Is EVERTHING entangled?

[pallidin]

Given the hypothesis that everything that exists came from an original singularity, would it not follow, in physics, that everything is "entangled"?

I don't know, maybe I'm way-off here, but somehow it seems plausible.

[ZapperZ]

Given the hypothesis that everything that exists came from an original singularity, would it not follow, in physics, that everything is "entangled"?

I don't know, maybe I'm way-off here, but somehow it seems plausible.

If this is true, then entanglement phenomena would be so obvious that they would no longer be 'exotic' and that hard to show. But they ARE exotic and they ARE hard to show. So what does that mean?

It means that entangled properties are difficult to maintain coherently. Just because something started out being entangled doesn't mean that such a thing can be easily maintained. Long-distance entanglement right now can only be maintained by photons. Using particles are more restricted, both in time and distance, because such coherence are destroyed way too easily.

Zz.

[pallidin]

I appreciate your comment, Zapper; how you explained it makes this more clear to me.

[ueit]

If this is true, then entanglement phenomena would be so obvious that they would no longer be 'exotic' and that hard to show. But they ARE exotic and they ARE hard to show. So what does that mean?

I don't agree with this argument. First, entanglement appears pretty much in every chemical reaction, ionization, breaking of molecular bonds, etc. so it's not at all rare or "exotic". The fact that experiments showing correlations of entangled particles are difficult to do is irrelevant. Demonstrating gravitational interaction between two iron balls is also hard to do but this doesn't mean that such interaction is "exotic" or rare. It's also hard to "see" quarks but they are no less common than electrons.

It means that entangled properties are difficult to maintain coherently. Just because something started out being entangled doesn't mean that such a thing can be easily maintained. Long-distance entanglement right now can only be maintained by photons. Using particles are more restricted, both in time and distance, because such coherence are destroyed way too easily.

Those particles that interact with other particles from the environment become entangled with those. As the system becomes more and more complex, the experimental results cannot be interpreted in any meaningful way because of our lack of knowledge regarding the new, complex, system and computation limitation. However, this does not mean that entanglement disappears.

[ZapperZ]

I don't agree with this argument. First, entanglement appears pretty much in every chemical reaction, ionization, breaking of molecular bonds, etc. so it's not at all rare or "exotic". The fact that experiments showing correlations of entangled particles are difficult to do is irrelevant. Demonstrating gravitational interaction between two iron balls is also hard to do but this doesn't mean that such interaction is "exotic" or rare. It's also hard to "see" quarks but they are no less common than electrons.

But our "realization" of it is, i.e. we don't normally see such chemical reaction on the human scale that we identify as "entanglement". If it is, then we would see it easily and identify with it. Yet, we STILL consider quantum behavior as the behavior at the small scale, not the classical scale.

Those particles that interact with other particles from the environment become entangled with those. As the system becomes more and more complex, the experimental results cannot be interpreted in any meaningful way because of our lack of knowledge regarding the new, complex, system and computation limitation. However, this does not mean that entanglement disappears.

It has been shown that even ONE single interaction can destroy the coherence of a single-particle state. While that interaction results in a 2-particle state, it still has change the original state whereby the original single-particle coherent state has been destroyed.

The fact that we do not see, at the classical scale, all the quantum phenomena (and I deal with superconductivity, which Carver Mead claims is the clearest manifestation of quantum effects at the macroscopic scale), clearly shows that you can't simply carry those across from one scale to the next. You and I still do not know if the differences between the classical and quantum realms are simply separated by a crossover, or a "phase transition".

Zz.

[Naty1]

I,too, don't entirely agree with zapper. But entanglement does appear to be subtle.

While tehnically, correct, you don't EVER (no never) want to simply set aside a "thought nugget" because conventional physics hasn't gotten there yet. Zapper points out shortcomings based on current understanding....And those are legitimate insofar as they go.

The real issue is whether you believe your idea enough to find alternative explanations and experimental ways of verifying your idea...then you can claim Zapper and I were "shortsighted and myopic" in our thinking!!! The problem is focusing on those key thought experiments that lead to new solutions, not easy to do.

Roger Penrose has been working alrgely alone for many YEARS on twister theory and still can't get it completed.... If Einstein, also largely on his own theoretically, had not cast aside fixed space and fixed time which "everybody" knows was 'correct", special relativity would have been delayed.

I did some research on my own with 50 or 60 widely accepted conventional theories: ultimately all proved short sighted and most incorrect: the earth is flat, the earth is the center of the universe, orbits are circular, the universe is our galaxy, the universe is static, black holes are fictituous (these last two wrong ideas even sucked in Einstein) alchemy, atoms don't exist, there is an aether, there is man made global warming,etc,etc,etc

Let me offer an interesting alternative hypothesis: telepathy is due to entanglement! Unproven of course, but tantalizing!!! (not my idea, by the way)

And take your idea one step further: if our universe came from a random singularity then so did an infinite number of others...so not only is entangelment possible in our universe, maybe there is "entanglement" among all universes! Crazy, maybe, but if you consider a related hypothesis that gravity leaks to other dimensions...why not other universes....maybe via nearby branes that we are unable to detect (yet another hypothesis)...

[Fredrik]

I did some research on my own with 50 or 60 widely accepted conventional theories: ultimately all proved short sighted and most incorrect: the earth is flat, the earth is the center of the universe, orbits are circular, the universe is our galaxy, the universe is static, black holes are fictituous (these last two wrong ideas even sucked in Einstein) alchemy, atoms don't exist, there is an aether, there is man made global warming,etc,etc,etc

I was hoping that you were joking at first, but you seem to be serious. Anthropogenic global warming has definitely not been proved to be either of those things (shortsighted or incorrect), so you shouldn't be claiming that it has in a science forum.

[Doc Al]

Let me offer an interesting alternative hypothesis: telepathy is due to entanglement! Unproven of course, but tantalizing!!! (not my idea, by the way)

Alternative to what? Before you worry about "explaining" telepathy (using entanglement, no less), first you must demonstrate that it even exists.

[Naty1]

Telepathy is a stretch, in my book, but the discussion that went with it was interesting....
don't recall where I read it...

Entanglement, I thought, was generally accepted today, but is it rigorously verified...I don't know. ..but I don't plan on doing experiments anytime soon .

Brian Greene, for example, in Fabric of the Cosmos cites work by EPR, Bohm, Bell and Aspect and concludes:

Although the majority view holds there is a harmonious coexistence, some physicsts and philosophers consider the exact relationship between quantum mechanics, entangled particles and special relativity an open question.

It is amazing that these (quantum) connections exist and that in carefully arranged laboratory conditions they can be directly observed over significant distances. They show us fundamentally that space is not what we thought it was.

[Naty1]

Anthropogenic global warming has definitely not been proved to be either of those things (shortsighted or incorrect), so you shouldn't be claiming that it has in a science forum.

Perhaps, hadn't thought of it that way... yet, you make it sound as if it's a proven scientific reality: Should you be claiming such in a science forum...??

[ZapperZ]

Telepathy is a stretch, in my book, but the discussion that went with it was interesting....
don't recall where I read it...

Then you shouldn't even have brought it up. Explaining telepathy using quantum entanglement is a bastardization of QM. It is also crackpottery, which will NOT get you very far here in this forum if you've read the Guidelines.

I strongly suggest you halt this line of discussion.

Zz.

[Fredrik]

Perhaps, hadn't thought of it that way... yet, you make it sound as if it's a proven scientific reality: Should you be claiming such in a science forum...??
I didn't make that claim. It was you who claimed the opposite. I don't have the expertise to vouch for it personally, but it's clear that the evidence has convinced a vast majority of those who actually do research in that area. In my opinion that means that it's not inappropriate to say that AGW is real in a science forum. (It is however inappropriate to discuss this in a thread about entanglement in the quantum physics forum, so this will be my last post about this).

[ueit]

But our "realization" of it is, i.e. we don't normally see such chemical reaction on the human scale that we identify as "entanglement". If it is, then we would see it easily and identify with it. Yet, we STILL consider quantum behavior as the behavior at the small scale, not the classical scale.

Sure, quantum effects are not obvious at macro scale and I didn't say they are. What I want to point out is that this is not a valid argument against all particles in the universe being entangled.

It has been shown that even ONE single interaction can destroy the coherence of a single-particle state. While that interaction results in a 2-particle state, it still has change the original state whereby the original single-particle coherent state has been destroyed.

Yeah, but if the system is the whole universe there is nothing that could alter its state, right?

The fact that we do not see, at the classical scale, all the quantum phenomena (and I deal with superconductivity, which Carver Mead claims is the clearest manifestation of quantum effects at the macroscopic scale), clearly shows that you can't simply carry those across from one scale to the next. You and I still do not know if the differences between the classical and quantum realms are simply separated by a crossover, or a "phase transition".

