Slashdot Mirror
Study Says Quantum Wavefunction Is a Real Physical Object
cekerr writes with this excerpt from an article in Nature
"The wavefunction is a real physical object after all, say researchers. ... the new paper, by a trio of physicists led by Matthew Pusey at Imperial College London, presents a theorem showing that if a quantum wavefunction were purely a statistical tool, then even quantum states that are unconnected across space and time would be able to communicate with each other. As that seems very unlikely to be true, the researchers conclude that the wavefunction must be physically real after all. David Wallace, a philosopher of physics at the University of Oxford, UK, says that the theorem is the most important result in the foundations of quantum mechanics that he has seen in his 15-year professional career. 'This strips away obscurity and shows you can't have an interpretation of a quantum state as probabilistic,' he says."
One of the stumbling blocks for learning this stuff at school was the people were hung up on the idea of "this-space", "that-space". It was a revelation to me that when they said "probability space" it was only a space in the mathematical sense (ie, something with N dimensions that could be graphed if N were not too large).
The way I saw it, people were prejudiced to believe that these were real spaces, the prejudice being that physics is strange at that level, thus there must be strange bizarre types of space. Nope. They were just things with N numerical characteristics.
Now you're telling me there really are strange spaces? That sucks.
"Abstract objects" or "mathematical objects" don't exist in general, so this suggestion is rather plausible. Of course, the reality of the wave function had been proposed before, but new arguments are sorely needed in philosophy of quantum mechanics.
--exa--
Can someone explain to me why having a wave function as a real object is less ridiculous then the alternative?
is that assault?
I swear they give me mod points to shut me up.
That there is uncertainty in the amplitude of the wave function too ?
Nullius in verba
This is what they have proven:
If a quantum wavefunction is purely a statistical tool, then quantum states that are unconnected across space and time are able to communicate with each other.
The rest is speculation.
IMO one observer's wavefunction is the other observer's statistical tool, where an observer is any ensemble of particles.
By the way, the wikipedia article on Bell's inquality stated something similar years ago.
Hey don't blame me, IANAB
Yes yes... Some amazing American innovation done at the ... Imperial college of... London?
They mean London, Arkansas, right?
I don't remember covering 'proof by claiming that something is unlikely' in my Physics degree.
Wasn't this hinted at by those oil-droplet-on-vibrating-medium experiments that partially reproduced the wave/particle duality?
dare step on my wavefunction, mister! Or I'll have to send my engevectors at you!
Where is that guy who'd die defending what I had to say when I need him?
Everything is physically real. Stored Information is physically real. Concluding something is physically real says nothing useful about what it is or its properties.
To quote spock "Nothing unreal exists"
So that's where he went after he left Dunder Mifflin. Impressive.
Lolz.
And your brain is just a switching device for different states of reality. This sentence branches into a hydra of different endings, including this one (this one) (this other one) (this other one). Maybe everything you imagine is actually image from realities;
THis MaGiC MoMent.
Sorry for this freaky post-- this version of me can't help but do what it does.
watching The Big Bang Theory?
by TheSpoom (715771) Uncaring Linux user here. I have nothing to add to this but please continue. *munches popcorn*
Next you'll be saying that neutrinos travel faster than light.
now that's meta
Yawn. Did these guys ever read Prince de Broglie?
http://galileo.phys.virginia.edu/classes/252/Bohr_to_Waves/Bohr_to_Waves.html
http://en.wikipedia.org/wiki/Louis_de_Broglie
A particle is a wave is a particle-wave; all we can say about the universe, is what we can say about the universe; there's no such thing as a "real physical object."
I would bounce this paper as a reviewer. It appears to be a recasting of Bell's Theorem, but it doesn't reference ANY of that work.
What's the difference? What is the difference between something being a "mathematical description of reality" and being real? I mean you can go back and forth between if numbers are real, etc. Have they discovered something "more real" than they previously thought?
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So does this support or refute the contention that reality is made up of a very very large number of universes constantly being created at each quantum step? Isn't that what the Copenhagen interpretation implied?
The universe is made from block transfer computations?
So, if I throw wavefunctions equations at friends is that assult?
No. They'll just give you a funny look and ask what kind of drugs you are on.
