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A Boost For Quantum Reality

Soulskill posted more than 2 years ago | from the superposition-of-super-positions dept.

Science 241

Eponymous Hero sends this excerpt from Nature: "The philosophical status of the wavefunction — the entity that determines the probability of different outcomes of measurements on quantum-mechanical particles — would seem to be an unlikely subject for emotional debate. Yet online discussion of a paper claiming to show mathematically that the wavefunction is real has ranged from ardently star-struck to downright vitriolic since the article was first released as a preprint in November 2011. ... [The authors] say that the mathematics leaves no doubt that the wavefunction is not just a statistical tool, but rather, a real, objective state of a quantum system."

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well, actually... (5, Funny)

notgm (1069012) | more than 2 years ago | (#39938039)

it is, and it isn't.

well, actually... (-1)

TubeSteak (669689) | more than 2 years ago | (#39938535)

it isn't, and it is.

Re:well, actually... (0)

Anonymous Coward | more than 2 years ago | (#39938697)

it is and/or it isn't...simultaneously

don't 4get: (1)

airdrummer (547536) | more than 2 years ago | (#39940117)

not is is not is not

Re:well, actually... (3, Funny)

jd (1658) | more than 2 years ago | (#39938647)

If you apply fuzzy logic, then it uniformly half-is.

Re:well, actually... (0)

Anonymous Coward | more than 2 years ago | (#39939585)

Haha, fuzzy logic.... it's not even main-stream. Go read some recursion theory.

Re:well, actually... (0)

Anonymous Coward | more than 2 years ago | (#39939359)

that that is is that that is not is not that that is not is not that that is is that not it it is that that is is also that that is not when that that is is part of a wave function

Add a little bit of punctuation and it all makes sense.

Re:well, actually... (3, Interesting)

pantaril (1624521) | more than 2 years ago | (#39939697)

Isn't there a way on slashdot to block "funny" comments? Those years old "jokes" littering almost each science-related thread have no value at all for me.

Re:well, actually... (1)

killkillkill (884238) | more than 2 years ago | (#39939849)

If you don't come here for the jokes, why do you? Certainly not the content anymore.

Re:well, actually... (1)

NEDHead (1651195) | more than 2 years ago | (#39940047)

you are all a bunch of half wits

Re:well, actually... (0)

Anonymous Coward | more than 2 years ago | (#39940087)

Well....yes and no.

Re:well, actually... (1)

pantaril (1624521) | more than 2 years ago | (#39940311)

It's kind of nostalgia i guess. The comments value is certainly droping over time but you can discover a hidden jewell from time to time.

Fortunatelly there is google+ taking over. With a nice science circle assembled, i can get my fix of science news and comments with good information value and without the usual slashdot comment spam.

Re:well, actually... (0)

Anonymous Coward | more than 2 years ago | (#39940071)

Yeah, sometimes I feel the same way. You can basically assign a negative value to funny comments and then adjust your viewing threshold accordingly.

Re:well, actually... (1)

c0lo (1497653) | more than 2 years ago | (#39939997)

the wavefunction is not just a statistical tool, but rather, a real, objective state of a quantum system.

I'm afraid the answer is more complex than that: unfortunately, the wavefunction has an imaginary part, stopping it short from getting real.

Hegel was half-right (2, Funny)

For a Free Internet (1594621) | more than 2 years ago | (#39938047)

Marx and Engels rescued the revolutionary, materialist core from the idealistic mysticism of Hegel's dialectic! Communism is our last best hope! Smash U.S. imperialism! Forge a revolutionary Leninist-Trotskyist workers party! Pizza!

Re:Hegel was half-right (3, Insightful)

caffemacchiavelli (2583717) | more than 2 years ago | (#39938095)

Maybe. No. Yes. No. Yes.

Re:Hegel was half-right (2)

mug funky (910186) | more than 2 years ago | (#39938491)

this needs an insightful mod at least.

Re:Hegel was half-right (-1, Redundant)

Jeremi (14640) | more than 2 years ago | (#39938637)

Maybe. No. Yes. No. Yes.

Nyes.

Re:Hegel was half-right (-1)

Anonymous Coward | more than 2 years ago | (#39938351)

Communist nazis. This is a job for McBain.

Re:Hegel was half-right (-1)

Anonymous Coward | more than 2 years ago | (#39938379)

I thought that's a job for Greek politicians.

Elephants! (5, Funny)

Black Parrot (19622) | more than 2 years ago | (#39938079)

the mathematics leaves no doubt that the wavefunction is not just a statistical tool, but rather, a real, objective state of a quantum system.

If that's the case, I would suppose that wavefunctions have wavefunctions.

Re:Elephants! (4, Funny)

snowsmann (313238) | more than 2 years ago | (#39938113)

It's turtles all the way down!

Re:Elephants! (1)

Samantha Wright (1324923) | more than 2 years ago | (#39938283)

(Fun fact: if you ever find someone claiming someone in particular had a conversation with an old man or woman that ended this way, they didn't do their research [wikipedia.org] . Probably.)

Re:Elephants! (0)

Anonymous Coward | more than 2 years ago | (#39939695)

So is it: "Elephant, Turtle, Elephant, Turtle, ... all the way down" or is it "Turtle, Elephant, Turtle, Elephant, ... all the way down"?

Re:Elephants! (1)

Black Parrot (19622) | more than 2 years ago | (#39938693)

It's turtles all the way down!

Uhm.. yeah. Sometimes I get my elephants and turtles mixed up.

Re:Elephants! (5, Interesting)

maxwell demon (590494) | more than 2 years ago | (#39938411)

the mathematics leaves no doubt that the wavefunction is not just a statistical tool, but rather, a real, objective state of a quantum system.

