Schrödinger's Rabbits The Many Worlds of Quantum (2004) / Chapter Skim
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16 Proving and Improving Many-Worlds
16 Proving and Improving Many-Worlds
Pages 228-250
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From page 228... ...
With the modest principle, "interference effects between worlds persist until a measurement of the self-interfering object is made in either world,' we were able to understand the workings not only of the Elitzur-Vaidman and Zeilinger designs, whidh use photons following different trajectories from the one in our "own" world, but more subtLy Me Paul-Pavicic monolith experiment that uses a photon that left at a different time than He one in our own world. I suspect that even considered just as a conceptua model, manyworlds has a great deal of further mileage waiting to be wrung out of it.
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From page 229... ...
But is there any hope of demonstrating that many-worlds is more than just an interpretation, or to put it another way, that those interpretations that do not accord other worlds equal status to our own are fa sitiable? David Deutsdh and Lev Vaidman have earth proposed hypoffietical experiments that would "prove" many-worlds by demonstrating interference with world lines that we would normally think of as having irreversibly decohered from our own.
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From page 230... ...
And even if that proof is obtained, it wit, arguably, show only that our world possesses certain extra degrees of freedom—that what Gell-Mann calls weak decoherence can occur—rather than the existence of strongly decohered world lines effectively independent of our own. There is always an understandable temptation for proponents of any particular quantum interpretation to see stronger evidence for it than a particular experiment provides.
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From page 231... ...
return to normal. The intermittent live shots start up again.
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From page 232... ...
As you continue to survive every time, despite the most rigorous Chewing of your equipment by independent experts, even the most hardened skeptics will begin to wonder.... In fact an analogous procedure was suggested in a detective story written decades ago.
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From page 233... ...
If Me green light shines, he must open the safe and tell you the number. But if the red light shines, he can keep Me safe looked—and just after midday, you will ted him Me number, transmitted as a signal from the offer world where the green lamp shone.
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From page 234... ...
The overwhelmingly majority view is that the worlds would completely decohere at the moment He green and red lamps lit, induding divergent versions of the Sdhrodinger's-cat ion. To the best of my knowledge, He experiment has not even been tried in the decade since it was proposed.
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From page 235... ...
Communication between parallel worlds is fun to explore as a science-fiction theme. In my opinion the consequences that would tallow have not yet been worked out as ffioroughly in contemporary science fiction as other hypoffieticaL scenarios—time travel, matter transmitters, and so forth—were explored
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From page 236... ...
new measures of world lines, diverging from those that produced your originaL memories. A more promising line of approadh, however, is to strengthen We phiLosophicaL case for many-worlds.
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From page 237... ...
This conforms to our intuitive expectation—aLffiough perhaps it generates our intuitive expectation—that a universe that can be defined by a smaLL amount of information, however large Me volume of space and time it might eventuaLLy expand into, is much more likely than a universe embodying a vast set of ruLes or a quirky set of initiaL conditions that wouLd require a great deaL of information to describe it. Max Tegmark has identified a troubling problem with this cosy "universe from a tiny package of information" view.
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From page 238... ...
To write down a specific sequence of the result of tossing a classical or quantum coin a million times requires a million binary digits. But to teL you that He result is 2' °°° °°° equal measures of universes in whidh each of these sequences occurs takes just a single sentence.
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From page 239... ...
" the unsympathetic answer is, "That's just He way it looks to you. Actually, every typographically describable sequence of events happens to some equally real Hamlet somewhere in the library!
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From page 240... ...
An earlier iLLustration we used featured a man-made object of this kind, a computer made of opticaL fibers through whidh different wavelengths of light are transmitted by deliberately contrived arrangements of fiL
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From page 241... ...
However, Me direction and magnitude of Me tiny gravitational force that Alpha Proximi exerts remains roughly constant over thousands of years, adding up to a significant effect.
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From page 242... ...
In biology, We laws of evolution naturaLLy cause species to split into subspecies that can no longer interbreed, and diverge thereafter. In chemistry, there are reactions so specific that two or more different chemical processes can be taking place in We same test tube whi e having virtuaLLy no effect on one another.
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From page 243... ...
But an essentia feature of all these models is that rather than every region of space containing an infinite amount of information—as would be required, for example. to define the exact value of a classical field at every point throughout the region—a given volume of space, say I cubic centimeter, requires only a finite number of binary digits to describe its state precisely.
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From page 244... ...
244 / Schrodinger's Rabbits .
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From page 245... ...
Are we ta king one-dime 2siona strings or two-dimensiona membranes, and embedded in a space of how many dimensions? This picture is a most certainly an oversimplification, are lost in the mists of time; We French meter represents a saightLy inaccurate guess at I tom, -millionffi of Earths equatorial circumference, intended to make navigational calculations easier)
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From page 246... ...
The Nobel Prize winner van 't Hooft has given a memorable way to visualize this. If you imagine He surface enclosing a region of space as a flexible computer screen, each of whose pixels is exactLy 2 x 2 Planck units and can be either black or white, then He surface of He screen encodes all He information that region of space contains.
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From page 247... ...
If a multiverse-computer has a storage capacity of I bit per cubic Planck unit, and supports a multiplicity of the reasonably stable entities we have dubbed loca worlds, obviously not aLL of the worlds can make independent use of We same storage. A problem wiLL arise raffler like that of sharing a f nite amount of radio waveband between different users; the more transmitters, We more unavoidable cross-talk there is as each extra user contributes to We generaL background of noise.
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From page 248... ...
For example. consider a simple quantum entity, a photon that has passed through a polarizing filter set at 38.123456789 degrees to Me horizontal.
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From page 249... ...
It must foLow a simple deterministic update rule, with Me state of each Plandk volume of space (probably represented by a single pixel on the screen) changing each time step in a local way determined only by its own state and that of its immediate neighbors.
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From page 250... ...
lust as the opticaL-fiber computer we met earlier couLd perform thousands of caLcuLations in paraLLel using no more hardware than required for a single conventionaL computer, so a slight difference in We Laws of physics couLd make We difference between a universe that can run only one world ine and a mu tiverse that can run a colossaL number. If a muLtiverse represents a vastly more efficient use of resources, in terms of We number of inteLLigent species or individuaL beings it can contain per unit of information processed, then is it not statisticaLLy aLtnost inevitable that we find ourselves in such a placed But now I am treading very dose to the line that separates physics from metaphysics, and it is definitely time to bring this book to a close.
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