"We are just a war away from Amerikastan. When god vs god the undoing of man." Dave Mustaine
You have to be really careful with those "theorems". There are hundreds of Physicists with nothing better to do than come up with some new "theorem". The journals are full of them. Problem is, a lot of these theorems are based on very shaky premises and shaky reasoning. Even the great Von Neumann laid a really big egg in this very same area-- his "proof" was demolished, but not before it skewed research in this area for decades.
Whenever you require a probability function as part of a model, it means the model designer does not fully understand the process being modeled. However useful the model. Deal with it - we do not know everything yet.
I think the other possibility is just as fascinating, and possibly more impactful. The idea that all quantum states are related, even when not entangled. I'm certainly not a quantum physicist, but that seems like it would open amazing possibilities.
Ladies and gentlemen please look to the to the AC above. Observe the unrelated statements, the illogical statements, and the excessive long list of names being laid out for no particular reason, in a very non-slashdotesque manner.
Gentlemen, and ladies, we have ourselves an employee of the misinformation industry.
Gotta love quantum news posts: meaningless and meaningful at the same time, like a newspaper written by Schroedinger's Cat.
http://xkcd.com/849/
Copernican theory was picked up fairly quickly because it offered a simpler view of the cosmos. Astronomers bought into it largely because of its simplicity -- in effect, following Occam's Razor. It took until the early twentieth century for Einstein to say "you're all a bunch of doofuses: Ptolemaic theory is just as valid as Copernican, it all depends on your frame of reference." Thanks to relativity we now know beyond any shadow of a doubt that Ptolemaic epicycles are equally valid: they're just more complex. There is no privileged frame of reference. It is as true to say the Earth circles the Sun as it is to say the Sun circles the Earth -- it's just that the equations are neater in one frame of reference, not that they are correct. This bears repeating: according to special relativity, there are no privileged frames of reference.
Naively applying Occam's Razor to the question leads people to a false sense of certainty: they tend to think, "I've applied Occam's Razor, therefore I am likely choosing the better answer," without ever thinking, "did I formulate the question correctly in the first place?"
Don't get me wrong, I like Occam's Razor. But when people use Copernican-versus-Ptolemaic theories as an example of Occam's success, well... that tells me a quick lesson needs to be given on how Occam's Razor utterly fails in that case.
http://motls.blogspot.com/2011/11/nature-hypes-anti-qm-crackpot-paper-by.html
"Whatever way you choose to read the text [of the paper by Pusey et al], it makes no sense whatsoever. How they suddenly jump to the conclusion that there is a problem with the probabilistic meaning of the wave function remains completely mysterious."
To every physicist it is immediately clear that this paper is complete nonsense. I don't want to waste time disproving it here and will simply refer you to this explanation.
Wave function is a real object? You gotta be kidding. Next thing you will say "corporations are people". Oh! wait..
sed -e 's/Chuck Norris/Rajnikant/g' joke > fact
So, what I'm not getting is this: If a waveform is a real physical object and not just a conceptual statistical function, what is the physical nature of this object? Is it a half-dead Schodinger's Cat? Or is it a world where the Cat lived superimposed on a world where it died? Is it (gulp) both?
The result of the wavefunction is a correlated outcome within everything embarked within it.
It should be obvious this behavior can not be explained by an abstract statstical statement as it would not include correlated outcomes.
I have no idea what if anything useful TFA is trying to say.
I could go back a couple of centuries and make the same flawed logical argument - "as it is unlikely that the earth moves, therefore it MUST be the center of the universe."
The funniest thing is that this paper is coming out in the midst of the discussion of faster-than-light neutrinos. According to the interpretation presented in the article blurb at top, FTL neutrinos should be forbidden. If they actually exist, however, then that means that the quantum wave function really is a stastical thing and not a physical thing.
In the Nature blurb, there's a bit of discussion at the end that quantum states might all be linked, entangled or not.
In most physics classes, you learn quantum mechanics by calculating the interactions between isolated states. This thought process is natural and useful for certain areas of physics, but you end up worrying about hidden variables and how particles which are essentially in different universes can possibly communicate. This view does not need the wave function to be real, it can just be a statistical tool.
