The quantum source of space-time(nature.com) |
The quantum source of space-time(nature.com) |
https://www.youtube.com/watch?v=PSYXt3Xu3xI
I'm not a physicist, but he seems to be invoking similar ideas to Raamsdonk: that spacetime and gravity are emergent properties that boil down to entanglement somehow. But the loop quantum gravity people have been saying something like that for ages. And Stephen Wolfram and Konrad Zuse etc. And we have people like Lubos Motl on the other hand to ridicule all of the above.
Anyone able to give a big picture overview of what's been happening the last few years in this somewhat rarefied world? Who are we, the intelligent lay public, to trust?
The most interesting (to me, at any rate) bit of this article are susskind's observations on computational complexity. As a precocious undergrad I put forward the idea that gravity and time dilation were the same thing, and both stemmed from the universe needing a constant amount of "time" to compute the interrelations between the particles in a volume of space - and if there were more particles more time would be needed as the graph of particle interactions would grow non-linearly - and therefore time "slows down" in a matter (information) dense area of spacetime.
What really got me gunned down was then going on to argue that this suggested a simulated universe, running in a substrate.
Either way, interesting to see someone else who actually has some clout having similar ideas.
To me, the language here is important. Both simulation and computation imply (to me) a tool and a user of the tool. Even a broader interpretation of computation as, umm, the efficient transfer of precise information through spacetime in certain shapes (which is easily providable by our understanding of physics today) requires an observer to extract the computation from the otherwise non-semantic system.
It definitely makes sense to think of the universe as a projection of a higher dimension, or a holograph, or however you want to look at it, but that's a far cry from implying a simulation.
EDIT: hologram -> holograph
I wonder if the trick about this is not really to find a true explanation but the right perspective and more and more simulation seems to be a very valuable perspective to put on this.
Disclaimer — I am not a physicist so apologies if my question is stupid.
Anyway, the part that I know, and which is well established, is that there seems to be a correspondence between a d+1 dimensional quantum gravity theories, and d dimensional quantum field theories (e.g the standard model). A while ago this was still purely conjecture, but Maldacena showed that this correspondence was true (under certain conditions) for an AdS space with a conformal field theory on its boundary. As far as I know this is now pretty well established, most of the discussion seems to be on how much it can be generalized.
From my (limited) understanding it seems that (in AdS/CFT) entangled particles tend to correspond to strings traversing from one part of the boundary, through the bulk, to another part of the boundary, the space the string travels through then forms a tube like object. This gives a link between entanglement and geometry, since these tubes exist if and only if the two points on the boundary are connected.
I think it isn't disputed that this happens for AdS/CFT, but whether something similar is true for our universe is debatable. If however it turns out that the holographic principle does hold in general then that would imply that our universe somehow corresponds to a 2+1 dimensional field theory, where entanglement of this field theory is responsible for the fact that our space-time is connected.
[1] https://scholar.google.no/scholar?cluster=132568844183140142...
In other words, there's no such thing as "spooky action at a distance", because with particles joined by a wormhole there is no distance between them?
There are two unifications that need to happen. One is the unification of the strong force with electro-weak force(the unified version of electromagnatic force and weak force). The other is gravity with the unification of the three forces.
As far as I understand, this work is concentrating on the second unification, and not the same. Though it might open the door for the first one too. Someone closer to this area should comment.
Can anyone explain to me why it can't simply be a force? If you accept that gravity is caused by energy and not mass (which is obviously the case), then I see no reason a photon can not experience a force.
So what is the reason to insist it's geometry?
And related to that, I still have never seen an explanation of how geometry is supposed to cause something to start moving without a force. Explaining how it deflects something, I get. How does it start moving in the first place?
The only explanation I've gotten is that things are always moving - through time, and the geometry just transfers some of that motion into physical motion. But that explanation is very very very lacking since all things do not move through time at the same rate (because of the various types of time dilation that are possible), yet the gravitational force is identical.
No. No! No!!! This meme has really got to die. A measurement of one entangled particle does NOTHING to the other particle. Its state is exactly the same as it was before. In fact, the whole concept of "before" and "after" a remote measurement doesn't even make sense because it depends on your frame of reference!
Entanglement lets the measurement of one particle
instantaneously determine the state of a partner
particle, no matter how far away it may be — even
on the other side of the Milky Way.