If that's the case, I would suppose that wavefunctions have wavefunctions.

Yes. That's known as second quantization.

Re:Elephants! (1)

Anonymous Coward | more than 2 years ago | (#39940039)

Yo Dawg! I heard you like wavefunctions, so I put some wavefunctions in your wavefunctions!

Whether or not it's technically correct (1)

Anonymous Coward | more than 2 years ago | (#39938083)

In practice applying the pop version of quantum theory to everyday life does result in a more cohesive and intuitive reality than trying to go with previous thoughts. It certainly does a better job of handling times when you have to reinterpret events when new information comes into play.

Emotional debate (4, Insightful)

mwissel (869864) | more than 2 years ago | (#39938087)

> The philosophical status of the wavefunction [..] would seem to be an unlikely subject for emotional debate

Well not to me. I guess any subject a given amount of people put lots of effort in can arise emotional debates. *Especially* if the subject in question is discussed philosophically.

Re:Emotional debate (2)

glorybe (946151) | more than 2 years ago | (#39938553)

I'm not certain people are quite done fussing over the reality of the flat Earth notion. That means that it may be a while before they are up to any arguments over quantum mechanics and the actuality of various realities. As for myself I'm still stuk on the fabric of space notions. What is the grid size of the fabric? How small a fish can swim trough the net? how many nets are there and do they hold a certain distance between layers. Are these fabrics in numerous colors? Are the fabrics laid out all over the universe equally? Will some company find a way to make me pay for my share of the fabrics of space? Maybe those fabrics exist to keep immortal souls from slithering out of this universe.

Re:Emotional debate (1)

jd (1658) | more than 2 years ago | (#39938661)

The Flat Earth debate only started in the 1800s, until then people had believed in this globe thing.

Re:Emotional debate (1)

maxwell demon (590494) | more than 2 years ago | (#39938747)

Actually I'm pretty sure that in the middle ages the vast majority of people had not even thought of the question.

Re:Emotional debate (2)

jd (1658) | more than 2 years ago | (#39938851)

Sailors heavily relied on the idea the world was a globe (it lets you measure distance on the open seas with no frame of reference) and it's a handy concept to have in deserts for much the same reason. By the middle ages (and even by the Classical era), a lot of art referenced a globe and that means even those with no direct experience or use for a globe would be aware of it by popular cultural reference.

Re:Emotional debate (0)

Dcnjoe60 (682885) | more than 2 years ago | (#39939999)

It was just a couple of weeks ago that a /. article talked about how the more analytical one was, the less religious one was, with the general consensus being that the more analytical one was, the more rational one was. Well, the study of quantum particles seems to be about as analytical as one can get. So an emotional debate seems to be about as rational as religious belief (at least according to the prior article).

maybe like this... (0, Interesting)

Anonymous Coward | more than 2 years ago | (#39938099)

and interesting image http://dequantified.net/preview/factorpreview.gif [slashdot.org]

Meh (-1)

Anonymous Coward | more than 2 years ago | (#39938169)

meh Meh MEh MEH MEHH eMeHH meeh meh um meh

I get it now (1, Troll)

slashmydots (2189826) | more than 2 years ago | (#39938187)

I can see how people could get so passionate over the topic. I myself passionately don't know what the hell they're talking about.

Re:I get it now (4, Interesting)

History's Coming To (1059484) | more than 2 years ago | (#39938629)

The argument used to be whether the wave function was "real" or whether it was a mathematical artifact, in other words is a particle actually smeared out or does it exist at one point and we're just limited in our observations of it (aka a "hidden variable"). These days the argument is whether the (Copenhagen interpretation) wave function actually exists or whether it's a mathematical artifact of a different theory, such as Everett's "Many Worlds" interpretation. Personally I go with Everett, but for philosophical/anthropic arguments rather than anything testable at the moment.

Re:I get it now (2)

Anonymous Coward | more than 2 years ago | (#39940237)

The problem with the many worlds interpretation is that if you flip a coin and it comes up heads, there must also be a world where the coin came of tails.... and one where it came up donkey, and one where the universe instantaneously collapsed, and one where the coin wasn't there at all, and one where the coin was exactly the same but one atom was at a slightly higher energy. And in all these more then infinite worlds, there would be events that require equally many universes to take on alternatives. Observing Occam's razor, it's simply not justifiable to invent more alternate universes then there are atoms in our universe times the number of femtoseconds our universe has existed, simply to explain away why an event that could be predicted accurately to fall in either of two cases, actually fell in one and not the other.

Heh (1)

Anonymous Coward | more than 2 years ago | (#39938189)

Reality is not a wave function. It's a useful model, but it's absurd to think of it as real and physical.

The cat isn't really both alive and dead. It's either still alive or it died. It certainly knows.

Reality is reality and models are models.

Re:Heh (5, Interesting)

steelfood (895457) | more than 2 years ago | (#39938221)

It certainly knows.

It knows, but you don't. You don't because you haven't measured it yet. And until you measure it, the answer is not the simplified version of the cat being dead and alive at the same time, but that there's a probability it's dead, and a probability it's alive, but it'll never be more than probability until you actually confirm it. Once you confirm it by measurement, the probability of one state goes to one, and the probability of the other state goes to zero.

This goes back to the age-old question: If a tree falls in a forest and no one is around to hear it, does it make a sound? It certainly makes a noise, but does it make a sound?

If there's nothing to observe reality, does it still exist? That's the essence of Schrodinger's cat.

Re:Heh (2)

jtownatpunk.net (245670) | more than 2 years ago | (#39938239)

If there's nothing to observe reality, does it still exist?