An alternative way of thinking about things is the idea that there are no isolated states (and no measurement apparatus which can exist outside the quantum system). From that point of view, one wave function is sufficient to describe the entire universe, traced back to the big bang. You don't need to worry about spooky action, everything obeys causality just fine assuming the wave function is real. There are some cosmological issues still, and it's not clear such a unified state is possible in an infinite universe.
At least we're starting to all agree wave functions are real and not just a statistical tool.
Stand by to see which theory Schrodinger's cat buries in his litter box.
Have gnu, will travel.
welcome our new theoretically physical quantum wavefunction-surfing overlords. time to crank up the Satriani.
I think it's great.
I think the wave function is a physically real object(*), and the randomness is not intrinsic or magically special but comes from thermodynamics and chaos, and, yes, Einstein was right: Copenhagen is a nonsensical load of bollocks.
More specifically that dice are not actually random in an ineffable sense, but their practical use has a sufficiently high Kolmogorov-Sinai entropy rate (roughly average amount of chaos generated per time) that they're random enough. In other words, quantum mechanics is regular physics, not mystical Copenhagen mumbo jumbo. Copenhagen works for computation, but that's because it's a very useful approximation for experimentally relevant circumstances, just like Fermi's "Golden Rules". Einstein was right, at least about the problem. His proposed solutions weren't, but the experimental evidence wasn't available until after he died and obviously he would have changed his mind given new results, because he was a physicist foremost and not a mystical philosopher.
Entanglement and uncertainty principle are not horse shit, because the central mystery of QM, that everything is operating in a Hilbert space still remains.
(*) To me, physically real means "acts as a source term in gravitation". This pretty clearly distinguishes "electrons/protons/photons" from "set of all sets of sets" crap and is as useful as any other description I know. Of course we don't have quantum gravity working yet but when we do it's pretty likely something like the wavefunction will be in there.
I saw the paper when it originally appeared on the arXiv. They claim to randomly prepare a pure state. This is a contradiction in itself, as von Neumann and others have already shown decades ago that random ensembles of states (or local parts of a globally pure state) have to be described by mixed states. If one uses the proper mathematical concepts, their results vanish immediately.
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The fact you called MWI "scientifically plausible" should be the first sign you don't have the first clue what you're going on about.
For MWI to be "scientifically plausible" it would have to make predictions which could be confirmed or falsified via experiment. That is, in essence, what science is: the subjecting of ideas to experimental test. (Go ask Zombie Feynman if you don't believe me.)
I've yet to hear any testable predictions MWI makes that would allow us to differentiate it from, say, Copenhagen. Maybe that's changed since I last dove into things (and if it has changed, I hope you'll tell me so), but I kind of doubt it.
David Deutsch is famous for saying that MWI is the only interpretation that gives any kind of sense to quantum computation. And, you know, I'm inclined to agree with him. That doesn't mean MWI is correct, though: it just means that the other interpretations do not satisfactorily explain those phenomena, not that MWI is the only possible interpretation that could give sense to quantum computation.
Also, given Copenhagen was first developed by Werner Heisenberg, it's kind of crazy to claim that Copenhagen is a "superstitious and completely nonsensical" interpretation. If I have to choose between exa on Slashdot being right when he says Copenhagen is superstitious and completely nonsensical, and Zombie Werner Heisenberg being right when he says that exa on Slashdot is misunderstanding Copenhagen, well... I'm going to side with Zombie Werner Heisenberg, you know?
I'd like to read the real paper or a sensible synopsis. THe problem with the news blurb is that the statements they quote and paraphrase seem to be completely at the (well established) Bell's theorem. Since they obvious know what Bell's theorem is this makes this even more of a puzzle.
Bell's theorem's implication is that their are not "hidden variable" theories that can explain quantum mechanics. That is, a lot of people would like to think that in QM maybe the photon does know which slit it's going to go through or does know it's moment and position at the same time, it's just that we can't ever measure that. THis would say the uncertainty of QM when there is no observer to collapse the wave function is fiction because it was in some specific state the whole time, it's just was hidden to us. Bell showed this cannot be universally true by preparing a wave packet and measurement that could not be explained by a single hidden state or a statistical mixture of pure states.
This article seems to be saying exactly the opposite. SO I think the article must be getting things horribly distorted.
Wavefunctions are not real objects, wavefunctions are holograms of real objects on a p-brane.
Non-local in 3-space is not necessarily non-local in n-space.