If I have a bag of coins, and I take out all of the copper coins, it's not very mysterious that the bag now contains only silver coins, no matter whether I hide it under my bed, or in the freezer, or hang it out the window.
Yes, all the copper coins are now absent from the bag, forcing it into an all silver state, and I can know this, without even looking at the bag. I take the bag, and I drive it across town. I hide it under a rock. I go home. I think about the bag under the rock. I can instantaneously know that the bag contains only silver coins, even though it's across town, hidden under a rock. Instantaneous. I determine the state of the bag. With my mind. Just by thinking. Even across town. So amazing.
Why do journalists and scientists so deeply covet the seeming appearance of the arcane?
Rotation of Earth around Sun is just a process, there is no time in it apart from the mind of an external observer. Similarly with any so called "atomic clocks" or any other physical process, including so called expansion of the Universe.
Time, of course, could be derived as a concept from an observable change (a process) by mind, but this does not imply its physical existence, like it is with what we call physical forces.
Space is more subtle, but it is also require an observer and at least two particles related via this or that set of forces.
Two random Photons share nothing, and without an observer there is neither space nor time among them.
Mathematics does not imply existence of described abstraction.
Western philosophy, so far, succeed in separating these concepts as being a priory which is perfectly reasonable, considering that any sensory input which is subsequently used to train and condition our mind is coming serialized by out sense organ, so, for a mind, which is a result of conditioning by the senses, the notion of succession is a priory. Conditioning by shared physical environment gives us cycles, so the notion of a cycle is also a priory. Succession days into nights in the environment and ageing of other people's bodies gives us notion of a continuous change. But change is not time.
Eastern philosophy (and modern cognitive neuroscience) would suggest that this a priory is related to our minds, not to photons or forces. So?
Remember the correspondence principle will still be in play; future quantum theories will still have to limit out to what we know today, because the QM of today is arguably the most rigorously tested theory in humanity's history, by number of significant digits. FTL communication still will have all of the problems conventional relativity says it will, for all the same reasons.
Entanglement has suggested for a long time that there may (in clumsy English words) be some sort of "real reality" that isn't necessarily constrained by what we think of as space and time. In fact even relativity looked at in a certain manner has suggested this; you can travel from any point in the universe to any other, barring black holes, along null spacetime intervals. Null spacetime intervals have no distinction between the points in them, because they all come out the same 0 in the metric measurement. I wouldn't expect that any of this new math is going to change anything; it may explain where the constraints of space and time come from, but explaining the constraints doesn't mean that the explanation will come with a way to get around them!
In fact my personal observation is that the fundamental limits of space and time have been getting stronger as we learn more about physics, not weaker; a mathematically rigorous derivation of the fundamental speed-of-light limit from a "more fundamental" level of reality locks the door even tighter, it doesn't open it.
The crucial concept is Newton's first law (objects continue on their trajectory if a force is not applied). The straight lines in the 4D spacetime (geodesics) - the lines that an object would follow if no force is applied - correspond to the paths that look as if a gravitational force is applied.
- The surface of the earth is a 2 dimensional positive curved space. To see this, draw a triangle with corners on the north pole, on the equator near Somalia and on the equator in Equador. The resulting triangle has a sum of all corners > 180 degrees.
- In a negative curved space, the sum would be less than 180 degrees. In a flat space, it is equal to 180 degrees.
- Another way to see the curvature of the surface of the earth is to observe that it's impossible to draw 2 parallel lines that do not intersect.
- The 2D torus (e.q. the surface of a donut) is flat. Test it with triangles.
- The towers of the Verrazano–Narrows Bridge are wider at their top than at their base. This has nothing to do with the earth have a positive curvature. Test it with a torus.
- 3D space is nearly always flat in the universe, especially at the surface of our planet.
- 4D space-time is not remotely flat. If I throw up a ball, it will come down. This is due the mass of the earth curving its surrounding 4D space-time. The straight line for a ball in the curved space-time looks like the ball changes directions and comes down in our flat 3D space.
- If you try to find the triangle of a sphere with the biggest sum of corners, you'll discover that the outside and inside of a triangle are interchangeable. We've entered the field of topology now and this has nothing to do with its curvature.
This is the crucial point that many discussions overlook. The concept of "curvature of space" is obvious nonsense because curvature is measured with respect to space. For space itself to curve implies the existence of meta-space (and as many nested metaspaces as you like). But "spacetime" does not work like "space", and there actually is no metaspace. Talking about "space" curving or expanding is unnecessarily confusing.