I think that the classical world is a quantum world. We do not realize this because a macroscopic object is too complex to be described in terms of its constituent particles. So, we use statistics, and by doing so, we loose the interesting stuff.

[ZapperZ]

Sure, quantum effects are not obvious at macro scale and I didn't say they are. What I want to point out is that this is not a valid argument against all particles in the universe being entangled.

A "valid argument" is one that is supported by experimental evidence. You have none.

Simply claiming that the whole universe is entangled says nothing when you cannot show that. I'm sticking my left leg out. Show me the effect of that via entanglement. And no, I'm not being silly, because this IS the type of effects that we are asking for at the classical scale.

Yeah, but if the system is the whole universe there is nothing that could alter its state, right?

What state of the universe? You can actually write the quantum state of the whole universe? I'd like to see it please.

And why wouldn't it change? The entropy state can certainly very well change!

I think that the classical world is a quantum world. We do not realize this because a macroscopic object is too complex to be described in terms of its constituent particles. So, we use statistics, and by doing so, we loose the interesting stuff.

You don't know that, and at this stage, that is pure speculation. If we are speculating, then my speculation is as valid as yours. So what are we left with? Arguing about our favorite color?

Zz.

[gendou2]

If the system is the whole universe there is nothing that could alter its state, right?

There is nothing "outside" the universe.
If we decide that the universe started in one state, it must have spontaneously de-cohered and/or interacted with its self.
Because quantum states don't act like this (that I know of), I don't suppose the universe could have started out as a quantum state.

[gendou2]

The entropy state can certainly very well change!
Can you refer me to a text that explains this?

[ZapperZ]

Can you refer me to a text that explains this?

Er.. any text on Thermodynamics?

Zz.

[gendou2]

Er.. any text on Thermodynamics?

Zz.

I feel like a retard.

[schroder]

I wonder if gravity might be a form of entanglement. For all the trying, no one has detected the gravity wave or gravity particle, and if it was instantaneous, instead of propagating at velocity 'c' that could explain orbital mechanics more accurately.

[Hurkyl]

I wonder if gravity might be a form of entanglement...
Please don't clutter up thread with rampant speculation.

[Hurkyl]

I've seen you argue this before ZZ, but I've never really felt enlightened by your arguments. Maybe a historical analogy would help -- at what point in its development would you have considered the kinetic theory of gas to be credible? At what point would you have considered it favored above the alternatives? (Did it really have any credible alternatives?)

Now back to this one. What would have to happen before you consider "classical mechanics as an emergent property of unitary evolution, via decoherence" to be a credible theory of classical systems? What has to happen to consider it favored above the credible alternatives? Does it even have credible alternatives? If not, what about favoring it above its (noncredible) alternatives?

[schroder]

Please don't clutter up thread with rampant speculation.

Are you talking about This thread? The one which starts with the question “Is everything entangled”? And then it goes on to develop the idea of telepathy as a form of entanglement. And I am “cluttering” it up by mentioning gravity? A bit pompous on your part, don’t you think?

[Hurkyl]

Are you talking about This thread? The one which starts with the question “Is everything entangled”? And then it goes on to develop the idea of telepathy as a form of entanglement. And I am “cluttering” it up by mentioning gravity? A bit pompous on your part, don’t you think?
The presense of other clutter in this thread does not excuse your crackpottery. That post on telepathy was also inappropriate. (And, if you look, has already been decried)

However, "is everything entangled?" is actually mainstream science, being a question prompted by the behavior of unitary evolution (which, of course, is backed by oodles of experimental evidence).

[vanesch]

Should I stay or should I go ?

If I stay it will be trouble ...

If I go it will be double...

:cool: :tongue2:

Here we go again. Entanglement is a theoretical concept in quantum theory. Now, according to your favorite interpretation, and hence to your favorite "resolution" of the measurement problem, a measurement results in "irreversible entanglement" if you are of the unitary evolution crowd (the MWIers and so on), or results in "breaking up of entanglement" if you are of the projection crowd (Copenhagen etc...).

But both have the same observable consequences: quantum interference (the difference between the pure state and the mixture descriptions) disappear.

[ZapperZ]

I've seen you argue this before ZZ, but I've never really felt enlightened by your arguments. Maybe a historical analogy would help -- at what point in its development would you have considered the kinetic theory of gas to be credible? At what point would you have considered it favored above the alternatives? (Did it really have any credible alternatives?)

I don't know what "historical analogy" would have anything to do with this.

I'm a simple-minded experimentalist, not a historian. Maybe that's why the only thing I can "understand" is an experimental demonstration of what people are trying to sell. So if one is trying to sell that "entanglement is everywhere", then demonstrate to me that that entanglement is everywhere. It is THAT simple.

So far, I've shown why entanglement is NOT everywhere. I'll stand on my head, and see if someone else who's "entangle" with me would have the urge to want to assume the appropriate position.

Now back to this one. What would have to happen before you consider "classical mechanics as an emergent property of unitary evolution, via decoherence" to be a credible theory of classical systems? What has to happen to consider it favored above the credible alternatives? Does it even have credible alternatives? If not, what about favoring it above its (noncredible) alternatives?

That makes it even more of MY point. If classical mechanics is an "emergent property of unitary evolution, via decoherence", then by the definition of emergent property (per Laughlin and Anderson), then one CANNOT, in principle, derive classical behavior out of quantum theory. Period! More Is Different!

Zz.

[Hurkyl]

So far, I've shown why entanglement is NOT everywhere. I'll stand on my head, and see if someone else who's "entangle" with me would have the urge to want to assume the appropriate position.
You would make a mockery of the topic? :grumpy:

[ZapperZ]

You would make a mockery of the topic? :grumpy:

Don't change the subject and lump this on me. I said earlier that I was NOT trying to be silly in asking for such a thing.

I still want to see the empirical evidence (which no one has provided) to back up the claim that entanglement is everywhere. What has been made a "mockery" of is my request to support such a claim.

Zz.

[atyy]

I still want to see the empirical evidence (which no one has provided) to back up the claim that entanglement is everywhere. What has been made a "mockery" of is my request to support such a claim.

This isn't experimental evidence, but I'm curious what you make of their claim that the generic ground state of eg. their Eq 23 is entangled.

Entanglement in Many-Body Systems
Luigi Amico, Rosario Fazio, Andreas Osterloh, Vlatko Vedral
http://arxiv.org/abs/quant-ph/0703044

[Hurkyl]

Don't change the subject and lump this on me. I said earlier that I was NOT trying to be silly in asking for such a thing.
In response to the hypothesis that classical behavior is a by-product of unitary evolution, you demand evidence of non-classical behavior. In what way is that not being silly? :grumpy:

[ZapperZ]

This isn't experimental evidence, but I'm curious what you make of their claim that the generic ground state of eg. their Eq 23 is entangled.

Entanglement in Many-Body Systems
Luigi Amico, Rosario Fazio, Andreas Osterloh, Vlatko Vedral
http://arxiv.org/abs/quant-ph/0703044

That isn't a surprised. Note that in a superconductor, not only are the electrons making up a Copper pair entangled with each other, but ALL of the Cooper pairs that have condensed to form the long-range coherence are also technically entangled to each other. This is a very obvious example of a many-body system. Again, this isn't a surprised, nor is it anything new. As I've said earlier, Carver Mead used superconductivity as the clearest manifestation of quantum phenomena at the macroscopic level.

But note to what extent we have to do to preserve such coherence to be able to show quantum phenomena, i.e. it is NOT easy. Once you lose coherence, all traces of the obvious quantum effect are gone and we are left with our familiar classical world. So if a superconductor had to undergo a phase transition to get from the quantum to classical behavior, I'd say there's more than ample suggestion that the transition from classical to quantum realm isn't as trivial as everyone makes it out to be.

Zz.

[ZapperZ]

In response to the hypothesis that classical behavior is a by-product of unitary evolution, you demand evidence of non-classical behavior. In what way is that not being silly? :grumpy:

It is not silly when applied to the topic, something that you tried to point out.

So do you think EVERYTHING (capitalized in the topic) is entangled? If you do, forget unitary evolution or not (as if this is a done deal already in QM). Show me such evidence.

Zz.

[atyy]

But note to what extent we have to do to preserve such coherence to be able to show quantum phenomena, i.e. it is NOT easy. Once you lose coherence, all traces of the obvious quantum effect are gone and we are left with our familiar classical world. So if a superconductor had to undergo a phase transition to get from the quantum to classical behavior, I'd say there's more than ample suggestion that the transition from classical to quantum realm isn't as trivial as everyone makes it out to be.

That seems reasonable, but I don't understand whether that meshes with vanesch's characterization of decoherence as irreversible entanglement?