All of the mysteries of quantum mechanics are not so mysterious once you allow yourself to "see" beyond the confines of 3 space and 1 time dimension.
All they proved is that the simple statistical model is inadequate to describe why spooky-action-at-a-distance is not more commonplace.
David Deutsch is famous for saying that MWI is the only interpretation that gives any kind of sense to quantum computation. And, you know, I'm inclined to agree with him.
His understanding of quantum computation is also astoundingly flawed.
I'm sorry have I missed something, what does the term exists mean in this context?
Don't all ideas and mathematical constructs , including dreams exist? If they didn't we would not have words to describe them, because no one would ever have experienced them.
Is there some definition for the word exists that doesn't require recourse to metaphysics for it's definition?
I mean you might say occupies objectively measurable space time , but isn't that a pre-requisite for experimentally derived data?
âoeTolerance applies only to persons, but never to truth. Intolerance applies only to truth, but never to persons.
What a crappy summary and crappy article. The wavefunction is no more a real object than any other mathematical function. The statement: "f(x)=x^2 is a real object" has no valid meaning whatsoever. To even call it a theorem is ridiculous. Likewise goes for the wavefunction. It is a tool to model our "real" world. Some models are exact and precisely describe the "real" world. Other models only work under certain assumptions and/or reference frames.
If you actually read the research paper, the authors consider the question of whether a quantum state is a physical property attached to a system. Said another way, do quantum systems actually exist? Or are they purely theoretical? From the article:
"The statistical view of the quantum state is that it merely encodes an experimenter's information about the properties of a system. We will describe a particular measurement and show that the quantum predictions for this measurement are incompatible with this view."
The gist of it is that they have produced a result (didn't read the whole thing to actually figure out what their result was) which relied mainly on three assumptions:
Since their result is incompatible with the statistical view of quantum states, it must due to one of the assumptions above. They don't actually make the claim that quantum states are physical properties (like length, width, height, mass, etc. are). In fact, they conclude with:
"More radical approaches are careful to avoid associating quantum systems with any physical properties at all. The alternative is to seek physically well motivated reasons why the other two assumptions might fail."
Sure, but so is everybody's. I'd be a very happy man if my successes were half as brilliant as Deutsch's mistakes!
I blame the trend in the 90's of feeling it was unfair to the stupid children to point out they're stupid.
Now an entire generation thinks their beliefs are facts because their dimwit parents and teachers never pointed out to them that they were idiots.
I'm serious. Shows like Mythbusters dumb down the science, jump to conclusions left right and center, and re-enforce the belief that real science is boring so you need big explosions to keep people interested. Done right it would be brilliant - talking about the limits of their experiments and what other experiments would be needed to more confidently state whether something is a myth or not. Instead they do some limited testing and generalise, jumping to a conclusion as often as possible when there is nothing definite and reserving "plausible" for the rarest of rare cases when they really can't decide what's right or wrong.
Of course people here love Mythbusters and I'll be modded into oblivion, but the truth is when you teach that science is boring when it's not definite and things don't go boom, you get redneck generation.
These posts express my own personal views, not those of my employer
No, I mean his comments about quantum computation indicate that he really doesn't know what he's talking about compared to people who actually study quantum computation. He makes statements that are flat-out false.
Quantum computation isn't really that hard to understand. Quantum mechanics is somewhat unintuitive, but within the context of quantum mechanics, quantum computation is tricky, mathematically, but not difficult to understand.
The fact you called MWI "scientifically plausible" should be the first sign you don't have the first clue what you're going on about.
the wavefunction may or may not be real...But it appears that Dr. Sheldon Cooper is real!!
A bag is full of black and white marbles.
A child pulls out a marble, which proves to be black.
A quantum physicists draws a marble, which has a wavefunction that's a superposition of black and white states. He then examines it with a measuring device (his eyeball) and causes the wavefunction to "collapse".
"For MWI to be "scientifically plausible" it would have to make predictions which could be confirmed or falsified via experiment. "
That is a step in science. Something Feynman taught me when I was much younger.
""superstitious and completely nonsensical""
do you not understand what 'unwittingly' means?
The terms they used invoke a level of mystic thinking; which has spawned a whole field of woo.