Yes.

Moving on.

I said moving on!

Re:Heh (4, Insightful)

Artifakt (700173) | more than 2 years ago | (#39938413)

I've never understood how some people can be so dogmatically sure about the existence of an objective reality. Not to say there isn't one. but I've actually heard some people claim that 100% of their own experience supports an objective reality external to themselves. That would imply that a persons dreams, hallucinations, emotions, being fooled by optical illusions, and other such things were all proof of something about the nature of that reality. A little bit of introspection here soon shows that, however convinced you are of there being an objective reality or however certain you are that your experiences support it, you simply can't, in reason, claim that every single experience you have proves something about the nature of that reality.
          Hell, most people don't learn that their 'self' is running on a physical substrate normally called a brain, until they are at least eight to ten years old. All those other experiences up until then certainly didn't reveal much about the underlying nature of any objective external reality until then, did they? That's a pretty damned important fact about the supposed objective external reality, considreing that brain will have litterally trillions of sensory experiences before it ever even possibly gets to a state where it can become aware of its true nature, and then only if it grows up in a society that has learned modern medicine.
        It amazes me still that so many people can think kicking a stone really refutes Bishop Berkeley.
        The evidence that QM is more than a mathematical trick mounts. It's worth noting that, at the beginning of the 20th century, most scientists weren't at all sure atoms were real and not just a mathematical convenience. It took Einstein's paper on Brownian motion to convert many scientists to the viewpoint that atoms were more than a convenient simplifying model. If this work holds up as well as Einstein's, it may be equally respected in the judgment of history.
     

Re:Heh (4, Interesting)

jd (1658) | more than 2 years ago | (#39938727)

Try this as a thought experiment. Imagine your brain and your DNA scanned into a computer. This is used to generate a simulated you. This simulated you is placed in a simulated room in which all the known laws of physics are simulated to a high degree of precision.

You are placed in an identical, but real, room. The two rooms are connected via a terminal (or, in the copy's case, a simulated terminal).

You and the simulated you can ask for any scientific equipment that can fit into the room. Both of you can conduct whatever experiments you like. The only requirement is a unanimous agreement between you, your copy and those running the experiment as to which of you is physical and which is virtual.

If no observation, experiment, or set of experiments, exists that can prove which is real, then you cannot prove what is "real" - there'd be nothing so unique to reality that would allow you to unquestionably establish that something belongs to reality and not to something else. If, however, you CAN through experimentation reach a unanimous verdict, then an objective reality is provable.

It is my opinion that it is the first case that would turn out to be true.

Re:Heh (2)

hawkinspeter (831501) | more than 2 years ago | (#39938783)

It'd be easy to distinguish the real and virtual "you"s. The simulated "you" wouldn't be able to run at the same speed as reality, so you just figure out which one is running slower.

Re:Heh (1)

johanatan (1159309) | more than 2 years ago | (#39938921)

That's only true if the machine running the simulation is not powerful enough. Given a local high-order maximum which exceeds the average 'reality' surrounding it would be enough computing power.

Re:Heh (2)

Mikkeles (698461) | more than 2 years ago | (#39939399)

With magic and woo, all things are possible.

Re:Heh (1)

hawkinspeter (831501) | more than 2 years ago | (#39939497)

I don't believe it will ever be possible to build such a machine within the constraints of the universe.

Re:Heh (0)

Anonymous Coward | more than 2 years ago | (#39940329)

It's not provably impossible (simulating a single room requires only a fraction of the computing power known to be possible within the known universe.)

Re:Heh (2)

dcollins (135727) | more than 2 years ago | (#39938881)

The copy will have additional breakdowns specific to the hardware it's running on (power failures, etc.), which will not be evidenced by the non-copy.

I think that Joel Spolsky would call this the "Law of Leaky Abstractions".

Re:Heh (4, Funny)

johanatan (1159309) | more than 2 years ago | (#39938927)

Not if it's running on the 'cloud'. Come on man, get with the times.

Re:Heh (1)

Anonymous Coward | more than 2 years ago | (#39939045)

This simulated you is placed in a simulated room in which all the known laws of physics are simulated to a high degree of precision.

Both systems would have "known knowns" and "known unknowns", but only the real system would have the "unknown unknowns".
Trying to simulate them would only create "known unknowns" as we would be building it upon the "known knowns" and our perception of unknown.
The moment we start guessing and making up the "unknown unknowns", we move away from the real system and our simulated system starts to become noticeably fake.
Our simulated "unknown unknowns" would fit in too perfectly to our current perception of the universe, as they would essentially be "known unknowns", waiting to become (be proven or disproven) "known knowns".
A box with a cat which is both alive and dead.

The "unknown unknowns" in the real system on the other hand would skip the "known unknowns" stage, becoming "known" instantly, but not necessarily fitting our current perception of the universe.
The box appears out of nowhere, we open it and find a cat inside.
Later on, a guy called Erwin comes along and tells us that the cat was both alive AND dead before we opened the box and we go "WTF? You crazy or something four-eyes?"

Re:Heh (0)

Anonymous Coward | more than 2 years ago | (#39939127)

easy you just described the experiment yourself,
have the copy's DNA scanned, and simulated within the simulation, recurse until the original simulation runs out of CPU (or recursion dept exceeded)

Re:Heh (0)

Anonymous Coward | more than 2 years ago | (#39939437)

Even the simulated room needs a reality. It's the reality of the computer doing the simulation. Yes, that reality looks very different from the simulation, but it nevertheless exists. Take away the computer, and there will be no simulation, and no simulated person which could ask whether there is a reality. Therefore the simulated person in the simulated room can tell there is a reality.

