None of the tests in that FAQ look to me like they could distinguish MWI from MWI+worldeater. The closest thing to an experimental test I’ve come up with is the following:
Flip a quantum coin. If heads, copy yourself once, advance both copies enough to observe the result, then kill one of the copies. If tails, do nothing.
In a many-worlds interpretation of QM, from the perspective of the experimenter, the coin will be heads with probability 2⁄3, since there are two observers in that case and only one if the coin was tails. In the single-world case, the coin will be heads with probability 1⁄2. So each time you repeat the experiment, you get 0.4 bits of evidence for or against MWI. Unfortunately, this evidence is also non-transferrable; someone else can’t use your observation as evidence the same way you can. And getting enough evidence for a firm conclusion involves a very high chance of subjective death (though it is guaranteed that exactly one copy will be left behind). And various quantum immortality hypotheses screw up the experiment, too.
So it is testable in principle, but the experiment involved more odious than one would imagine possible.
None of the tests in that FAQ look to me like they could distinguish MWI from MWI+worldeater. The closest thing to an experimental test I’ve come up with is the following:
Flip a quantum coin. If heads, copy yourself once, advance both copies enough to observe the result, then kill one of the copies. If tails, do nothing.
In a many-worlds interpretation of QM, from the perspective of the experimenter, the coin will be heads with probability 2⁄3, since there are two observers in that case and only one if the coin was tails. In the single-world case, the coin will be heads with probability 1⁄2. So each time you repeat the experiment, you get 0.4 bits of evidence for or against MWI. Unfortunately, this evidence is also non-transferrable; someone else can’t use your observation as evidence the same way you can. And getting enough evidence for a firm conclusion involves a very high chance of subjective death (though it is guaranteed that exactly one copy will be left behind). And various quantum immortality hypotheses screw up the experiment, too.
So it is testable in principle, but the experiment involved more odious than one would imagine possible.