[ZapperZ]

That seems reasonable, but I don't understand whether that meshes with vanesch's characterization of decoherence as irreversible entanglement?

I don't know either, mainly because I've yet to be presented with compelling evidence of such "irreversible entanglement".

Remember that until Bell proposed his theory, most of the discussion on entanglement were nothing more than what most people are doing here - a discussion based on a matter of tastes. After Bell, at the very least, we have a way to empirically test one consequence of quantum entanglement (there are other "tests" that exploit other aspects of entanglement, such as beating the diffraction limit, etc). This now makes it into the realm of accepted physics.

I think by now, people should know me well enough that the only way to convince me of anything is via such experimental evidence. Till then, we are arguing about our favorite colors.

Zz.

[atyy]

I don't know either, mainly because I've yet to be presented with compelling evidence of such "irreversible entanglement".

But you would go with decoherence rather than say Copenhagen?

Edit: Well, I guess they're not mutually exclusive ...

[Hurkyl]

It is not silly when applied to the topic, something that you tried to point out.
I don't recall giving the tiniest suggestion of something so obviously contradictory.

[ZapperZ]

I don't recall giving the tiniest suggestion of something so obviously contradictory.

Fine, but you still ignore (and continue to ignore) the rest of what I had asked for. I can't believe that you care more about THAT than backing up your assertion with valid evidence.

Zz.

[Hurkyl]

Fine, but you still ignore (and continue to ignore) the rest of what I had asked for.
Yes, and intentionally. Originally, it was because I thought it pointless to have a discussion if you were going to caricaturize the topic. Now, I do so because I realize it's irrelevant -- I really don't understand how my desire to better understand why you are so vehemently opposed to the idea that classical systems might be described by quantum states turned into you demanding me to provide proof of said idea.

I can't believe that you care more about THAT than backing up your assertion with valid evidence.
Frankly, I'm appalled that you would think that I wouldn't care about being misrepresented like that. And just what assertion have I made, pray tell, that you would dispute? The most controversial that I can find is that things like MWI / Bohm are 'mainstream science'... but that doesn't seem at all controversial, and is incongruous with the demands you have been making.

[schroder]

The presense of other clutter in this thread does not excuse your crackpottery. That post on telepathy was also inappropriate. (And, if you look, has already been decried)

However, "is everything entangled?" is actually mainstream science, being a question prompted by the behavior of unitary evolution (which, of course, is backed by oodles of experimental evidence).

Frankly, I am appalled that you are appalled at being misrepresented, while accusing me of “crack pottery” for suggesting some connection between gravity and entanglement. For your information, investigation of such a connection is mainstream science, and has been for some years. I do not appreciate your charge of cluttering up this thread, and trying to link my comment with the earlier one on telepathy.
There are many papers in mainstream science concerning a possible linkage between gravity and entanglement, as well as quantum gravity.
Here is a brief excerpt from one:

If Bob falls into a black hole, he feels no acceleration and observes perfect entanglement with Alice. But if Alice fires a powerful rocket to accelerate away from the black hole and stay outside its "event horizon," she sees no entanglement at all.
Acceleration is linked to gravity through Einstein's general theory of relativity, so the result hints at a connection between gravity and entanglement, says Christoph Adami of the California Institute of Technology in Pasadena and the Keck Graduate Institute in Claremont. However, the tie between the two remains to be unraveled.

If you want the full text, here is the link:

http://http://www.sciencemag.org/cgi/content/full/sci;309/5742/1801a?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=gravity+%2B+entanglement&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT


But, be advised, you will need to log in first as a member of that crack pot organization, AAAS!!

[ZapperZ]

If you want the full text, here is the link:

http://http://www.sciencemag.org/cgi/content/full/sci;309/5742/1801a?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=gravity+%2B+entanglement&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT



Please note that you should give a proper citation (rather than just a link like this). This means author, journal, volume number, page number, and year.

Furthermore, the paper was actually published in PRL[1]. Adian Cho is simply writing a commentary in Science of the PRL paper.

Zz.

[1] I. Fuentes-Schuller and R. B. Mann, Phys. Rev. Lett. 95, 120404 (2005).

[schroder]

Please note that you should give a proper citation (rather than just a link like this). This means author, journal, volume number, page number, and year.

Furthermore, the paper was actually published in PRL[1]. Adian Cho is simply writing a commentary in Science of the PRL paper.

Zz.

[1] I. Fuentes-Schuller and R. B. Mann, Phys. Rev. Lett. 95, 120404 (2005).

Thank you for the correct reference

[vanesch]

I don't know either, mainly because I've yet to be presented with compelling evidence of such "irreversible entanglement".


The point is that there are TWO ways to explain *conceptually* the *same* observational phenomena. One way is to say that "entanglement stops", which can be interpreted as saying that we switch to a statistical mixture of product state description, which can then in a second step be re-interpreted as a classical description (there's still a distinction between both, in that individual subsystems can still be in non-classical states, but the entanglement between subsystems seems to be gone: we have a product state). The observable consequence of this is that one cannot obtain any quantum interference effects in the CORRELATIONS between observations on the different subsystems.

But the other way is to say that the "entanglement is now irreversibly enlarged with the environment". Well, the observable consequence of this is ALSO that one will not obtain any quantum interference effects anymore in the CORRELATIONS between observations of ONLY the two subsystems (and not of the miriads of "subsystems" of the environment).

In other words "everything entangled" and "end of entanglemetn" are observationally equivalent. They are just two conceptually different ways of thinking about how things behave. They are FAPP observationally indistinguishable. So asking for *experimental proof* for one or the other is an impossible request.

One shouldn't confuse "entanglement" with "quantum interference effects". In fact, entanglement SUPPRESSES low-order interference effects, to show them in higher-order correlations. And with irreversible entanglement with the environment, that means then that the ONLY potentially observable quantum interference effects will happen in the n-point correlation functions with n very large, meaning: impossible to observe. We can't observe 10^20-point correlation functions.

How does this come about ?

Let's look at a toy example:

We have 5 quantum systems in our toy world: S1, S2, S3, S4, and S5.

Let us assume that we prepared system S1 in a non-classical state (a superposition of "classical" states |S1A> and |S1B>).

Our "universe state" is now:

{ |S1A> - |S1B> } |S2X> |S3Y> |S4Z> |S5U>

It is a product state, in which we can consider the 5 systems independently. But, by JUST doing a measurement on system S1, we can find quantum interference, if somehow we find a measurement setup that measures |S1A> + |S1B> versus |S1A> - |S1B>.
Indeed, "classically" we would expect this to be 50% 50% (if we assumed that the system was a 50% / 50% mixture of S1A and S1B). And we will find 0% and 100%. That DEVIATION from the statistical mixture is a quantum interference phenomenon. It is the fingerprint of quantum effects.

Assume now that system S1 interacts with system S2.

We now have the universe state:

{ |S1A> |S2A> - |S1B>|S2B> } |S3Y> |S4Z> |S5U>

Well, if we NOW do the mesurement on S1 with the |S1A> + |S1B> versus |S1A> - |S1B> measurement device, we will find: 50% and 50%. The quantum signature 100% - 0% is gone. The system S1, BY ITSELF, doesn't seem to show ahy quantum behaviour anymore.

However, if we do a quantum CORRELATION experiment between system S1 and S2, and we check for "AA" versus "BB" results, we will find 50% AA, 50% BB, 0% AB and 0% BA. That still corresponds to a mixture, but if we start doing Bell-type experiments on the double system S1 and S2, we WILL find quantum interference effects, which show up here as violations of Bell's inequalities for instance. Or simpler: a measurement on the state:
{ ( |S1A> - |S1B> ) (|S2A> - |S2B> ) - ( |S1A> + |S1B> ) (|S2A> + |S2B> ) }
= - 2 |S1A> |S2B> - 2 |S1B> |S2A>

would yield 0 while we would expect, if we would have a statistical mixture: 25% (one should normalize the states).

This deviation from the statistical mixture prediction indicates a quantum effect, but notice that now, it only appears in 2-point correlation functions (between S1 and S2). It doesn't appear anymore in any measurement that you can do on S1 alone, or on S2 alone.

Now, let us suppose that we have the 5 systems entangled:

|S1A>|S2A>|S3A>|S4A>|S5A> - |S1A>|S2A>|S3A>|S4A>|S5A>

It takes more algebra, but you can find out that you will not find any deviation from any measurement that only takes into account 1, 2, 3 or 4 of these 5 systems. Each of these individual measurements, or 2-point correlations, or 3-point correlations (say, between S1, S2 and S3), or 4-point correlations (say, between S1,S2,S3 and S4) will be indistinguishable from the "mixture" case. BUT there will now be an observable interference effect in the 5-point correlation function (the measurement on |S1A>|S2A>|S3A>|S4A>|S5A> + |S1A>|S2A>|S3A>|S4A>|S5A> will yield zero, while we expect it to be 50%)

As our toy universe doesn't have more than 5 subsystems, 5-point correlation functions describe every thinkable experimental outcome. So "entanglement forever" will be equivalent to "no entanglement anymore" for 1, 2, 3 and 4-point correlation functions, but for 5-point correlation functions, we WILL see the difference.