It could be a force - if someone finds a theory that describes all the observational data. They haven't.
The reason to insist geometry is that general relativity manages to predict extremely accurately the result of all gravitational experiments/observations as of 2015. In science, prediction comes before explanation, meaning if you have to accept whatever explanation the best predictive theory offers and not vice versa.
Well, its has been explained - you just haven't gone through the right books. There are two answers, which I will simplify. One, the Big Bang threw everything all over the place and now masses are moving so as to reach the state of minimum energy. Two, there are 3 other forces in the universe which can cause masses to move. For example you can use electromagnetic forces during the combustion of rocket fuel to send a satellite in space. The satellite then moves in orbit because of the geometry of spacetime. Same when stars explode - this involves all three forces.
I'm going to be a little picky about your choice of language here.
It seems to me that, at least that your are predicting randomly, you can't possible make predictions with a good model, that is, a good explanation.
And I didn't say the state of the particle was already determined. It wasn't. Yes, of course superpositions are real. Yes, of course the Bell inequalities are violated. Yes, this eliminates all local hidden variables theories. Yes, it seems like this necessarily leads to the conclusion that there is spooky action at a distance. But that's wrong. To see why, read the paper or watch the video.
The correct story is that measurement and entanglement are the same physical phenomenon. The creation of an EPR pair is the first step in any measurement process. The correlations in EPR measurements derive from exactly the same physical process as the correlations in "ordinary" measurements (I put "ordinary" in scare quotes because, as I said, even "ordinary" measurements start with the creation of an EPR pair). When you "measure" the two halves of an EPR pair what you are really doing is performing two measurements on whatever system produced the EPR pair to begin with. When you look at it that way it is not at all surprising that the measurements should be correlated.
For more details see:
Yeah, it does, amongst other things. Unfortunately in that context two of its meanings (to discover & to decide) could have been appicable.
So the real problem isn't that "when one is up, then the other will magically be up too." That could be accomplished with local hidden variables (e.g. shared seeds on a PRNG, or your examples).
The real problem is that when you measure A in the "up" direction, and then B in the "10 degrees east of up" direction, then B seems to know that you measured A in the "up" direction.
That is to say: B's probability distribution as a function of the direction its being measured is correlated to the direction that A is measured. There's no way to construct an "A-independent" probability distribution of B's results for arbitrary directions. The probabilities won't sum to 1 and still match experimental results.
It's unfortunate that "A up" therefore "B up" is a degenerate case of this reality where classicality actually works, because it leads to confusion.
(Also the reason you can't use this magic to communicate FTL is that you can only ask one yes/no question of each particle, and because B's probability distribution is distorted in a symmetric way based upon A's measurement, you're still going to get a 50/50 response for yes/no questions asked of random entangled particles)
Feel free to comment, as I paste this on every misunderstanding of Bell's Theorem here, and I edit to make more clear each time.
The key difference between a bag of coins and a microscopic quantum system is that the contents of the bag before being observed is unknown, whereas the quantum state is actually indeterminate. By observing one entangled particle, you force the other to also take on a definite state. Read up on Bell's inequality for the experimental justification of this idea.
By observing one entangled particle, you force the
other to also take on a definite state.
Not knowing which placement has been done, you put one bag in your freezer, and drive across town with the other bag.
Then you ask yourself the question, or perform an experiment to tell you, "Which bag did the cat put all the coins in?", at which point you open the bag and find it full of coins or empty, determining the state of the bag you have, and the state of the bag in your freezer at home.
No problem, huh?
Except, if you'd asked a different question, or performed a different experiment, to tell you "Which bag contains all the copper coins, and which contains the silver coins?" - you would have still got a valid response, and found the bag either full of copper or silver coins, again determining the state of the other bag at home.
That's the nature of entanglement. Without knowing the state, the nature of the question you ask of one particle will determine what sort of answer you get, in a way that instantaneously affects the bag at home too. i.e. someone opening your freezer just after you ask your question will see the other bag in a consistent state with the bag you have.
That's why it's so gorram weird.
http://physics.stackexchange.com/questions/3158/why-is-quant...
http://physics.stackexchange.com/questions/126622/quantum-en...
Either you believe the state exists but is unknown, and
cannot be known until measured,
or, you believe that you know the state does not exist,
and materializes upon measurement.