BTW: It's starting to look like we will be able to test MWI. Which would bring use to the second step of the scientific process
The Kruger Dunning explains most post on
I'm unaware of these statements: can you give me a couple of examples, along with references that show these statements are false? I'd appreciate it a lot if you could.
A theory that does not make testable predictions is not well formulated, but that does not make it "implausible." There is no law of nature that guarantees that everything that is true must be testable by experiment. After all, mathematics allows for the existence of true statements that cannot be shown to be true. There is no reason why this could not be the case for physical reality.
It is reasonable to say that two theories that are reducible to the same mathematical description (in which case there is provably no experimental test than can distinguish them) should be regarded as the same theory, however different their verbal description might sound. And it can also be argued that a "theory" that has been proved mathematically to make no predictions at all (i.e. to be consistent with every possible outcome of every possible experiment) is meaningless (which is still not quite the same thing as implausible). On the other hand, it is important to distinguish between a theory that provably makes no testable predictions and one for which you have not yet managed to think of an experimental test.
What is real is the boundary, which is like a membrane that changes shape. This propagates through spacetime and collapses with an interaction. Interactions are time. This explanes the supra light speed of nutrino's, no interaction means the other boudaries will start running out of sync. There can only be boundaries and convolutions to make up our reality.
I realized this in 1994. It even got me laid.
"As that seems very unlikely to be true" since when has quantum mechanics bother with what we find likely?
This is not a question for science but for philosophy. You don't have to believe that the entities in a theory are real, especially if they are not directly observable.
The theory has certain elements, which may be fictional, makes predictions and gives rise to a model. If the model fits observable reality and the predictions are right, then the entities in the theory may be regarded as "real, physical" --- if you want.
I found it amazing and eye opening when i looked at a vibrations book and noticed the same basic equations as in my fields and waves class. That is when it hit me. Its all the same stuff! Why wouldn't it act in a similar manner. With that thought in mind, and with everyone talking about reality and thought. I would like to play with a thought experiment. Look at the similarities between thought that generates physical behavior and quantum physics. In my mind I can be anywhere and nowhere at once. Time distorts when in deep thought. Human nature can be as complex as anything I have ever experienced and can only be governed through probability. (if you don't believe me get married and have kids) I do not know if this has any real meaning, but getting out of the box once and a while is helpful.
Gentlemen, and ladies, we have ourselves an employee of the misinformation industry.
No, you silly person... we have a troll and/or very obviously tongue-in-cheek post.
If the former, it's because they know even an implausibly incompetent attempt at "propaganda" like that will be taken seriously and bitten on by someone.
A macroscopic particle (a drop) is bounded to a dynamic and local wave, both make an object which has exactly what de Broglie's theory is talking about.
Surely this is London, Ontario.
Seven puppies were harmed during the making of this post.
This comment spawned a universe where MWI isn't real!
It's no more real or less real than any model of a postulated external reality based on our sensory impressions and data, reinforced by reason-based statistical inference.
And how do you get sense impressions without sensor cells? And are the sensor cells "external", or is our awareness of them just a model of a postulated external reality?
.... if it can (maybe) be measured: Direct measurement of the quantum wavefunction
As acknowledged in the paper, their conclusion really is that IF measurement is a mysterious external process that collapses the wave function, THEN the wave function cannot be statistical.
But a simpler more consistent view is that measurement is any quantum process that results in correlating the state of the measurement device with what's being measured.
This view is 100% consistent with all of their quantum calculations.
But I am fairly certain that they forgot to carry a 1 somewhere.
Vote monkeys into Congress. They are cheaper and more trustworthy.
I guess you are trying to pursue an argument from authority. The only authority I respect is knowledge and intellect, and I don't think you have demonstrated much of either (by making an argument from authority most notably!).
Copenhagen interpretation is not favored much among physicists despite your claims. Maybe 50 years ago.
Copenhagen interpretation posits a hitherto unexplained event: "wave collapse", and even implies that this event is inexplicable, that it rests beyond the domain of physics. Thus, this is just a metaphysical farce. Bohr and Heisenberg probably were simpletons per philosophy, they must have held dualist views or they would not put forward this nonsense. Their interpretation is invalid scientifically prima facie, metaphysical statements can never be scientific.
