If you argue that branch communication is not real, there should be a reason: either MWI is false or in this exact setup there is some technical or theoretical flaw.
MWI in the usual sense follows quantum mechanics, which predicts that branch communication is not real. An observation that branch communication is not real agrees with MWI, it doesn’t suggest that “MWI is false”.
As I think you are pro-MWI and there is not much technical details, there should be some theoretical problem. What it could be?
Like with any other metaphorical perpetuum mobile, the exact technical issue is not very interesting. To the first and second approximations, the exact issue shouldn’t matter, a form of argument that demands tracking down the issue is already on the wrong track.
If we take relative states interpretation of Everett (of which MWI is simplification), there is no exact prohibition, but the interference between branches becomes infinitely minuscule very quickly. The only exception is the state of entanglement or any quantum state where a particle has quantum state and didn’t yet collapsed to any of eigenvalues.
So the lack of interaction between branches doesn’t apply to this experiment because we have trapped ion which still remains in its quantum state.
The problem of the experiment was explained to me in the comment below: If you excite the ion in one branch, it becomes entagled with that branch and stops being non-entagled with anything. It is easy to see from energy conversation: if I have excited the ion I spent some energy, but if I see the ion excited in another brach, this energy would come from nowhere, which is prohibited by conversation law. I think that instead of exciting ion, the senders have just to measure it. And the receiver will have to measure if ion remains in quantum state or is in one of eigenstates.
You are tracking down and patching the issue. Imagine a perpetuum mobile developer who had a specific issue pointed out to them, and who frantically redesigns the contraption around the place in its mechanism where the issue was identified.
(The perpetuum mobile is metaphorical, an analogy about methodology in reasoning around local vs. global claims, one that also carries appropriate connotations. I’m not saying that literally conservation of energy is being broken here.)
MWI in the usual sense follows quantum mechanics, which predicts that branch communication is not real. An observation that branch communication is not real agrees with MWI, it doesn’t suggest that “MWI is false”.
Like with any other metaphorical perpetuum mobile, the exact technical issue is not very interesting. To the first and second approximations, the exact issue shouldn’t matter, a form of argument that demands tracking down the issue is already on the wrong track.
If we take relative states interpretation of Everett (of which MWI is simplification), there is no exact prohibition, but the interference between branches becomes infinitely minuscule very quickly. The only exception is the state of entanglement or any quantum state where a particle has quantum state and didn’t yet collapsed to any of eigenvalues.
So the lack of interaction between branches doesn’t apply to this experiment because we have trapped ion which still remains in its quantum state.
The problem of the experiment was explained to me in the comment below: If you excite the ion in one branch, it becomes entagled with that branch and stops being non-entagled with anything. It is easy to see from energy conversation: if I have excited the ion I spent some energy, but if I see the ion excited in another brach, this energy would come from nowhere, which is prohibited by conversation law. I think that instead of exciting ion, the senders have just to measure it. And the receiver will have to measure if ion remains in quantum state or is in one of eigenstates.
You are tracking down and patching the issue. Imagine a perpetuum mobile developer who had a specific issue pointed out to them, and who frantically redesigns the contraption around the place in its mechanism where the issue was identified.
(The perpetuum mobile is metaphorical, an analogy about methodology in reasoning around local vs. global claims, one that also carries appropriate connotations. I’m not saying that literally conservation of energy is being broken here.)
I think it ok to try to patch if costs to check are small and gains if it works are enormous. Any perpetuum mobile developer would say this.
I think that prohibiting is not that strict in the case inter-branch communication when in the case of energy conversation, so adding tricks can work.