If you're satisfied that their might be multiple past states which could all produce the same result, determining the current state, then you can safely ignore these semantic debates, about whether there is a concrete-but-unknown value, or whether the present value remains uninitialized and undefined.
It is a hack, so to speak.)
Imagine I'm flashing a light at you on and off, randomly. Some of the flashes aren't random and contain a message. To read the message, or even detect its existence, you have to know which flashes were random, and this is what observing both particles in an entangled pair allows us to do. There is no signal with only a single particle.
That said, the simulation argument strongly pushes in favour of a simulated reality - particularly when you consider that there is no need for it to be real time, or of the entire universe. In short if we ever gain the capability to accurately simulate a small corner of the universe, then it stands to reason that someone further up the hylaean flow (apologies to Stephenson) also has.
Hell, maybe the rotation of distant galaxies is off because they're just sprites ;)
So there's probably some other simulation of our universe where they tried to do models, but it was too slow.
If not, then the simulator introduced a pre-mature optimization. The existential ramifications of such a development inefficiency are palpable!
I think that fits the computation model and doesn't require an observer or operator.
[1]: https://en.wikipedia.org/wiki/Mathematical_universe_hypothes...
And, saying that it's a "mathematical structure" is just saying that it's a structure that humans can apply mathematics to model. So there's really no mechanism for this to be true, except in the trivial "the universe has structure" sense, which also tells you (basically) nothing, because humans can't even perceive things that don't have structure, nor can we reason about them.
I think you are getting hung up on the semiotics of mathematics which is indeed a human construct. The idea of "1 + 1 = 2" is true no matter how (or if) you represent the idea.
> saying that it's a "mathematical structure" is just saying that it's a structure that humans can apply mathematics to model
That's not what the theory says (AFAIK). The mathematical universe hypothesis says that there is nothing in the universe, it's all just mathematics.
Edit: Think about it this way: if you could simulate a universe and in that simulated universe you modeled people and all the stuff around them, what would you tell those simulated people with their simulated free well what a table is made out of? It's all mathematics, right?
AFAIK yes, the limits are known as Planck Constants. It means that we are living in a digital universe.
https://en.wikipedia.org/wiki/Planck_constant
There are also conjectures about a _holographic_ universe.
https://en.wikipedia.org/wiki/Holographic_principle
https://www.youtube.com/results?search_query=holographic+uni...
(Obviously you don't mean necessarily literally on paper)
Do you claim that the predictions that are made about what is observed are false, or that the interpretation is wrong, or?
Surely you don't mean that by interpreting it in a particular way, it causes different things to happen, so I can't think of anything other than those two.
What happens is:
- before observing one particle, observations on the other particle are described and predicted by an entangled, superposition, state.
- after observing one particle, observations on the other particle are described and predicted by a non-entangled, non-superposition state. The possible outcomes of the observations on the other particle, both predicted and measured, are different after the observation on the first particle.
Of course the observation causes a change in the state of both particles simultaneously. And I understand that strictly speaking, in the physical sense of the word, there is no 'action'. But does it really matter if people say they are 'acting on' the remote particle by observing the local particle, as long as they mean the exact same thing?
> after observing one particle, observations on the other particle are described and predicted by a non-entangled, non-superposition state.
This is the misleading part. It is not true in an absolute sense. It is only true for the observer that makes the "first" measurement (with "first" in scare quote because relativity). It is not true for the observer of the "other" particle. There is no measurement that can be made on the "other" particle that will tell you if the first particle has been measured.
> The possible outcomes of the observations on the other particle, both predicted and measured, are different after the observation on the first particle.
This too is misleading because it assumes that "possibility" is a universal property and it isn't. The "possible" outcomes for the "other" particle change for the observer of the "first" particle, but not for the observer of the "other" particle. And even this is not quite right because it depends on whether the observations are time-like or space-like separated, and whether or not there is a classical communications channel open between the two observers. It gets complicated. Read the paper.
No jokeprod paper or video is going to put it to rest. You sound like a religious nutcase.
And the difference between me and a religious nutcase is that I can back up my position with math.
tl;dr: Just because you have an equation doesn't mean that equation corresponds to anything real. This is the same mistake people make all the time with statistics -- the math is easy, finding the right math to use can be very hard.
https://www.youtube.com/watch?v=GdqC2bVLesQ
Being so sure about your position when it isn't proven is a pretty bad way to do science. You're essentially implying that 3/4 people on that stage are wrong or idiots. I don't buy it.