As for your knowledge of philosophy of science, I don't think you know much either. Falsification is not necessarily required. Verification is sufficient to pursue a theory (induction). Falsifiable cases are icing on the cake in my opinion, and controlled experiments as such are very valuable in practice. Has testable predictions of any kind come from MWI meta-theory? I think it'd be fantastic to have it, but I don't think that this meta-theory, which seems roughly at the level of an interpretation or mathematical theory yet, is not logically unfalsifiable. How did you reach that conclusion, one wonders. And I don't think you've followed the recent publications on MWI either. It has far more credibility among physicists than you think.
On the other hand, if MWI is true (And I did not say it is, but it *can* be true unlike Copenhagen or the ultra-stupid Von Neumann interpretation which makes the dualism in Copenhagen explicit, again Von Neumann was a great mathematician and engineer, but unfortunately he was a frakking moron when it came to philosophy). Then, the wave function of the multiverse would be real, if *this* is true, and then, I think, this would mean that the world-line branches in the Everett multiverse would *not* be disjoint. In other words, perhaps this implies that the observations are not quite real, which would have strange consequences in interpretations.
Anyway, I am not an expert on the subject, but I happen to know the philosophical aspects quite well. You are welcome to offer a proof that MWI meta-theory is fundamentally unverifiable. So far, you have merely asserted such a thing with no citation, no argument, nothing at all. Is this how you conduct all your arguments? They are non-sequitor or very weak.
But yes, you would be a hero among the stupid dualists for defending such a mysticist interpretation, and since most people are idiots who believe in dualism, I think you would even find a fair audience! But to convince an actual philosopher, you have to do better than appealing to the idiocy of the masses.
Before you answer you might want to read this FAQ:
http://www.hedweb.com/manworld.htm
http://www.hedweb.com/manworld.htm#detect
Logically, if there is one thought experiment test of the theory, then, it is also possible to design a more feasible test. At least this seems to show that the theory is not logically untestable. I don't think an AI should be needed, Deutsch is probably flying too high there.
I sometimes like smartasses, but not always. Now, did you actually have an argument, or were you just regurgitating stuff you heard from your dim-witted friends at the faculty?
--exa--
It's an argument from Bayesian statistics, actually. Werner Heisenberg has a long, distinguished track record of highly creditable contributions to physics.
Your track record is unknown, but is exceedingly unlikely to match Heisenberg's. Doesn't take a genius to figure out which side I'm going to side on.
But, hey, being a philosopher makes you much better than a Nobel Laureate physicist who invented quantum mechanics, I guess, so -- bully for you.
With respect to Copenhagen having fallen out of favor, per Max Tegmark's paper "The Interpretation of Quantum Mechanics: Many Worlds or Many Words?", Copenhagen is the overwhelmingly preferred interpretation among working physicists, with MWI coming second. This is from a 1997 survey, so -- your claim that it's been out of favor for 50+ years is simply not true.
Einstein and Schrödinger also regarded the Copenhagen solution as effectively superstitious and nonsense. Bohr and Heisenberg won that round but they are loosing now, this paper shows that the Copenhagen interpretation is of necessity non-local something Einstein tried to prove with the EPR thought experiment. David Bohm and his supporters were prepared to loose locality to provide a hidden variables/quantum potential alternative to the Copenhagen interpretation, however I doubt the supporters of the Copenhagen interpretation and its modern variants are about to embrace non-locality.
Everett and quantum reality rules.
Whether Copenhagen is correct is not at issue. What's at issue is whether it's nonsense. The overwhelming opinion of working physicists, as evidenced by surveys asking which interpretation they subscribe to, is that Copenhagen is not nonsense.
The professor who taught me quantum mechanics summed it up like this: interpretations are our attempt to pretend that we know what the structure of knowledge is, and that we can use that metaknowledge to interpret the confusing world of quantum mechanics. The history of epistemology gives us very little cause to hope that we know anything useful about the structure of knowledge, though. Frankly, the only reason why physicists can philosophize on par with professional philosophers is that the whole of epistemology is bunk, and everyone operates on more or less the same level of bunk. Physicists should do physics and let philosophy attend to itself.
Now, I'm not saying I agree with his entire position... but I've definitely seen enough to make me sympathize with it. If I had to declare myself as an adherent of one interpretation or another, I'd say I belong to the Epistemology Is Bunk Interpretation.
