

On Mon, Oct 13, 2025 at 8:18 AM John Clark <johnkclark at gmail.com> wrote:
> I don't see how you can explain counterfactual quantum reasoning and such things as the Elitzur–Vaidman bomb tester without making use of many worlds. Hugh Everett would say that by having a bomb in a universe we are NOT in explode, we can tell if a bomb that is in the branch of the multiverse that we ARE in is a dud or is a live fully functional bomb.

Even MWI would not seem to explain it, as I read it, though I may be
misunderstanding.  Please correct if I've got this wrong, but I think
the claim is:

1) The photon either takes the upper path (away from the bomb) or the
lower path.  According to MWI, this fractures reality into two
separate worlds.

2) The photon - if it did take the lower path - interferes or does not
interfere (depending on whether there's a live bomb on the lower path)
with the photon if it took the upper path.

3) The result of this interference is then measured.

Do I have that right?

If so, the problem I see is that, according to MWI, the worlds diverge
as of step 1 - and worlds that have diverged do not have any
subsequent means of interaction.  That means that the possible
interference in step 2 could never happen.

If this interference is happening, then clearly something is getting
through the lower path even when the photon takes the upper path.