Re:Heh (0)

Anonymous Coward | more than 2 years ago | (#39939537)

Are you arguing that simlations does not exist in objective reality? Then you haven't understood the philosophical problem. Anything could exist in an objective reality, dreams, simulations aswell as physical objects. For a subjective truth to exist then it must be possible for two different entities to observ the same reality and see different results.

It is possible that one cannot differentiate between an objective reality and a subjective reality. I for one am convinced that some objectivity exists (I can prove to myself that "if this is a pen then this is a pen"), but I am equally convinced that there is a possibility that some of what I sense *could* be subjective, just aswell as it *could* be objective.

Re:Heh (1)

Dcnjoe60 (682885) | more than 2 years ago | (#39940175)

It would be easy to distinguish the real you. It is the one that would actually exist, since the entire premise of somehow scanning your brain and DNA into a computer is not possible. This scenario is like the question of "If God is all powerful, can he make a rock so heavy that he can't pick it up."

Re:Heh (1)

Jamu (852752) | more than 2 years ago | (#39940337)

Request a copy (or as many as is required) of the computer. Run it. The simulated version will run slow.

However this doesn't imply that objective reality is provable, just that computers can't simulate reality perfectly.

Re:Heh (3, Insightful)

billcopc (196330) | more than 2 years ago | (#39939139)

Given that I've spent the majority of my life working with computers, I've come to accept reality as just another theory. Does the OS know it's inside a virtual machine ? (without the hypervisor intentionally making itself known) How can any person know, with absolute certainty, that they're not a brain in a jar, being fed simulated input ? How can we even know we're a brain at all ? For all I know, my entire existence could be a work of fiction, the Internet could be a fabrication of my mind, along with all its inhabitants.

The only thing we can reasonably assume, is that thought exists.

(and yes, I think the best psych/philosophy profs were the ones who dropped acid on a regular basis :)

Re:Heh (1)

Dcnjoe60 (682885) | more than 2 years ago | (#39940207)

Given that I've spent the majority of my life working with computers, I've come to accept reality as just another theory. Does the OS know it's inside a virtual machine ? (without the hypervisor intentionally making itself known) How can any person know, with absolute certainty, that they're not a brain in a jar, being fed simulated input ? How can we even know we're a brain at all ? For all I know, my entire existence could be a work of fiction, the Internet could be a fabrication of my mind, along with all its inhabitants.

The only thing we can reasonably assume, is that thought exists.

(and yes, I think the best psych/philosophy profs were the ones who dropped acid on a regular basis :)

If you really think the OS or any other program knows anything about itself, you need help. The OS and programs are just electrons 0s and 1s. There is no sentience.

You can be reasonable sure that you exist if you can think (I think, therefore I am), because for thought to exist, some "thing" has to have the thought.

Re:Heh (1)

mr_gorkajuice (1347383) | more than 2 years ago | (#39939245)

I'd imagine that from the point of view of any die-hard extremist atheist, it becomes really really hard to make fun of religious nuts if your beloved science isn't even based on the assumption of the existance of an objective reality.

Re:Heh (1)

Bongo (13261) | more than 2 years ago | (#39939487)

I think the real trouble and problem comes up considering consciousness. The eye and brain are analogous to a camera with a lens, a CCD and a CPU processing images. A really advanced CPU could even start describing in words what it is looking at. But at no point does the camera experience the image it is capturing. That's the difficult issue with sentience. What is this ability to experience, as opposed to just mechanistically reacting by processing inputs and outputs? Why are we not just human robots, acting in an environment -- a sophisticated robot could act behaviourally in complex ways that match human complexity, yet would not require sentience, it can just process data on a high enough level -- but no sentience would be needed -- it would be 100% asleep, just a sophisticated "sleepwalking" robot -- so why do we, in addition to being biological human machines, also sentiently experience? And as you say, the hallucination starts right from the beginning, although we might not remember a lot, and who knows, at that point why limit the dream to one instant, or one day, or one lifetime? Our everyday consciousness is beyond weird. Yet the ability to create experience is the most basic nature of our existence. It isn't just "self-awareness" in the sense of having a mental concept of myself as a human with a name. It is sentience that is experiencing everything, whether I know my name or not. Plus, we seem to acknowledge that there are many many sentient beings, all experiencing their own hallucination but nevertheless, interconnected in some way, which is in some way the physical reality, even though, each of us only creates our own dream of that reality -- for is there an objective thing called "red" ? or is "red" a dream phenomenon, whereas in reality "out there" there is merely some sort of vibration -- so how does a vibration become "redness"? how do beings convert that vibration into experiences of "pink" and "red" and "the aroma of roses"?

Re:Heh (1)

Mr. Slippery (47854) | more than 2 years ago | (#39940221)

But at no point does the camera experience the image it is capturing.

Who says that a sophisticated enough camera, wouldn't?

That's the difficult issue with sentience. What is this ability to experience, as opposed to just mechanistically reacting by processing inputs and outputs?

Please demonstrate that you have this ability to experience and are not "just mechanistically reacting by processing inputs and outputs".

Re:Heh (2)

q.kontinuum (676242) | more than 2 years ago | (#39939553)

I just have to send the link here... It's so damn funny, and yet the only people able to appreciate it are probably those attending discussions like this :-)

http://www.smbc-comics.com/index.php?db=comics&id=2535 [smbc-comics.com]

Re:Bishop Berkeley (1)

Skybluedk (2635401) | more than 2 years ago | (#39939653)

I can't remeber the finer details of Berkeley's argument, but I really don't see his point.

Most likely the world exists as we perceive it. In this case he is just wrong.

