Every quantum event splits the multiverse, so my measure should decline by 20 orders of magnitude every second.
There isn’t the slightest evidence that irrevocable splitting, splitting into decoherent branches occurs on that scale, and plenty of evidence—eg. the existence of quantum computing—that it doesnt.
“David Deutsch, one of the founders of quantum computing in
the 1980s, certainly thinks that it would. Though to be fair, Deutsch
thinks the impact would “merely” be psychological – since for him,
quantum mechanics has already proved the existence of parallel uni-
verses! Deutsch is fond of asking questions like the following: if Shor’s
algorithm succeeds in factoring a 3000-digit integer, then where was
the number factored? Where did the computational resources needed
to factor the number come from, if not from some sort of “multiverse”
exponentially bigger than the universe we see? To my mind, Deutsch
seems to be tacitly assuming here that factoring is not in BPP – but
no matter; for purposes of argument, we can certainly grant him that
assumption.
It should surprise no one that Deutsch’s views about this are
far from universally accepted. Many who agree about the possibil-
ity of building quantum computers, and the formalism needed to
describe them, nevertheless disagree that the formalism is best inter-
preted in terms of “parallel universes.” To Deutsch, these people are
simply intellectual wusses – like the churchmen who agreed that the
Copernican system was practically useful, so long as one remembers
that obviously the Earth doesn’t really go around the sun.
So, how do the intellectual wusses respond to the charges?
For one thing, they point out that viewing a quantum computer in
terms of “parallel universes” raises serious difficulties of its own.
In particular, there’s what those condemned to worry about such
things call the “preferred basis problem.” The problem is basically
this: how do we define a “split” between one parallel universe and
another? There are infinitely many ways you could imagine slic-
ing up a quantum state, and it’s not clear why one is better than
another!
One can push the argument further. The key thing that quan-
tum computers rely on for speedups – indeed, the thing that makes
quantum mechanics different from classical probability theory in the
first place – is interference between positive and negative amplitudes.
But to whatever extent different “branches” of the multiverse can
usefully interfere for quantum computing, to that extent they don’t
seem like separate branches at all! I mean, the whole point of inter-
ference is to mix branches together so that they lose their individual
identities. If they retain their identities, then for exactly that reason
we don’t see interference.
Of course, a many-worlder could respond that, in order to lose
their separate identities by interfering with each other, the branches
had to be there in the first place! And the argument could go on
(indeed, has gone on) for quite a while.
Rather than take sides in this fraught, fascinating, but perhaps
ultimately meaningless debate...”..Scott Aaronson , QCSD, p148
There isn’t the slightest evidence that irrevocable splitting, splitting into decoherent branches occurs on that scale, and plenty of evidence—eg. the existence of quantum computing—that it doesnt.
“David Deutsch, one of the founders of quantum computing in the 1980s, certainly thinks that it would. Though to be fair, Deutsch thinks the impact would “merely” be psychological – since for him, quantum mechanics has already proved the existence of parallel uni- verses! Deutsch is fond of asking questions like the following: if Shor’s algorithm succeeds in factoring a 3000-digit integer, then where was the number factored? Where did the computational resources needed to factor the number come from, if not from some sort of “multiverse” exponentially bigger than the universe we see? To my mind, Deutsch seems to be tacitly assuming here that factoring is not in BPP – but no matter; for purposes of argument, we can certainly grant him that assumption. It should surprise no one that Deutsch’s views about this are far from universally accepted. Many who agree about the possibil- ity of building quantum computers, and the formalism needed to describe them, nevertheless disagree that the formalism is best inter- preted in terms of “parallel universes.” To Deutsch, these people are simply intellectual wusses – like the churchmen who agreed that the Copernican system was practically useful, so long as one remembers that obviously the Earth doesn’t really go around the sun. So, how do the intellectual wusses respond to the charges? For one thing, they point out that viewing a quantum computer in terms of “parallel universes” raises serious difficulties of its own. In particular, there’s what those condemned to worry about such things call the “preferred basis problem.” The problem is basically this: how do we define a “split” between one parallel universe and another? There are infinitely many ways you could imagine slic- ing up a quantum state, and it’s not clear why one is better than another! One can push the argument further. The key thing that quan- tum computers rely on for speedups – indeed, the thing that makes quantum mechanics different from classical probability theory in the first place – is interference between positive and negative amplitudes. But to whatever extent different “branches” of the multiverse can usefully interfere for quantum computing, to that extent they don’t seem like separate branches at all! I mean, the whole point of inter- ference is to mix branches together so that they lose their individual identities. If they retain their identities, then for exactly that reason we don’t see interference. Of course, a many-worlder could respond that, in order to lose their separate identities by interfering with each other, the branches had to be there in the first place! And the argument could go on (indeed, has gone on) for quite a while. Rather than take sides in this fraught, fascinating, but perhaps ultimately meaningless debate...”..Scott Aaronson , QCSD, p148
Also see
https://www.lesswrong.com/posts/wvGqjZEZoYnsS5xfn/any-evidence-or-reason-to-expect-a-multiverse-everett?commentId=o6RzrFRCiE5kr3xD4
But if I use quantum coin to make a life choice, there will be splitting, right?