See blog.rongarret.info/2015/02/31-flavors-of-ontology.html for more details.
Of course that does make me think about forking processes and copy-on-write, and the idea that our reality is just a simulation in a computer and that maybe creating new universes is not as expensive as we might at first think...
I admit I'm still in the process of learning and figuring this stuff out.
> This is the crucial point that many discussions overlook
I agree completely with this (and have said as much in the past --https://www.reddit.com/r/cosmology/comments/2zy19s/bowling_b...) but
> The concept of "curvature of space" is obvious nonsense
This is emphatically not correct. Space can be curved without being embedded in a higher "meta-space". You can have a 2D surface that is curved as if it were the surface of a sphere without it actually being on an actual 3D sphere -- it just has to "connect up" the right way and have "parallel" lines bend towards each other and so on. Ditto in more dimensions.
This is not really true. If you take a flat two dimensional space, a sheet of paper, this space has no intrinsic curvature. You surely now imagine this sheet of paper laying flat on a table in front of you embedded in our usual three dimensional space. Now pick it up and role it to form a cylinder. This gives extrinsic curvature to the space, curvature in the space the sheet is embedded in. But the sheet has still no intrinsic curvature, if you were a two dimensional creature living on the sheet you can not tell whether it is laying flat on the table or is rolled up to a cylinder, at least ignoring the fact that the cylinder connects two opposite edges of the space.
The surface of the earth on the other hand has intrinsic curvature, angles of triangles don't add up to 180 degrees for example. And this intrinsic curvature is a feature of the space not of the embedding into a higher dimensional space. It is not easy to visualize if possible at all, but spaces can have intrinsic curvature independent or even without an embedding, our three dimensional space can be curved without being embedded in a higher dimensional space and the same of course holds for space-time.
These demonstrations with balls rolling on a stretchable rubber sheet to visualize gravity are really misleading in this regard because they use a good deal of extrinsic curvature to make things work but in reality mass doesn't deform space-time into a fifth dimension or at least it doesn't necessarily do so.
>The idea of "1 + 1 = 2" is true no matter how (or if) you represent the idea.
That's really a triviality, though. If you have the idea that 1+1=2, then yes, it's true. Usually people say mathematical theorems are true in "all possible universes", but the way they select which universes are possible is... by applying logic that works in this universe. 1+1=2 is only true because it doesn't contradict our experiences. It's useful. In another universe, it may not be useful, and thus wouldn't be true there.
>if you could simulate a universe and in that simulated universe you modeled people and all the stuff around them, what would you tell those simulated people with their simulated free well what a table is made out of?
I would put words in whatever order was most useful to them to employ for the construction and manipulation of tables. Anything else would be meaningless. You might as well just say "magic" if they can't use it.
Not quite. In the mathematical sense, 1+1=2 is true because (a) it is a well-formed sentence in a certain formal system and (b) there exists a proof of it in that formal system. The formal system consists of a grammar for well-formed sentences as well as rules for deriving true sentences.
The key point here is that the definition of "true" is part of the definition of the formal system. Unlike in philosophy, we have a clear and unambiguous definition of what "true" means, and its evaluation does not depend on properties of our physical universe.[0]
So when people say that "mathematical theorems are true in all possible universes", they're well-intentioned but I would argue that they are misleading. The deeper (philosophical) truth is that the (mathematical) truth of mathematical theorems is independent of universes[1].
[0] The fact that our minds are drawn to thinking about the specific type of formal systems that are usually considered to be reasonable foundations for mathematics may well be a consequence of the properties of our physical existence.[2] However, if by some magic the definitions of formal systems studied by alien civilizations in a different physical universe were to be transmitted to us, we would be able to arrive at the same conclusions about those systems as the aliens, and vice versa. There would be no disagreement about what sentences are true in such an alien formal system.
[1] Where I use the word "universe" in the physical sense and not in the sense that is found in set theory and its ilk.
[2] However, I personally don't think so. I believe (though I cannot prove it) that something like the Church-Turing hypothesis also applies to foundational formal systems at least up to basic set theory (possibly minus the axiom of choice). It is conceivable that some alien civilization in a much stranger universe would consider a certain extension of our set theory as the natural choice for mathematical foundations, but they would recognize our set theory as a subset of what they're studying.
Is your objection to the mathematical universe mostly that it's not useful to know everything is just mathematics? That our reality is essentially the same as if it were a simulation is just trivia but doesn't help you make a table?