That's precognition. Canada wasn't absorbed into the US until the resource wars of 2023.
Help stamp out iliturcy.
For those of you who, like me, have no idea what MWI means.
-- Cheers!
The interpretation of quantum mechanics is the ideal problem to apply Occam's razor. Since MWI is the simplest theory, it's probably the right one.
This reminds me of one of those incredibly cool proofs of God's existence, which roughly goes like this: "should god exist, he would be (by definition) perfect -- i.e. having all "positive" traits. Existence is a positive trait, so it is, by definition one of the traits of god. Q.e.d."
We certainly don't want the sitting tenants either.
Birds are not dinosaur descendants;birds are dinosaurs, for all useful meanings of "birds", "are" and "dinosaurs"
I struggled to read through the paper (rather than the misleading nature blurb).
The authors consider that either (i) the quantum state, |+> or |->, is equivalent to the physical description of the object, or that (ii) there is some other description which produces the outcomes of the quantum calculations, as if it was |+> or |-> say, statistically. They conclude that in (i) experiments are possible where the quantum magnitudes cancel each other, so say outcome of a certain measurement for <Q|+-> system is zero, while if (ii) was true than such scenario is not possible. Their paper is, basically, reminiscent of saying that, if light diffracted on a hole was a "probability" wave rather than "quantum" wave, then there would be no negative interference fringes, because probabilities cannot cancel.
I am pretty sure this paper will go out to trash after the first round of reviews, if it ever gets there. In a way, they do try to restate the Bell's Theorem, and there are no references to the Bell's theorem AT ALL ! Then yes, the states are prepared independently in their example, but are measured together, so THERE IS *entanglement* in fact ! The writing is very poor - they don't say clearly what the quantum scenario predictions are, what the "statistical" scenario predictions are, neither they even define clearly what the "quantum" or "statistical" scenarios are - their definition of "seismic" theorem basically comes down to "If the coin is flipped only once, there is no way to determine by observing only the coin which method was used. The outcome heads is compatible with both. The statistical view says something similar about the quantum system after preparation." Not to mention, finally, that any self-respecting quantum theory student did a calculation of the sort (probabilistic picture + negative interference of quantum states) in their late university years.
I can only feel sorry for the researchers at the Imperial College of London who apparently had been away from the developments in physics for the past 50 years since Bell's inequalities had been formulated and "hidden variables" and locality debate raged on. I can only suggest them to visit wikipedia before going ahead with submitting this paper, http://en.wikipedia.org/wiki/Bell_theorem. Also it is very frustrating that nature would publish a blurb like that, after the series of scandals regarding pubs in nature, such as about quite recent stem cell research "discoveries" in Korea, it really makes you think twice about what the hell their editors are thinking.
I'm not sure you are following me at all.
1. Have you presented any argument whatsoever that MWI is logically unfalsifiable? Where is that argument?
2. I am actually quite knowledgeable about Bayesian statistics. The mathematical formulation of quantum mechanics does NOT include any interpretation, that's why it's called interpretation in the first place. That you conflate Bayesianism with interpretations of QM is curious, as if Bayesianism supports any particular interpretation of QM, it does not do that! Bayesian vs. Frequentist debate applies to every application of probability theory. However, you seem to be, ignorantly, thinking that the epistemological interpretation in Bayesian statistics means that the probabilities in QM do not have an ontological character. This is wrong on so many levels. First, probabilities in QM are not identical to the wave function. You obtain the probability density function only after finding the square of the magnitude of the wave function right (by multiplying it with its conjugate)?. So, your statement is obviously meaningless, you are just another dualist talking about this religiously. Let me ask you: since you believe that , you also believe that there are non-physical things in the world, right? For Copenhagen and equally banal Von Neumann interpretations boil down to the claim that there are magical, inexplicable, non-physical "things" or "events" in the universe, along with what we consider to be real and physical (observations).
3. And have I said that this study supports MWI, or that MWI is my preferred interpretation? I did not. However, I do think that the notion of decoherence is much more scientifically plausible, as it does not contain vague, and unexplained pseudo-mechanisms like wave function collapse. The way I see it, "wave function collapse" is an inadequate attempt at explaining a real phenomenon, and it posits too much therefore it fails Occam's razor. It seems to be a behavioral description of a class of events actually, without revealing a consistent theory of "how", and that is quite suspicious in itself, however, yes, I anticipate that there would also be things that are incorrectly predicted by "wave function collapse". I do not find the rest of the Copenhagen interpretation problematic.