In our universe however, there are many many more subsystems.

[Count Iblis]

So, ZapperZ's position is similar to only believing that the interior of a star is really millions of degrees of Kelvin if someone can measure it using a thermometer.

[atyy]

I wonder whether ZapperZ's demand for "experimentally verifiable entanglement" and "collapse entanglement" can be found in one of these different definitions, eg.
On experimental procedures for entanglement verification
S.J. van Enk, N. Lutkenhaus, H.J. Kimble
http://arxiv.org/abs/quant-ph/0611219

[ZapperZ]

So, ZapperZ's position is similar to only believing that the interior of a star is really millions of degrees of Kelvin if someone can measure it using a thermometer.

A thermometer is so 1950's already! I haven't used a thermometer at work to measure a temperature since I was in grad school!

One can make a very good estimate of something, even indirectly. But at least, there's SOME experimental justification for it, rather than just hand-waving argument. One can make a very good argument for the existence of the Higgs, but yet, we STILL want to make as direct of a verification as we can. This is because even if it is there, its true properties still need to be pin down. Look at what happens with the top quark. I accept that it exists, but do you think its presence was "directly" measured as directly as using a thermometer?

So what's the difference between that, and this one here? Why would I accept the evidence for the top quark, but not for everything being entangled? Are there any compelling evidence to point to the latter, which is what I've been asking for all long (and with zero response)? I'm not even asking for a "direct" evidence.

I also want to point out how difficult it is to demonstrate the Schrodinger Cat-type states at a "macroscopic" level. The Delft/Stony Brook experiments were not trivial, and they had to use superconducting device to enable them to preserve the coherence of the system.

So if superpostion, which is an essential "ingredient" in entanglement, is already THAT difficult to demonstrate as a system becomes larger, how easy do you think we can get quantum entanglement, which is even harder? Is my demand for evidence unjustified?

Zz.

[Count Iblis]

The fact that it is so difficult to perform these experiments involving macroscopic superpositions is precisely because of fast decoherence. The theoretical predictions on decoherence rates have been confirmed in these experiments.

Then because there are no well motivated alternative theories out there that propose some form of non unitary corrections to time evolution that becomes large on the macro or meso scale, I don't see where the extreme scepticism about applicability of quantum mechanics to the macro scale comes from.

[atyy]

But doesn't decoherence still need collapse? I understand decoherence as irreversible entanglement gives the preferred states into which collapse occurs, but doesn't actually predict any collapse. Or we could have MWI, but isn't MWI versus Copenhagen a matter of taste?

[vanesch]

But doesn't decoherence still need collapse? I understand decoherence as irreversible entanglement gives the preferred states into which collapse occurs, but doesn't actually predict any collapse. Or we could have MWI, but isn't MWI versus Copenhagen a matter of taste?

You got it. In the end it is a matter of theoretical, philosophical and esthetical taste.

I could think this to be somehow similar to the question whether classically, the universe is "Newtonian" with several particles in a single 3-dim space, or whether the universe is a Hamiltonian phase space in which we trace out a single world line.

Now, historically and intuitively, we would opt of course for the "Newtonian" view. Theoretically, we might be inclined to think more of a phase space thing. There's no way to distinguish between them experimentally.

The analogy is not perfect, because the Hamiltonian and Newtonian views are *strictly* equivalent, while the "everything entangled/MWI/..." versus the "collapse/no entanglement/..." are only equivalent for all practical purposes.

[ueit]

I could think this to be somehow similar to the question whether classically, the universe is "Newtonian" with several particles in a single 3-dim space, or whether the universe is a Hamiltonian phase space in which we trace out a single world line.

Now, historically and intuitively, we would opt of course for the "Newtonian" view. Theoretically, we might be inclined to think more of a phase space thing. There's no way to distinguish between them experimentally.

I think that the experimental evidence strongly favors the Newtonian view. We cannot observe phase spaces and world lines. We can observe, however, particles moving in a 3D world. In order to claim that what we observe is not real you need to redefine what "real" means, explain how is that that our brains are interpreting the phase space as particles, etc. I have yet to see such an explanation. Needless to say, this is also strongly against Occam's razor. Also, I don't see how can you find the Hamiltonian of a system without presupposing particles and forces, another reason to reject this view as a fundamental one.

I see no reason at all to not accept that "reality" is what we observe it to be.

The analogy is not perfect, because the Hamiltonian and Newtonian views are *strictly* equivalent, while the "everything entangled/MWI/..." versus the "collapse/no entanglement/..." are only equivalent for all practical purposes.

Same objections apply here.

[ZapperZ]

The fact that it is so difficult to perform these experiments involving macroscopic superpositions is precisely because of fast decoherence. The theoretical predictions on decoherence rates have been confirmed in these experiments.

Then because there are no well motivated alternative theories out there that propose some form of non unitary corrections to time evolution that becomes large on the macro or meso scale, I don't see where the extreme scepticism about applicability of quantum mechanics to the macro scale comes from.

What about from..... observation!, or lack thereof?

Zz.

[vanesch]

I think that the experimental evidence strongly favors the Newtonian view. We cannot observe phase spaces and world lines. We can observe, however, particles moving in a 3D world. In order to claim that what we observe is not real you need to redefine what "real" means, explain how is that that our brains are interpreting the phase space as particles, etc.


In fact, you are correct, there is experimental evidence for the 3D view, but it doesn't come from the Newtonian side. It comes from the relativity side, where the concept of locality is introduced. The purely Newtonian view with "action-at-a-distance" would rather favor the Hamiltonian approach, in fact, although there would still remain the issue of why this more general Hamiltonian structure is nevertheless restricted to the special case of "several particles in 3D" instead of "one universe-particle in 3N-D".
As to why our brains interpret things this way and not that way, that's entirely open to speculation I'd say.


Needless to say, this is also strongly against Occam's razor. Also, I don't see how can you find the Hamiltonian of a system without presupposing particles and forces, another reason to reject this view as a fundamental one.


It is not necessarily against Occam's razor, after all a single phase space and a single world line seems to be conceptually simpler than a lot of stuff of different kinds interacting through a lot of different interactions. After all, a single world dynamics is conceptually simpler than many individual dynamics and interactions, no ?
As to how to "find" the Hamiltonian through presupposing particles and forces, that's because we have to start from our (maybe totally deluded) descriptions which our brains prefer to state in 3D visions. So we have to use that "interface" to go from an observed situation to the "deeper reality" behind it, if we take on that picture. The fact that we have to do that dirty conversion work in the setup description and in the interpretation of the results is then just using the "window through which we see the universe".

Now, if you think I'm nuts even proposing this, then think of the holographic principle http://en.wikipedia.org/wiki/Holographic_principle where space is actually an illusion resulting from a 2-dimensional universe.

[ueit]

In fact, you are correct, there is experimental evidence for the 3D view, but it doesn't come from the Newtonian side. It comes from the relativity side, where the concept of locality is introduced. The purely Newtonian view with "action-at-a-distance" would rather favor the Hamiltonian approach, in fact, although there would still remain the issue of why this more general Hamiltonian structure is nevertheless restricted to the special case of "several particles in 3D" instead of "one universe-particle in 3N-D".

Non-locality is not a general feature of Newtonian mechanics, only of his theory of gravity. We know this theory to be incorrect so I wouldn't use it as evidence for anything.

As to why our brains interpret things this way and not that way, that's entirely open to speculation I'd say.

If we accept the 3d space +particle view there is no room for speculation because we simply define "reality" as what we observe. There is no need to interpret anything, just use the experimental data, directly into the theory.

It is not necessarily against Occam's razor, after all a single phase space and a single world line seems to be conceptually simpler than a lot of stuff of different kinds interacting through a lot of different interactions. After all, a single world dynamics is conceptually simpler than many individual dynamics and interactions, no ?

The Hamiltonian formalism is not against Ockham's razor but the necessary translation between the proposed reality and what we observe is. As you said, it's only a speculation. If what we observe is what we put into equations there is no need to explain the observation. But if we observe a thing and the theory says it's an illusion, then you need to explain how such an illusion appears, assuming that the theory is true. If you cannot provide this explanation then you have to make an additional postulate and this is against Ockham.