In case that the world does not exist, but is just an illusion of some sort, then what? If noone else exists, theres no point in telling them? Let alone spend time on writing a book about it?

You might as well entertain the idea that the world just is. Maybe the illusion will be removed from your eyes and you will see the real reality later on, but discussing it here makes no sense at all to me.

Re:Heh (1)

Dcnjoe60 (682885) | more than 2 years ago | (#39940111)

I've never understood how some people can be so dogmatically sure about the existence of an objective reality.

Because not all religion requires a deity.

Re:Heh (4, Informative)

locofungus (179280) | more than 2 years ago | (#39938277)

It knows, but you don't. You don't because you haven't measured it yet.

No. Well, maybe for the cat, we're not able to do the experiment to tell.

But in the equivalent test using a photon in place of a cat and orthogonal polarization states in place of dead or alive, the photon most certainly does not "know" what state it is in.

This is the essence of Bell's inequality and the fact that there is no local hidden variable theorem compatible with the results of QM.

Tim.

Re:Heh (0)

Anonymous Coward | more than 2 years ago | (#39938291)

> Well, maybe for the cat, we're not able to do the experiment to tell.

Try it with a penguin. They have higher IQ than people on BBC.

Re:Heh (0)

Anonymous Coward | more than 2 years ago | (#39938305)

This goes back to the age-old question: If a tree falls in a forest and no one is around to hear it, does it make a sound? It certainly makes a noise, but does it make a sound?

OT, but there's a very interesting alternate analysis on this quote. It's a bit on the philosophical side and I'm bound to stuff it up, but it's something like this.

If an intelligent living organism (lets say a person), were to experience some physical sensation (e.g. pain), but "he" doesn't entertain a sense of self (this is the hard part explain) with concepts such as "hurting me/ damage to my body, etc", would "he" still suffer?

Re:Heh (-1)

Anonymous Coward | more than 2 years ago | (#39938311)

You're an idiot.

Re:Heh (2)

narcc (412956) | more than 2 years ago | (#39938317)

It's about what is, not what you know. That is, it's not that you can't know, say, a particular property due to some limit to our ability to measure it -- it's that the property doesn't have a definite state.

Why are people so desperate to believe that they live in some Newtonian billiard-ball universe? Hell, that didn't even work for Newton!

Re:Heh (0)

Anonymous Coward | more than 2 years ago | (#39940331)

"If there's nothing to observe reality, does it still exist? That's the essence of Schrodinger's cat."

No... The essence of Schrodinger's cat is that there are physical experiments (see Bells theorem) where you cannot explain the outcome if you assume that the cat was either dead or alive, it _has_ to be described throughout the experiment as being in a superposition until it's observed.

The philosophical question is more akin to: "If a tree that with 50% certainty has fallen and 50% certainty hasn't is passed through a polarizing tree splitter that always clogs if it's given a fallen tree, and never processes a tree that isn't fallen, does it process the tree?"

Naivly we say no, because if it's fallen it won't process, and if it isn't fallen then it won't process. Yet the world shows us that the tree is processed perfectly fine, since it is neither fallen or standing, and thus proves no problem for the polarizing tree splitter.

Re:Heh (1)

Dcnjoe60 (682885) | more than 2 years ago | (#39940095)

The cat isn't really both alive and dead. It's either still alive or it died. It certainly knows.

>

That's assuming there is a cat in the box to start with.

People need to chill, uniqueness is overrated (0)

FreeUser (11483) | more than 2 years ago | (#39940333)

Reality is not a wave function. It's a useful model, but it's absurd to think of it as real and physical.

The cat isn't really both alive and dead. It's either still alive or it died. It certainly knows.

Reality is reality and models are models.

Except that now we are finding the cat is both dead and alive. The question is, which universe do you inhabit? The only way for you to find out is to measure the result, collapse the probability, and determine which reality you inhabit. Your copy (the one you're so desparate to believe doesn't exist, perhaps because s/he threatens your sense of uniqueness, or free will, or whatever), if s/he opens the box and looks, will find s/he inhabits a universe with a different outcome.

As for self determination and uniqueness, this need not really trouble people. In an infinite set of universes, any outcome will be statistical in nature. Like predicting which atom will decay during the half-life of a radioactive material, no prediction can be made as to a particular state (or decision) you or I, as individuals in an indivual timeline, will make. We are still perfectly free to make decisions, and perfectly responisble for their outcomes, regardless of whether the decision we make matches that of 90% of our duplicates, or 0.0001%.

We may not be unique, but that doesn't mean we don't have free will. (Of course, we may not, but that doesn't follow from quantum physics, repetition in an infinite set, or any of the other variations of parallelism that appear more and more to be a fundamental property of our reality).

So people just need to chill, and see where the math and science actually take us. If it turns out we do inhabit a single, unqiue universe, then we get our uniqueness back and those bothered by parallelism are in luck (though it will be a short lived relief, geologically speaking, and ultimately fatal, astrophysically speaking). If it turns out otherwise, then so what? We still live our lives, with or without determinism. Whether we debate that in the context of a single unique timeline, or multiple, perhaps infinite timelines, doesn't really matter.

The only real loser is religion, whic presupposes just the one timeline. But then, religion has a long history of losing out to science and changing its teachings accordingly (like cockroaches, the memes don't die, they just adapt), so even that is unlikely to change if or when the multi-world hypothesis is proven.

So even the most dogmatic mind need not be threatened by either outcome...except perhaps for someone like the character in Star Trek, who is driven mad at the thought of another person in another universe just like them and spends eternity trying to hunt down and kill his duplicate. In which case, if reality is other than what they desire, tough shit.