Why should anyone care that it's mathematics? It's certainly not like any mathematics that we know; we can't do it some other way if we don't understand it. It's too big to fit in a brain, and too complex to simplify accurately. Since we don't understand its axioms, how do we know they form a mathematical structure?
Well, if the universe is a simulation, then you can start poking around for the limits of the simulation and finding out new things is something that lots of people enjoy.
http://www.technologyreview.com/view/429561/the-measurement-...
> When you "measure" the two halves of an EPR pair what you are really doing is performing two measurements on whatever system produced the EPR pair to begin with.
Here's the problem with that. Consider the measurements of a pair of space-like separated entangled photons. A choice can be made about the details of these measurements by the experimenters at the last second possible. For example, the rotation angle of a polarizer can be randomly chosen the instant before a photon strikes it, yet correlations with this choice show up in the other measurement that was taken far away. (Note that these correlations still don't allow you to send information faster than light.) But the "which angle" information was never contained in whatever system produced the two photons.
It's not true that no one denies this. Adherents of the Copenhagen interpretation deny it. They claim that measurement involves a non-unitary phenomenon called "wave function collapse."
> I can't quite tell exactly what you all are arguing about.
Exactly this. You may not realize it, but not everyone understands that measurement and entanglement are intimately related (in fact, the exact same physical phenomenon). In fact, some people vehemently deny it. There are even some card-carrying physicists who vehemently deny it.
> entanglement is not a phenomenon that can be explained classically.
That is certainly true (though I've met people who deny this as well).
> the aggregate system containing both continues evolving unitarily.
The Copenhagen interpretation is that the measured subsystem collapses in a non-unitary way. That doesn't imply the overall system did. I have no opinion* on whether a measured subsystem collapses unitarily or not — the answer to that question does not currently seem to be experimentally testable. But it is testable that the overall system continues evolving unitarily during a subsystem collapse (well, at least up until the overall system is measured), and this has been tested and verified many times.
(* Ok fine, I do have an opinion. I don't think unitarity breaks — ever. I think it appears to break through the process of decoherence. But I'm certainly not going to claim that as fact unless experiment can prove it somehow.)
http://arxiv.org/abs/quant-ph/9605002
(It's ironic, BTW, that you should complain that my citation is "not even a journal paper" when yours isn't either.)
And BTW2, Aaronson's blog post doesn't contradict my position. The Bell inequality violations are indeed real. They just aren't caused by "spooky action at a distance." They are caused by the classical correlations that arise when you trace over the quantum wave function of the universe in order to isolate a subsystem.
And BTW3, I actually did submit that paper to Physics Today back in the day. It was rejected, not because it was wrong, but because it wasn't anything new. (It's amazing how the Physics world bifurcates into two camps: those who think that the connection between entanglement and measurement is common knowledge, and those who adamantly deny that it is true.)
The fact that there are two legitimate camps means that no one knows for sure what is happening. And you are obviously in one of those camps. So to insist the world is a particular way is to deny how much is still unknown and acknowledged by others in the physics community.
So, to be clear: you are advocating some interpretation of quantum mechanics (for instance, but not limited to, the many worlds interpretation) where the measurement process is really measuring the system that produced the entangled pair?
I believe this interpretation fails to explain experiments where people have entangled particles with timelike separation [1], and then have shown that measurement of the second particle (which has never co-existed with the first particle in any reference frame) collapses the wavefunction of the first particle.
I'm not saying that the Copenhagen interpretation is the absolute truth, in particular many-worlds and superdeterminism are valid alternative interpretations, but I think the one you're advocating doesn't work.
[1] http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.110... (non-paywall: http://arxiv.org/abs/1209.4191 )
By measuring (one of the particles in) the system you are collapsing its wave function. Doesn't that mean the state of the system (both particles) is affected?
I don't have time to read that paper right now, but it sounds like simple entanglement transfer, not unlike what is done for "quantum teleportation." In any case, the math behind QIT is simply the math of QM, so anything that QM can explain, QIT can explain.
[UPDATE:] There was a published version of the C&A paper but I can't look it up right now (I'm on the road with very limited internet connectivity). But it turns out that the C&A position is essentially the same as decoherence/many-worlds. There is essentially no dispute over the facts any more. The problem is with the rhetoric in which those facts are wrapped. Even "many-worlds" is highly misleading.