As to how to "find" the Hamiltonian through presupposing particles and forces, that's because we have to start from our (maybe totally deluded) descriptions which our brains prefer to state in 3D visions. So we have to use that "interface" to go from an observed situation to the "deeper reality" behind it, if we take on that picture. The fact that we have to do that dirty conversion work in the setup description and in the interpretation of the results is then just using the "window through which we see the universe".

Exactly what I've said above. Isn't it better to deal away with the assumption that our brains are deluded and with the necessary "conversion work" and simply say that what we observe is what it really is?

Now, if you think I'm nuts even proposing this, then think of the holographic principle http://en.wikipedia.org/wiki/Holographic_principle where space is actually an illusion resulting from a 2-dimensional universe.

It makes sense to make additional postulates if you gain some explanatory power. I'll take a look to that link

[WaveJumper]

As to how to "find" the Hamiltonian through presupposing particles and forces, that's because we have to start from our (maybe totally deluded) descriptions which our brains prefer to state in 3D visions. So we have to use that "interface" to go from an observed situation to the "deeper reality" behind it, if we take on that picture. The fact that we have to do that dirty conversion work in the setup description and in the interpretation of the results is then just using the "window through which we see the universe".


I couldn't agree more. We don't see the whole picture, that's how/why the newtonian world arises from space phase in our brains. It's our peculiar, limited and "coarse" sensory apparatus that brings about the notion of 3D vision.

[WaveJumper]

Exactly what I've said above. Isn't it better to deal away with the assumption that our brains are deluded and with the necessary "conversion work" and simply say that what we observe is what it really is?


For the experiment - yes, but there would be no newtonian world if there were no living forms.

[vanesch]

Non-locality is not a general feature of Newtonian mechanics, only of his theory of gravity. We know this theory to be incorrect so I wouldn't use it as evidence for anything.


It was an analogy. Nor Newtonian mechanics, nor Hamiltonian dynamics is "ultimately correct". I was using it as an example, an analogy which might make the essence of what I want to say clearer.

What I wanted to say was that there can be different points of view, different theoretical approaches, which are observationally entirely equivalent, and in that case, one cannot ask for experimental discrimination between those different viewpoints (as they are equivalent: exactly, or "FAPP"). There are reasons to prefer one over the other viewpoint, but these reasons are based upon aesthetic, theoretical and philosophical preferences themselves. So at the end of the day, it is a matter of taste.


If we accept the 3d space +particle view there is no room for speculation because we simply define "reality" as what we observe. There is no need to interpret anything, just use the experimental data, directly into the theory.


Sure. But then one might be seduced by the Hamiltonian viewpoint too, for more theoretical grounds. So it is a matter of priority in your tastes. One might be marvelled by the mathematical structure of Hamiltonian dynamics and simplectic structures, and prefer to look upon things that way. Or one might prefer to remain as closely as possible to one's "senses".


The Hamiltonian formalism is not against Ockham's razor but the necessary translation between the proposed reality and what we observe is. As you said, it's only a speculation. If what we observe is what we put into equations there is no need to explain the observation. But if we observe a thing and the theory says it's an illusion, then you need to explain how such an illusion appears, assuming that the theory is true. If you cannot provide this explanation then you have to make an additional postulate and this is against Ockham.


Again, it depends. You might prefer the unifying view and the mathematical coherence of the Hamiltonian approach, and consider that what you win in "postulatedness" there, compensates for the extra price of introducing an interpretation of experienced observation. Again, that depends on the value you give to each, and we're back to square one: it is a matter of taste.


Exactly what I've said above. Isn't it better to deal away with the assumption that our brains are deluded and with the necessary "conversion work" and simply say that what we observe is what it really is?


That depends what is the price to pay on the theoretical side. If you have to give up a great mathematical structure for that, it is open to discussion. It's a matter of what you consider "better".

[ueit]

I couldn't agree more. We don't see the whole picture, that's how/why the newtonian world arises from space phase in our brains. It's our peculiar, limited and "coarse" sensory apparatus that brings about the notion of 3D vision.

Do you have any evidence for this assertion? How exactly does the 3D world "arise" in a brain? What is the reason you feel the need to assume this?

there would be no Newtonian world if there were no living forms

Why?

[ueit]

It was an analogy. Nor Newtonian mechanics, nor Hamiltonian dynamics is "ultimately correct". I was using it as an example, an analogy which might make the essence of what I want to say clearer.

OK.

What I wanted to say was that there can be different points of view, different theoretical approaches, which are observationally entirely equivalent, and in that case, one cannot ask for experimental discrimination between those different viewpoints (as they are equivalent: exactly, or "FAPP"). There are reasons to prefer one over the other viewpoint, but these reasons are based upon aesthetic, theoretical and philosophical preferences themselves. So at the end of the day, it is a matter of taste.

When I look at a billiard ball I see, guess what, a billiard ball. I don't see a phase space. I would call this a great observational difference.

Sure. But then one might be seduced by the Hamiltonian viewpoint too, for more theoretical grounds. So it is a matter of priority in your tastes. One might be marvelled by the mathematical structure of Hamiltonian dynamics and simplectic structures, and prefer to look upon things that way. Or one might prefer to remain as closely as possible to one's "senses".

Nobody stops you to use the formalism that is more appropriate to the problem you have. As long as you cannot deal away with the "senses" (because otherwise you cannot relate the theory with observation) the beautiful Hamiltonian formalism must necessarily supplement them, not replace them. Therefore, it goes against Ockham.

Again, it depends. You might prefer the unifying view and the mathematical coherence of the Hamiltonian approach, and consider that what you win in "postulatedness" there, compensates for the extra price of introducing an interpretation of experienced observation. Again, that depends on the value you give to each, and we're back to square one: it is a matter of taste.

No it's not a matter of taste. You cannot replace anything from the "old stuff". To calculate the Hamiltonian of a hydrogen atom you need the assumption of a 3d space, point particles, coulomb force and so on. You cannot remove this stuff completely because you cannot calculate anything. So, above all Newtonian physics you ADD the Hamiltonian calculation.

That depends what is the price to pay on the theoretical side. If you have to give up a great mathematical structure for that, it is open to discussion. It's a matter of what you consider "better".

Why do you feel the need to assume that a mathematical structure, even if nice, must be real? You can use it anyway.

I think that you don't fully realize how big an assumption this "brain translation" is. This is not a simple postulate, like say the particle distribution in Bohm's interpretation. That is a simple and mathematically clear assumption about how 1D particles are placed in a 3d space. Only geometric primitives involved. You are making a claim about how a huge, complex system (the brain) works. Not only this is open to inconsistencies (may be your assumption contradicts energy conservation or some other physical constraint) but is a way to bring other assumptions throug the back door (a kind of cheating). I've read for example some so-called deductions of Born postulate from decision theory. But all this assumes already that a reasonable brain exist and that such a brain functions according to Born postulate. Circullar reasoning in the end, but well hidden.

[Count Iblis]

But doesn't decoherence still need collapse? I understand decoherence as irreversible entanglement gives the preferred states into which collapse occurs, but doesn't actually predict any collapse. Or we could have MWI, but isn't MWI versus Copenhagen a matter of taste?

I think that people who advocate Copenhagen should explain where the non-unitary effects that would lead to collapse which are not present in the dynamical laws are coming from and how it can be detected.

With only unitary time evolution, you can explain how a mass of, say, one gram in a superposition of two Gausian wavepackets that are separated by, say, 1 cm rapidly evolves into a mixed state of Gausian wavepackets (of the width of the thermal de-Broglie wavelength) if you take the interactions with the environment into account.

Then if this picture that does not have a fundamental collapse leads to objections because it leads to a Many Worlds scenario and people don't like that, then it is up to these people to explain how the theory should be modified and support that with experimental evidence.

I do understand that the debate on this issue will be going on, but what I don't understand is the extreme scepticism against the idea that you only have unitary time evolution without a fundamental collapse. This is the minimal hypothesis that, as far as we can check, fits all experimental data, while the fundamental collapse idea requires new physics for which there isn't a shred of evidence.

[ueit]

I do understand that the debate on this issue will be going on, but what I don't understand is the extreme scepticism against the idea that you only have unitary time evolution without a fundamental collapse. This is the minimal hypothesis that, as far as we can check, fits all experimental data, while the fundamental collapse idea requires new physics for which there isn't a shred of evidence.

The unitary evolution, by itself, does not explain our observations. We never observe superpositions. Therefore you need an additional postulate that explains how is that we see point particles in a 3d space and not a smoothly evolving universal wavefunction. IMHO it is this postulate that is hard to accept, and for a good reason.

[Count Iblis]

The unitary evolution, by itself, does not explain our observations. We never observe superpositions. Therefore you need an additional postulate that explains how is that we see point particles in a 3d space and not a smoothly evolving universal wavefunction. IMHO it is this postulate that is hard to accept, and for a good reason.