How can it not be real? (0)

Anonymous Coward | more than 2 years ago | (#39938285)

If the wave function has an effect then it what way is it not real? Maybe its the mathematician in me but if reality can only be understood mathematically then I have no problem with that, thats just a problem with our imagination. I have always thought the divided universes interpretation of quantum physics multiple states was reading too much into things, a bit like during the steam age everybody wanted to interpreted things in terms of steam engines, thats useful, but the model implies things which the pure maths itself doesn't.

Re:How can it not be real? (3, Informative)

maxwell demon (590494) | more than 2 years ago | (#39938707)

If the wave function has an effect then it what way is it not real? Maybe its the mathematician in me but if reality can only be understood mathematically then I have no problem with that, thats just a problem with our imagination. I have always thought the divided universes interpretation of quantum physics multiple states was reading too much into things, a bit like during the steam age everybody wanted to interpreted things in terms of steam engines, thats useful, but the model implies things which the pure maths itself doesn't.

Think of probability distributions. If you throw a die and don't look at the result, you don't know which of the possible results happened. However you know that if you throw that die often enough, you know that each result happens approximately the same number of time. Therefore you can assign the same probability to each result, i.e. 1/6 each. But the probability distribution does not describe the current state of the die; the current state of the die is that it shows one of the numbers 1 to 6. It just tells you about your knowledge of that state; the equal probability just means "I have no idea which result happened, and there's no reason to favour either one."

Now assume that a trusted friend looks at the cube and tells you that it is not a 6. Now suddenly the probability distribution you assign to the cube changes: You'll assign probability 0 to the 6, and probability 1/5 to all other results. However the physical state of the cube does not change at all. Only your knowledge about it changes.

Finally you look at the die, and find e.g. it shows the 3. At that point the probability distribution "collapses" to the distribution which assigns 1 to the result 3, and 0 to all other results.

Now the idea of non-real wave functions is exactly like that. For those interpretations the wave function doesn't tell you what state of the system is, but only which results you get how often when you measure certain properties. When you measure, your knowledge changes, and therefore the wave function "collapses" just the same way the probability distribution "collapses" when you look at the die.

Re:How can it not be real? (2)

hawkinspeter (831501) | more than 2 years ago | (#39938811)

The problem with that analogy is that it can't explain the double slit experiment. How can you explain a single photon producing an interference pattern unless it goes through both slits simultaneously?

Re:How can it not be real? (1)

narcc (412956) | more than 2 years ago | (#39939005)

The 19th century mechanists that seem to dominate Slashdot can't explain it. Like creationists, they can't handle any science which doesn't conform to their preconceptions.

Re:How can it not be real? (1)

rufty_tufty (888596) | more than 2 years ago | (#39939231)

Maybe you understand it, maybe the GP does too, but are you saying the photon doesn't go through both slits simultaneously? It's fairly well accepted that a particle evaluates every possible path and the resultant path comes down to the derived probability for each possible end result.

How does this work?
Short Answer: Read up on QED.
Long (and probably incorrect because it's my understanding) Answer:
The way I get my head around this is to say consider everything as a field. The electron field, the photon field, the proton field (actually a composite quark field) etc.
However "things" only exist in discrete units. A photon on the double slit experiment starts as a quantum unit of energy emitted from an electron, propagates through the photon (em) field before finishing up as another interaction with an electron on the detector. As per QED the photon evaluates every possible path to the end point(easy to conceive if it is a field, but energy exists in quantum units). Where there are two holes there are paths that the wavefunctions can interact with each other and provide the interference pattern. Where there is one path the straightforward case applies where the photon (also consider it as a disturbance in the em-field) only interacts with itself so the rotation of the vector that you consider as you evaluate each possible path only evaluates to a minimum at the straight line case; whereas for two slits the photon rotation vectors have many probabilities about how the disturbances in the em field again interact with the electron in the detector.
Actually that's a rubbish explanation but I'm not Richard Feynman,,,

Re:How can it not be real? (1)

hawkinspeter (831501) | more than 2 years ago | (#39939507)

I think you've misinterpreted my comment. I'm saying that the photon goes through both slits (and all other possible paths). I was trying to point out that the gp's explanation of a rolled dice doesn't explain what is actually happening.

Arxiv.org link (4, Informative)

sugarmotor (621907) | more than 2 years ago | (#39938323)

Re:Arxiv.org link (0)

Anonymous Coward | more than 2 years ago | (#39938431)

Thank you so much, I was trying to have a glimpse of the real topic through the comments here and I was getting so desperate I was contemplating to pay 32$

It makes sense when compared to string (1)

Grayhand (2610049) | more than 2 years ago | (#39938389)

Most people think of matter as a solid when in fact there is no fundamental solid but matter is in it's base form a vibration which is roughly the same as a wavefunction. In some ways a wavefunction is no different a vibrating string so it's not as crazy as it sounds.

Re:It makes sense when compared to string (1)

reasterling (1942300) | more than 2 years ago | (#39938593)

I can cut a string. I can not cut a fundamental wave/particle.

matter is in it's base form a vibration

What is the thing that is vibrating? The equation E=MC^2 seems to indicate that matter and energy are just two expressions of the same thing. I acknowledge that my confusion "might be" just my inability to imagine nothing vibrating. That doesn't sound right. I mean "nothing" vibrating. See there, I have done it again. No matter how I say it it only makes sense if something is vibrating. If it is a thing that is vibrating then the vibration is just a property of the thing and is not the thing itself. Ripples propagate in a pond, but sound does not carry in a vacuum. If matter is only a vibration then the real question is what is the medium that the vibration propagates through. It seems to me that we have gotten right back to needing the "ether" to explain reality.