4. The issue of which interpretation is correct is the key to a GUT, therefore it has scientific significance. Good luck with starting from Copenhagen interpretation and obtaining a GUT! There are several plausible interpretations such as consistent histories, one of them could be true, but not Copenhagen or Von Neumann, which are fundamentally mysticist, it really is just medieval solipsism. Mystical stuff, especially solipsism, isn't physics. According to your celebrated Heisenberg, the particles aren't real but their appearance is real. This is just glorified stupidity, sorry.
5. I am equally suspicious about the everett interpretation of quantum computation, that quantum computers we construct harness the computational power of parallel universes. I suspect that as we build larger quantum computers we ought to be able to measure how much of this is true. Thus, perhaps this issue will be clarified during quantum computing experiments.
6. You also don't seem to understand that the reality of the wave function would not "destroy" Copenhagen interpretation, it would just change it slightly. Both observations and wave functions can be real in an interpretation. That subject is a lot more complex than you seem to think it is:
http://en.wikipedia.org/wiki/Interpretations_of_quantum_mechanics#Comparison
Philosophers of physics held many conferences on the subject, with apparently no real resolution, so if you just insist on this mysticist, semi-scientific interpretation go for it in your isolated space, but please stop preaching it to your students, and stick with math and experiments!
--exa--
I've yet to hear any testable predictions MWI makes that would allow us to differentiate it from, say, Copenhagen.
quantum suicide. But unfortunately you can't use this experiment to convince anyone but yourself of MWI, because it involves your death in most (but not all) world-lines.
Shor's algorithm is probably the best example.
In The Fabric of Reality, he says:
When Shor's algorithm has factorized a number, using 10500 or so times the computational resources that can be seen to be present, where was the number factorized? There are only about 1080 atoms in the visible universe, an utterly minuscule number compared with 10500. So if the visible universe were the extent of physical reality, physical reality would not even remotely contain the resources required to factorize such a large number. Who did factorize it, then? How, and where, was the computation performed?
His general view is that Shor's algorithm is performing the classical factorization computation but in parallel using quantum-mechanical superposition. (His argument from this is that the superposed states must map to alternative universes, but that's not really necessary to go in to.) This is a common but completely incorrect interpretation of Shor's algorithm. As far as I know, the only way to come to this incorrect understanding is to not really be familiar with how Shor's algorithm works, but just what its end result is. Shor's algorithm doesn't even really perform factorization, per se. It happens to be able to perform factorization in modular arithmetic space (which is the kind that is cryptographically relevant) because it turns out that you can turn modular factorization into a period-finding problem. Shor's algorithm is really just an efficient quantum-mechanical period-finding algorithm, kind of like a quantum-mechanical Fourier transform. None of what it does is mysteriously parallel. (I think Mermin's quantum computation book is a good source for understanding how Shor's algorithm operates. He also addresses, at least in some of the talks I've been to on the subject, common misinterpretations of quantum computation.)
I cannot add anything more insightful than what Matti P. has written at http://matpitka.blogspot.com/2011/11/are-quantum-states-only-figments-of.html er, maybe I could add to it, but I'm working on other theories... reality or non-reality does not matter...
If the wavefunction is a physical object, what are its physical dimensions?
I'm reminded of stories about researchers presenting proposals for physical theories, which were debunked by freshmen within minutes by means of dimensional analysis.
So, If the wavefunction is a physical object, what are its physical dimensions?
Well, I'm going with exa and David Deutsch, because they are right. Heisenberg was a revolutionary in his time, but this is not his time. Heisenberg was taught to think in classical terms, and he did that quite well. But we quantum mechanics simply cannot be made to exist in a single classical universe, unless we accept magical collapsing "wavefunctions" and a "god observer". These may have seemed quite plausible at the time, but now we know better. MWI is clearly the better interpretation.
If the wavefunctions are physical objects, what are the physical dimensions of the wavefunction?
If the wavefunction is a physical object, what are its physical dimensions?
Dead yet?