The additional postulate you need is simply the definition of observer states. The fact that the fundamental Hamiltonian contains local interactions takes care of superpositions that are widely separated in position due to decoherence.

You cannot expect that a fundamental theory would tell you how to define an observer. The best you could do in theory is to use the thoery to compute what an observer, put in by hand but defined in the language of the theory, would evolve as he interacts with the rest of the universe.

[WaveJumper]

I couldn't agree more. We don't see the whole picture, that's how/why the newtonian world arises from space phase in our brains. It's our peculiar, limited and "coarse" sensory apparatus that brings about the notion of 3D vision.

Do you have any evidence for this assertion? How exactly does the 3D world "arise" in a brain? What is the reason you feel the need to assume this?


I am not assuming anything, quite simply the morphological structure of your sensory apparatus is painting a limited and somewhat distorted picture of reality. Have a look at it this way:

People think objects are at rest when every particle they are made of is in constant motion at immense speeds. People think objects are made of "stuff", when solid objects feel solid because of a force called electromagnetism. Switch off electromagnetism and the strong nuclear force and the otherwise "solid" looking objects will disappear. People think solid objects are solid and physical when even the biggest physical thing they have ever seen in their lives - the Sun will disappear into a zero dimensional "point" without a trace if it were to hit a black hole. This event would seem mind boggling only because people usually think of "solid" matter from the perspective of their everyday lives at the newtonian level. But that's an abstraction created by the mind and the inputs of our "coarse" sensory apparatuses at our level of existence.
People think the universe is lit when in reality it's fundamentally dark. We've "picked" one wavelength of the EMR spectrum and "learned" to use it to find our way in the dark, but fundamentally there is no light and the universe is dark. It's lit only to us, who have this peculiar human sensory apparatus(and to the animals that have vision).
At the fundamental level, the universe is much different to what we think of it, due to the way we see it. Had we used neutrinos instead of photons for our vision, we'd see only extreme light and empty space. Neutrinos can pass through your body, then go on on their journey and pass right through the earth and exit on other side and head for the sun and pass straigth through it like nothing ever happened and go on on their journey.
That's how our notion of the newtonian world arises. It's based on what we are able to perceive through the body apparatus(somebody used the word "interface" earlier). A bat sees the newtonian world differently as it's not limited by the availability of light, as it uses echolocation.

So if i were to use a summary, i'd pick my initial quote:
We don't see the whole picture, that's how/why the newtonian world arises from space phase in our brains. It's our peculiar, limited and "coarse" sensory apparatus that brings about the notion of 3D vision.


there would be no Newtonian world if there were no living forms

Why?


Because it arises in the mind. If you didn't have the senses you have in your body, you wouldn't know where the atoms of an object end and where the atoms of air take over. At the very least, you need senses + a brain to infer the implied "meaning" in the phase space.

[Hurkyl]

The unitary evolution, by itself, does not explain our observations. We never observe superpositions.
What observations are unexplained? What does it mean to "observe a superposition" -- and how would observing a superposition look differently than if there wasn't a superposition?

(I'm not being glib here -- I mean this quite seriously)

[ueit]

What observations are unexplained? What does it mean to "observe a superposition" -- and how would observing a superposition look differently than if there wasn't a superposition?

(I'm not being glib here -- I mean this quite seriously)

By "observing a superposition" I mean observing the reality as it is supposed to be - a state vector in a Hilbert space, not point particles in a 3d space.

[vanesch]

You are making a claim about how a huge, complex system (the brain) works.


No, not at all. This is not about brains as you (think you) know them, because a brain is then also totally different (it is a projection of a point in N-dimensional space on an M-dimensional hyperplane), but there is a 1-1 relationship between this "single-point" brain in the M-dimensional hyperplane, and the "many points" brain in 3 D. Imagine for a moment that a true brain is a single point in the M-dimensional hyperplane. In order to function well, that is, to have evolutionary advantageous dynamics, it is such that patterns are recognized. It turns out that these patterns are most conveniently organized as "many points in 3D", because this then shows up most easily relationships that occur in interactions (the concept of 3D-distance and so on). So even a "single-point-in-M-dimensional-hyperplane" brain would probably give us sensations that correspond to a 3D space "out there".

Of course, I agree that the very fact that this 3D structure (including that 3D Euclidean distance thing) is so very well organizing (so well that our brains are wired up to interpret our sensory nerve pulses that way) is an argument in favor of saying that this might then be the best structure that corresponds to our sensations. But as I said, that's a matter of taste. If you are marveled by the simplectic structure of Hamiltonian phase space, then you might give this more importance over this 3D Euclidean distance thing.


Not only this is open to inconsistencies (may be your assumption contradicts energy conservation or some other physical constraint) but is a way to bring other assumptions throug the back door (a kind of cheating).


I don't think it would lead to inconsistencies, given that Hamiltonian dynamics is mathematically equivalent to Newtonian dynamics. Any inconsistency in the Hamiltonian dynamics picture would then translate in an equivalent inconsistency in Newtonian dynamics.


I've read for example some so-called deductions of Born postulate from decision theory. But all this assumes already that a reasonable brain exist and that such a brain functions according to Born postulate. Circullar reasoning in the end, but well hidden.

Yes, in fact you are pointing to Deutsch's work. In fact I agree with you, I even wrote a rebuttal paper on it, but I didn't get it published. Indeed, I demonstrate in my paper that Deutsch uses hidden assumptions which are logically equivalent to assuming the non-contextuality property, from which it was already demonstrated that it is equivalent to assuming Born's postulate (that's nothing else but Gleason's theorem). My comments were considered "correct but irrelevant" by the reviewers of the journals I submitted it to (Royal society and Foundations of Physics).

[vanesch]

The additional postulate you need is simply the definition of observer states. The fact that the fundamental Hamiltonian contains local interactions takes care of superpositions that are widely separated in position due to decoherence.

You cannot expect that a fundamental theory would tell you how to define an observer. The best you could do in theory is to use the thoery to compute what an observer, put in by hand but defined in the language of the theory, would evolve as he interacts with the rest of the universe.

:approve: This is indeed very important. Ultimately, one needs always a "theory of observation" (read, of subjective observation).

[Hurkyl]

By "observing a superposition" I mean observing the reality as it is supposed to be - a state vector in a Hilbert space, not point particles in a 3d space.
I thought reality was "supposed to be" a shadow play put on by 38-dimensional invisible pink unicorns. (Okay, this part is glib)

Ontological biases aside, you didn't really answer my question, you just restated it in an equally vague way, with equal problems. What does it mean to observe reality "as a state vector in a Hilbert space"? What about "as a point particle in a 3d space"? And how are they observationally different?

[mn4j]

People think objects are at rest when every particle they are made of is in constant motion at immense speeds.

Fallacy: The people are thinking about the object not the particles making up the object. The speed of the constituent particles does not necessarily determine the speed of the object.


People think objects are made of "stuff", when solid objects feel solid because of a force called electromagnetism. Switch off electromagnetism and the strong nuclear force and the otherwise "solid" looking objects will disappear. People think solid objects are solid and physical when even the biggest physical thing they have ever seen in their lives - the Sun will disappear into a zero dimensional "point" without a trace if it were to hit a black hole.

Fallacy: By definition, without the "stuff", there will be no force called electromagnetism. So if you think about it, "People" are right and you are wrong, objects are indeed made up of "stuff". If you disagree, define "stuff". I will also be entertaining to hear your definition of the words "solid", "physical", etc.


But that's an abstraction created by the mind and the inputs of our "coarse" sensory apparatuses at our level of existence.

This is intellectual suicide. How are you sure that your current analysis is not just an abstraction created by your limited mind. Ohoh! You can't because you have nothing better to rely on than "coarse sensory aparatuses".


People think the universe is lit when in reality it's fundamentally dark. We've "picked" one wavelength of the EMR spectrum and "learned" to use it to find our way in the dark, but fundamentally there is no light and the universe is dark. It's lit only to us, who have this peculiar human sensory apparatus(and to the animals that have vision).

Fallacy: You apparently have a different definition of the words "lit", "dark". Without language you can not communicate what you mean. How can you purport to say what the universe is without obeying the simplest conventions of communication such as obeying the meanings of words?


At the fundamental level, the universe is much different to what we think of it, due to the way we see it. Had we used neutrinos instead of photons for our vision, we'd see only extreme light and empty space.

It is one thing to characterize different levels of observation. It is another to completely disregard one level of observation just because if you look at a more detailed level, you see more. Of course if circles were squares, mathematics will be different. But circles are not squares by definition -- language again!


We don't see the whole picture, that's how/why the newtonian world arises from space phase in our brains. It's our peculiar, limited and "coarse" sensory apparatus that brings about the notion of 3D vision.
Because it arises in the mind. If you didn't have the senses you have in your body, you wouldn't know where the atoms of an object end and where the atoms of air take over. At the very least, you need senses + a brain to infer the implied "meaning" in the phase space.