Re:It makes sense when compared to string (4, Interesting)

jd (1658) | more than 2 years ago | (#39938831)

I am not convinced that the particles regarded as fundamental actually are. I'm not even completely convinced that "particles" at that level even exist in the normal sense, since we know interference patterns exist when the gap is in time rather than in space. That makes no logical sense when using a corpuscular model.

It is my suspicion (IANAQMPBTIBO) that in precisely the same way that matter is merely energy that has "condensed" and entangled, particles are merely waves that have "condensed" and entangled. This is based on the fact that fundamental particles of the same type are totally interchangeable and no two particles of the same type are in the same state. To me, that does not appear distinguishable from saying that a single wave appears to be every particle of that type, since that would give you what is observed without having to have any new or excessively complex physics to explain it.

If that is correct, then neither space nor time are particularly important in QM. Which has been theorized by better minds than mine. You would be able to map everything into waveforms and not need spacetime for them to exist in. Rather, spacetime would be one way an observer could interpret those waveforms - it would be subjective, not objective. The waves themselves would be the only "reality". Again, there's a branch of QM based on just such a notion.

To answer your question as to what is "vibrating", in this line of thought there wouldn't be anything TO vibrate, per-se, no time for it to be vibrate in and no space in which the vibrations could take place. You'd simply have a multidimensional waveform where if you made some axis space and another one time, you could treat it as though something was vibrating. In practice, though, it would be a static n-dimensional waveform whose existence was logical rather than physical.

I like this particular branch of QM, as it means physics is a branch of mathematics, a specific group with specific properties and specific operations, and that the universe is a specific set of functions that wholly reside in that group. It makes maths the "ultimate" reality, which means these sorts of philosophical musings about the world can be answered through mathematical analysis (although maths permits that answer to be rigorously undefined).

Re:It makes sense when compared to string (1)

kwoff (516741) | more than 2 years ago | (#39938719)

And, like, an elephant is roughly like the earth, massive with a gooey inside, so it's not so crazy to think that Saturn is a whale wearing a tutu.

Negative... (0)

die standing (2626663) | more than 2 years ago | (#39938443)

I am a meat wavicle.

Non-relativistic QM is so 1920's... (1)

Takionbrst (1772396) | more than 2 years ago | (#39938497)

I don't get why people get so hung up on these aspects of QM... QM is NOT a complete theory anyway, and treating a particle as a localized field configuration (quantum field theory) neatly fixes many of the seemingly inconsistent aspects of non-relativistic QM (albeit while creating a thousand other problems/questions). It's ultimately irrelevant in some sense...

Yet another no-hidden-variables theorem (3, Interesting)

Anonymous Coward | more than 2 years ago | (#39938609)

The paper is related to Einsten-Podolsky-Rozen (EPR) paradox and the related "hidden variables" hypothesis which AFAIU states that there are some hidden variables apart from wave function that we can not observe directly. However, under some assumptions it can be proven that their existence affects some statistical properties of a particular type of measurements and therefore can be experimentally tested. One of such theorem was Bell inequalities published in 1964. In the Nature paper in question authors prove similar "no-go" theorem but under different assumptions. To quote:

The result is in the same spirit as Bell’s theorem[13], which
states that no local theory can reproduce the predictions
of quantum theory. Both theorems need to assume that
a system has a objective physical state such that prob-
abilities for measurement outcomes depend only on .
But our theorem only assumes this for systems prepared
in isolation from the rest of the universe in a quantum
pure state. This is unlike Bell’s theorem, which needs
to assume the same thing for entangled systems. Fur-
thermore, our result does not assume locality in general.
Instead we assume only that systems can be prepared
so that their physical states are independent. Neither
theorem assumes underlying determinism.

There is, however, another theorem by Kochen and Specker that is not cited in this paper but also does not assume locality. From wikipedia

The essential difference from Bell's approach is that
the possibility of underpinning quantum mechanics
by a hidden variable theory is dealt with independently
of any reference to locality or nonlocality, but instead
a stronger restriction than locality is made, namely
that hidden variables are exclusively associated with
the quantum system being measured; none are associated
with the measurement apparatus. This is called the
assumption of non-contextuality.

It would be interesting to know what would be the relation of results from the paper to that theorem...

If the internet has taught us anything (4, Insightful)

Intrepid imaginaut (1970940) | more than 2 years ago | (#39938725)

Its that there's no such thing as an unlikely subject for emotional debate.

Re:If the internet has taught us anything (3, Funny)

wonkey_monkey (2592601) | more than 2 years ago | (#39939027)

You take that back, you scruffy-lookin' nerfherder!

Thought (3, Interesting)

should_be_linear (779431) | more than 2 years ago | (#39938999)

Here is thought I had the other day: assume mathematical "function" that defines our universe and underlying physics (function that "theory of everything" is trying to find), works in _reverse_ direction of time. So that every particle (or whatever) at t is calculated from local state at (t+1). We usually thinks of laws of physics going in "natural" direction of time. Now, after the inevitable final end of intelligent civilizations in this universe, surely there will be some artifacts made by durable nanomaterials, that persists long after stars and even black holes evaporate into 'nothing". Universe calculated from backwards will therefore have such "intelligently designed" artifact at the _beginning_, as sort of input parameter, so it have to find a mathematically plausible way going forward (which is backwards in time for us) how these artifacts were created. Intelligent life and physical laws supporting intelligent life might be _result_ of something strange at the function input. That means if you have function where random "state" is input and set of equations ("laws of physics") is output, as soon as you put something looking improbable at input, say set of large prime numbers, function might find it is easier to create universe with intelligent civilization, which created this prime numbers, then to create universe where laws of physics created such improbable outcome by chance.