Observation by definition requires an object which is being observed. To say that the object arises in the mind as a result of the observation is not even wrong. It makes no sense. It's an abuse of language and all logic. Just because you don't know where the atoms of an object end and where the atoms of air take over does not mean the atoms of the object do not end somewhere. So long as you are being kind to your language and maintaining a consistent definition of what it means for atoms to end.

[Hurkyl]

Is this even on topic anymore? If we want to discuss epistemology in a capacity not related to the topic of the thread, then we should do so in a new thread, preferably in the philosophy forum.

[WaveJumper]

Fallacy: The people are thinking about the object not the particles making up the object. The speed of the constituent particles does not necessarily determine the speed of the object.


Fallacy: By definition, without the "stuff", there will be no force called electromagnetism. So if you think about it, "People" are right and you are wrong, objects are indeed made up of "stuff". If you disagree, define "stuff". I will also be entertaining to hear your definition of the words "solid", "physical", etc.


This is intellectual suicide. How are you sure that your current analysis is not just an abstraction created by your limited mind. Ohoh! You can't because you have nothing better to rely on than "coarse sensory aparatuses".


Fallacy: You apparently have a different definition of the words "lit", "dark". Without language you can not communicate what you mean. How can you purport to say what the universe is without obeying the simplest conventions of communication such as obeying the meanings of words?


It is one thing to characterize different levels of observation. It is another to completely disregard one level of observation just because if you look at a more detailed level, you see more. Of course if circles were squares, mathematics will be different. But circles are not squares by definition -- language again!


Observation by definition requires an object which is being observed. To say that the object arises in the mind as a result of the observation is not even wrong. It makes no sense. It's an abuse of language and all logic. Just because you don't know where the atoms of an object end and where the atoms of air take over does not mean the atoms of the object do not end somewhere. So long as you are being kind to your language and maintaining a consistent definition of what it means for atoms to end.




I'll keep this as short as possible since we are offtopic, but everything you've said is a mis-representation of what i had said. I am not even sure you were replying to my posts, it seems you picked up a subject you wanted to talk about, and you thought it'd be somehow appropriate if you attributed it as a reply to my posts. And since you seem to be entertained about discussing "solid", physical matter, may i suggest you have a look here:

http://www.newscientist.com/article/dn16095-its-confirmed-matter-is-merely-vacuum-fluctuations.html

[ThomasT]

Is this even on topic anymore? If we want to discuss epistemology in a capacity not related to the topic of the thread, then we should do so in a new thread, preferably in the philosophy forum.
That sounds like a good idea as there are some things being said that I'd maybe like to address, but the philosophy forum would probably be a better place to do it.

In lieu of that, here's my two cents regarding the original poster's question:






Given the hypothesis that everything that exists came from an original singularity, would it not follow, in physics, that everything is "entangled"?

I don't know, maybe I'm way-off here, but somehow it seems plausible.
The only unambiguous definition for quantum entanglement is via quantum theory. There isn't a coherent, comprehensive classical conceptualization of what entanglement is wrt analogies of phenomena that can be described with ordinary language. That is, quantum entanglement is only physically defined and observed wrt quantum experimental phenomena.

But, for the sake of argument, lets suppose that we can have some idea of the deep qualitative nature of entanglement vis, say, conservation principles. Lets suppose that the evolution of the universe can be traced back to a single cataclysmic event that set things in motion. We won't call it the 'big bang' because that term refers only to a set of cosmological models regarding the evolution of the universe and not to some universe-originating event. We won't call the initial state of the universe a 'singularity' because that term refers only to the extrapolational limits of the mainstream theory that's the basis for the mainstream cosmological models. As far as anyone knows, the universe appears to be expanding and evolving (its state is continually changing) and its initial state (size, configuration, contents, etc.) is described vis various backward extrapolational techniques and will always be somewhat speculative in nature.

Having said that, and retaining our supposition that we have some idea of the deep qualitative nature of entanglement, we can infer that the original constituents of the universe were entangled wrt the originating cataclysmic event.

The problem with the idea that all of the current constituents of the universe might be entangled with each other is the fact that entanglement (whether stricly quantum or some classical conceptualization) is both produced and destroyed via interaction.

As ZapperZ stated, even one interaction can destroy the coherence of a single-particle quantum state. Since we're living in an epoch that is the product of billions of years of evolution entailing an incomprehensible number of interactions, it seems reasonable to assume that the original entanglements have been destroyed.

While there still might be an entanglement of sorts regarding the behavior of large scale cosmological structures wrt the isotropic expansion of the universe as a whole, you'd have a difficult time communicating it in any form other than as a metaphysical heuristic.

So, I'll join with others who have said that the answer to your question is, no, it's not plausible that everything is entangled.

[Hurkyl]

The problem with the idea that all of the current constituents of the universe might be entangled with each other is the fact that entanglement (whether stricly quantum or some classical conceptualization) is both produced and destroyed via interaction.
IMO that's inaccurate. Interactions almost always result in entanglement; the problem is that the entanglement spirals out of control. Only an interaction involving the entire entangled system can detect it, but it's still there. Only in the collapse model of quantum ontology does the entanglement get destroyed (due, of course, to collapses) -- in the decoherence model the entanglement simply spreads exponentially, quickly becoming too vast to be able to observe.


As ZapperZ stated, even one interaction can destroy the coherence of a single-particle quantum state.
But, as he did state, it results in a coherent two-particle quantum state. And another interaction would result in a coherent three-particle state, and so on.

ZapperZ: If you're still reading, this is, I think, the point where I have lost your train of thought. We have 'compelling evidence' of the coherent two-particle state, and of the three-particle state... the part I don't get is why you're so staunchly opposed to the "and so on" part.

[atyy]

ZapperZ: If you're still reading, this is, I think, the point where I have lost your train of thought. We have 'compelling evidence' of the coherent two-particle state, and of the three-particle state... the part I don't get is why you're so staunchly opposed to the "and so on" part.

On experimental procedures for entanglement verification
S.J. van Enk, N. Lutkenhaus, H.J. Kimble
http://arxiv.org/abs/quant-ph/0611219

I haven't understood the details of this paper, but anyway there are Alice and Bob as usual, plus:

Quinten who "believes in quantum mechanics but does not trust Alice and Bob";

Victor who "lets Alice and Bob teleport a state that he hands over", then checks that the output state is "close to his original input state to warrant the conclusion Alice and Bob must have made use of entanglement"; and

Rhiannon, who "just like Quinten, mistrusts Alice and Bob and performs her own measurements on states handed over to her by Alice and Bob. But unlike Quinten, she does not believe in quantum mechanics and tries to construct a local hidden-variable model that describes her measurement results."

So my question is for the universe, God is presumably Alice and Bob, and Quinten is ZapperZ? In which case, could it be possible that the universe is not an entangled state to start with, but if it is, could ZapperZ perform any ideal experiment to verify it?

[ThomasT]

IMO that's inaccurate. Interactions almost always result in entanglement; the problem is that the entanglement spirals out of control. Only an interaction involving the entire entangled system can detect it, but it's still there. Only in the collapse model of quantum ontology does the entanglement get destroyed (due, of course, to collapses) -- in the decoherence model the entanglement simply spreads exponentially, quickly becoming too vast to be able to observe.
Ok, but the decoherence model is still subject to thermodynamic laws and c. A particular entanglement is either lost via dispersion and dissipation or is, via substantial interaction, altered beyond possible detection, or destroyed completely. And the exponential spreading is limited by c. Some events are completely isolated from others, whether the universe is finite or not, given that our universe is expanding at c.

So, in what sense could it be said that the evolution of the universe is an entanglement? In what way might all the constituents of the universe be entangled with each other? How can we physically relate everything in the universe with everything else?


But, as he did state, it results in a coherent two-particle quantum state. And another interaction would result in a coherent three-particle state, and so on.
Good point, however none of the resulting ("and so on") states is entangled with the behavior of anything from which they are, not just for all practical purposes but in principle, isolated -- although there is still the possibility of talking about universal entanglement wrt the motion of the universe as a whole. Whether this can be done in any physically meaningful way is a matter of speculation.

[schroder]

:approve: This is indeed very important. Ultimately, one needs always a "theory of observation" (read, of subjective observation).

Not to belabor the (possibly) epistemological/philosophical argument about whether our perception of the Universe in 3-D is purely subjective and/or a product of how our brains are wired, but I think it is important to note that there is other compelling (mathematical) evidence for a Universe that has exactly three dimensions. Not the least of this is the inverse square law. This law applies not just to gravitation, but to all electromagnetic phenomena, including electric and magnetic fields. What other conclusion can we draw, other than that “space” or at least all objects in space, which adhere to the inverse square law, have extension in only three directions? Or is it possible for a body to have a field or radiate anything in a dimension in which it does not have a spatial extension?

[vanesch]

Not to belabor the (possibly) epistemological/philosophical argument about whether our perception of the Universe in 3-D is purely subjective and/or a product of how our brains are wired, but I think it is important to note that there is other compelling (mathematical) evidence for a Universe that has exactly three dimensions. Not the least of this is the inverse square law. This law applies not just to gravitation, but to all electromagnetic phenomena, including electric and magnetic fields.

Yes, you are right. There is clearly also some 3-D structure, simply because 3-D Euclidean distance is a very meaningful concept in many physical regularities (which w've written down as laws of nature). Now, whether that is some extra structure on top of a N-dim phase space, or whether that's all there is to it, is a matter of taste. The price you pay by considering *just* 3D space is that you loose the beauty of the symplictic structure (and the canonical transformations and so on) of phase space. The price you pay when only considering phase space is that you don't have a natural structure for Euclidean distance.

But you point out something very important: it are *formal* and *theoretical* reasons (next to philosophical ones) which may lead us to prefer this view over that one. Your argument was a formal one: if there's just phase space, how come we can express part of the dynamics in that phase space based upon an Euclidean distance in 3 D ? And that's indeed a good argument for 3D.

As I said before, this was just an analogy and maybe I went much too far in it: the original discussion was "is everything entangled" or is "nothing (or almost nothing) entangled".

And again, here we have a strong formal argument: if *everything* is entangled, we EXPECT observationally to observe NO quantum interference effects in all correlation functions that are of a lower order than including all degrees of freedom (of the universe). For all practical purposes, that means that "everything entangled" comes down to "no observable quantum interference". So that's perfectly in agreement with observation.
Of course, "no entanglement" also means "no observable quantum interference in correlation functions" - although they would allow so for quantum interference effects on single systems.

"Decoherence" can mean: irreversible entanglement with the environment, leading to "everything is entangled" and hence "quantum interference effects disappear" ;
or it could be just another word for "projection" or "quantum-classical transitition".

So both "everything entangled" and "nothing entangled" are views which are in agreement with the observation that we don't see quantum interference effects.

However, we have - as ZapperZ points out, with great difficulty - done experiments where the "decoherence is partial", or in other words, where a limited number of systems (2, or 3 or so) interact and "entangle". We then see, as expected, that individual systems don't show any quantum interference effects anymore, but that we DO have quantum interference effects in the correlation functions that correspond to the highest number of systems entangled (for 2, that is a 2-point function, for 3 it is a 3-point function).

[ueit]

No, not at all. This is not about brains as you (think you) know them, because a brain is then also totally different (it is a projection of a point in N-dimensional space on an M-dimensional hyperplane)

Sure, I've understood this.

there is a 1-1 relationship between this "single-point" brain in the M-dimensional hyperplane, and the "many points" brain in 3 D. Imagine for a moment that a true brain is a single point in the M-dimensional hyperplane. In order to function well, that is, to have evolutionary advantageous dynamics, it is such that patterns are recognized. It turns out that these patterns are most conveniently organized as "many points in 3D", because this then shows up most easily relationships that occur in interactions (the concept of 3D-distance and so on). So even a "single-point-in-M-dimensional-hyperplane" brain would probably give us sensations that correspond to a 3D space "out there".

I'm not saying that this is not possible in principle. However, all this talk cannot be considered a proof that 3d reality emerges from your proposed reality. May be it does, may be not. Therefore you still need to postulate all this in order to make your theory work.

Of course, I agree that the very fact that this 3D structure (including that 3D Euclidean distance thing) is so very well organizing (so well that our brains are wired up to interpret our sensory nerve pulses that way) is an argument in favor of saying that this might then be the best structure that corresponds to our sensations. But as I said, that's a matter of taste. If you are marveled by the simplectic structure of Hamiltonian phase space, then you might give this more importance over this 3D Euclidean distance thing.

Again, I disagree it's a matter of taste. A theory that takes our 3d-world as reality can ignore the observer completely. A theory that proposes a different reality must explain the observation act because this is the place where the 3D illusion (containing all the required experimental data) appears. So, such a theory is necessarily more complex, and this complexity should be balanced by an increase in explanatory power.

I don't think it would lead to inconsistencies, given that Hamiltonian dynamics is mathematically equivalent to Newtonian dynamics. Any inconsistency in the Hamiltonian dynamics picture would then translate in an equivalent inconsistency in Newtonian dynamics.

This is true if you take a Newtonian system that you know it's consistent and translate it into the Hamiltonian view. But this begs the question of what is the most fundamental description. If the Hamiltonian approach is the one, then you must work from the assumption of a brain being "a projection of a point in N-dimensional space on an M-dimensional hyperplane". You must show how you can recognize this point to be a brain, how it interacts with other objects and so on. If you choose a "wrong" point then this could lead to inconsistencies. In other words, forget completely about the 3d world, use only the new proposed reality and show in the end that 3d-world is emergent.

[ueit]

Ontological biases aside, you didn't really answer my question, you just restated it in an equally vague way, with equal problems. What does it mean to observe reality "as a state vector in a Hilbert space"? What about "as a point particle in a 3d space"? And how are they observationally different?

I see the world around me as a 3d space populated by objects that can be reduced at a collection of points. Or, to put it differently, I can imagine a computer simulation of our world based on points moving in a 3d space that is indistinguishable from reality.

On the other hand I have no idea what would mean an observation in your proposed reality (a universal wavefunction). I cannot see directly wavefunctions. You claim that I am a part of that reality, and when I make an observation (whatever that might mean in your description) I should "see" points moving in 3D space. Do you have a proof for that? Why exactly shouldn't I see 6D blobs waving in a 13D space for example?

[ManyNames]

Given the hypothesis that everything that exists came from an original singularity, would it not follow, in physics, that everything is "entangled"?

I don't know, maybe I'm way-off here, but somehow it seems plausible.

Maybe, if it did not arise from a singularity, because ordinary quantum rules do not hold from a singularity. If everything came from a single source which was a non-singularitarian solution, then perhaps we have matter and indeed, all matter and energy entangled in such way, we can two, four and eight particles at a time that are entangled.

So if we ever took up the time to observe a single electron, out of all the matter in the universe, which actually takes up less than 1% of all the spacetime in the universe, then maybe another electron located billions of light years away will have a spin-eignestate created for it. So yes, the theory is possible, as i have concluded.

[ThomasT]

And again, here we have a strong formal argument: if *everything* is entangled, we EXPECT observationally to observe NO quantum interference effects in all correlation functions that are of a lower order than including all degrees of freedom (of the universe). For all practical purposes, that means that "everything entangled" comes down to "no observable quantum interference". So that's perfectly in agreement with observation.
Of course, "no entanglement" also means "no observable quantum interference in correlation functions" - although they would allow so for quantum interference effects on single systems.

"Decoherence" can mean: irreversible entanglement with the environment, leading to "everything is entangled" and hence "quantum interference effects disappear" ;
or it could be just another word for "projection" or "quantum-classical transitition".

So both "everything entangled" and "nothing entangled" are views which are in agreement with the observation that we don't see quantum interference effects.

However, we have - as ZapperZ points out, with great difficulty - done experiments where the "decoherence is partial", or in other words, where a limited number of systems (2, or 3 or so) interact and "entangle". We then see, as expected, that individual systems don't show any quantum interference effects anymore, but that we DO have quantum interference effects in the correlation functions that correspond to the highest number of systems entangled (for 2, that is a 2-point function, for 3 it is a 3-point function).
You seem to be saying that we both do and don't observe quantum interference effects. So, which is it? Or am I just having a bad day? :smile:

My first thought about this is that we do see quantum interference effects, even up to macroscopic scales.

Anyway, what does seeing quantum interference effects (or not) have to do with whether it's possible that everything in the universe is entangled?

We know that some things are entangled.

But the only sense in which all things can possibly be entangled is wrt some holistic motion of the universe, eg. its rotation or its expansion.

Does that mean that it's plausible or possible that everything in the universe is entangled. Depending on what's meant by the terms, 'plausible' and 'possible', I guess it might, so I'll have to retract my original answer to pallidin.

Is there any physically meaningful way that such a 'possibility' could be formalized using qm?

I once asked a question about a 'universal clock' at sci.physics.research and got some very interesting replies. Maybe some of the creative qm experts here at PF can come up with something regarding everything in the universe being entangled wrt some property of the universe as a whole.

Could the degree of universal entanglement be related to the thermodynamic state of the universe?

Would it make any sense to say that everything's entangled wrt time asymmetry?