Re:Thought (2)

gshegosh (1587463) | more than 2 years ago | (#39939171)

You should read about CPT symmetry and breaking it. If you reverse time flow, you have to make some other changes to apply the same laws of physics.

Re:Thought (3, Interesting)

Anonymous Coward | more than 2 years ago | (#39939331)

Indeed, the problem with reversing time is that you suddenly have to change physics to handle the fact that the time has already been used. I remember Einstein expressing the view that we get 3 dimensions of space which can be reused and one dimension of time which can't be reused. And physics generally works and the equations are written for that reality. If suddenly, you can reused time and particles can go back and potentially interfere with themselves, then a ton of work would have to be put into making the equations work.

Summary (5, Informative)

FrootLoops (1817694) | more than 2 years ago | (#39939239)

The article confused me greatly so I read some of the arxiv preprint linked above. Here's the idea and context as I understand it. I've included some basic quantum background since most people here don't have it.

  * Intro to wavefunctions via an example. Electrons have a property called "spin" which has two states, "up" or "down". These can be measured in, for instance, the Stern-Gerlach experiment [wikipedia.org] where those electrons with spin up are deflected up by a magnetic field and those with spin down go down. The wavefunction corresponds to a list of the probability of each outcome occurring. The probabilities evolve through time via the Schrodinger equation which allows predictions to be made. One might prepare an electron where its spin wavefunction corresponds to the list [1/3, 2/3], so 1/3 of the particles go up and 2/3rds go down. [I've oversimplified; wavefunctions are actually elements of an abstract Hilbert space and complex-number amplitudes are used instead of real-number probabilities. I love Hilbert space but it's too much to explain here.]

  * Spin is not a classical property. One can measure spin "left" and "right" in addition to "up" and "down" by rotating the Stern-Gerlach (SG) device mentioned above and measuring left/right deflection. Suppose you run a stream of electrons through an up/down SG device which gives 80% of them "up". You then run those "up" electrons through a left/right SG device--it will always come out with 50% "left" and 50% "right". Even more strangely, if you then run the "left" electrons through another up/down SG device, the probabilities will now be 50%/50%, even though you selected only spin up electrons at the first stage so you'd expect 100%/0%. The act of going through the left/right device altered the spin up/down state somehow.

  * Hidden variables. Perhaps the electrons above have definite "spin vertical" and "spin horizontal" properties before the experiment starts. The act of going through a device must change the other property, though everything might be deterministic if there is some further hidden property controlling which electrons have their spin up/down states altered in which ways by passing through the "left" SG device. The alternative is that there are no definite properties which determine the wavefunction; the wavefunction is all there is, reality is somehow fundamentally probabilistic, and the wavefunction is "real" instead of a statistical construct.

  * Bell's theorem. Suppose spin up/down and spin left/right are definite properties and some hidden variables explain the above results. Using entanglement (which I'll leave undefined) and the assumption that information cannot travel faster than light, one can measure both the spin left/right and spin up/down values of a particle before the hidden variables have a chance to act (note: they might act in a very bizarre, perhaps even non-deterministic, manner, but we get to measure things before they have that chance). This gives a testable prediction which differs from quantum mechanics. If the experiment is performed, the "definite property" theory does not predict reality while the use of wavefunctions does predict reality. This is strong evidence for the reality of wavefunctions, though it's not completely conclusive.

  * The paper. It derives Bell's fundamental contradiction from fewer assumptions. In its own words,

The result is in the same spirit as Bell's theorem, which states that no local theory [i.e. one without faster-than-light communication] can reproduce the predictions of quantum theory. Both theorems need to assume that a system has a objective physical state L such that probabilities for measurement outcomes depend only on L. But our theorem only assumes this for systems prepared in isolation from the rest of the universe in a quantum pure state [e.g. a particle measured as spin "up" right after the SG experiment above]. This is unlike Bell's theorem, which needs to assume the same thing for entangled systems. Furthermore, our result does not assume locality in general. Instead we assume only that systems can be prepared so that their physical states are independent. Neither theorem assumes underlying determinism.

Dammit... (0)

Anonymous Coward | more than 2 years ago | (#39939851)

I made it almost through the second paragraph then googled "hilbert space". It's 8:15 and my brain already hurts. I should know by now to just email these to myself to read after work.

Contradictory (0)

Anonymous Coward | more than 2 years ago | (#39939421)

say that the mathematics leaves no doubt that the wavefunction is not just a statistical tool, but rather, a real, objective state of a quantum system

Isn't this an oxymoron?

of course it's real... (1)

mschaffer (97223) | more than 2 years ago | (#39940007)

Of course it's real. There isn't an imaginary term in the wavefunction equation.

About Time (1)

shawnhcorey (1315781) | more than 2 years ago | (#39940093)

It's about physicists got serious about quantum-wave physics. Thanks to the Copenhagen interpretation [wikipedia.org] , quantum-wave physics have been avoided by almost everyone. It's time for physicists to give up their religious beliefs and get on with it.

Carver Mead Interview (1)

ACE209 (1067276) | more than 2 years ago | (#39940097)

The Link in the comment of the article was quite interesting.
http://freespace.virgin.net/ch.thompson1/People/CarverMead.htm [virgin.net]
Basically stating that there is nothing statistical about quantum phenomenon and that Bohr got it wrong after all (to my limited understanding).

First step (1)

NEDHead (1651195) | more than 2 years ago | (#39940253)

I intend to patent the direct manipulation of the quantum wave function, which will, among other outcomes, be the basis for my infinite improbability drive.

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