## Is Nature is Local or Nonlocal?

In quantum mechanics there are two strong points of view. On one hand the philosophers of physics insist that Bell showed us that nature is nonlocal: "What Bell Did", and on the other hand qubists and practitioners of high energy physics stress that nature is purely local and there is no "tickle at a distance". Now last time I called this debate sterile because both sides are right as they talk about different things. Also I have yet to meet supporters of a camp not agreeing with the mathematical points of the other camp, and so it is all purely a matter of perspective. Hidden behind this seeming disagreement are the epistemic and ontic points of view.

Let's try to disentangle the arguments and explain this local-nonlocal divide. Let's start with the case for nonlocality. This point of view starts with quantum correlations. In the words of Bell: "correlations cry out for explanations". Now only two kinds of explanations for correlations were ever found:

- common causes from the past
- an event causing the other one

and neither of them are valid explanations for quantum mechanics correlations. The first kind of explanation falls under local hidden variable approach and this was disproved by Bell, while the second kind is forbidden by the special theory of relativity because spatial separated experiments were performed where there was not enough time for the signal to propagate from Alice to Bob side. The absence of a third explanation is typically stated as

**nonlocality.**Mathematically this is expressed as**violation of Bell's locality condition**:
\(p(s, t | a, b) = p^1 (s|a) p^2 (t|b) \)

**equivalent with parameter and outcome independence**.

Now no qbist is denying that quantum mechanics violates parameter and outcome independence because this is a solid mathematical and experimental fact. But the local point of view starts with

**no-signaling,**or the inability of Alice to influence the outcomes for Bob**(and unsurprisingly no nonlocality supporter is denying this either). In the QBist point of view, each measurement is local and quantum mechanics is a tool which updates my personal degree of belief in order to make sense of what I observe. The Alice-Bob correlations can only be determined when the two sides come in contact and for this to happen travel at speeds lower than the speed of light is required.**
To better understand this debate I encourage you to watch this meeting moderated by Brian Greene.

At 1:22:00 Rudiger Schack makes a provocative statement: quantum correlations are like Bertlmann socks. I think this is just an extravagant way of saying that quantum correlations are just correlations and no explanations are needed in general. [I cannot take Schack's Bertlmann comment at face value as this would imply he disagrees with Bell's mathematical statements from his famous Bertlmann's socks paper and that would be wrong].

Now since both sides agree on the mathematics and on experiments, but disagree on interpretation maybe there is a middle ground. Abner Shimony introduced the expression: "

**passion at a distance**" but in the charged atmosphere of today in quantum foundations this is not a popular point of view.
Behind the local-nonlocal debate there is a fracture of interpretation: is quantum mechanics ontic or epistemic? Jean Bricmont expresses best the ontic point of view around 4: 35 in the interview below:

"you need a theory about the world whose fundamental concepts are not expressed, the meaning is not expressed in terms of measurment".

The opposing epistemic point of view was best expressed by late Asher Peres: "quantum mechanics while correct it is not universal, some things must remain unanalyzed".

For now the supporters of each camp do not agree at all with the opposite point of view and seems that nothing can change their minds as each position is perfectly self-consistent. But what is my position because

**I am neither in the epistemic nor in the ontic camp?**
First, Asher Peres position is wrong because his argument is pure handwaving inspired by Godel's incompletness theorem. In Godel's proof there is this key step of arithmetization of syntax without which the proof falls apart, and this is missing from Peres' musings.

**More important, quantum mechanics can be reconstructed from the assumption of its universality**.**I believe the epistemic point of view is essentially correct, but**This implies a__I disagree that the Bayesian point of view gives you the complete story__. In fact I predict that quantum collapse happens in nature by itself (similar with spontaneous symmetry breaking) and that there is a boundary between quantum and classical due to dynamically generated superselection rules.**testable extension**of the quantum formalism and I'll talk about this in future posts. The same approach which allowed me to reconstruct quantum mechanics from physical principles predicts a**of quantum formalism using Grothendieck group construction.**__unique extension__**Let experiments decide if I am right or wrong.**
I also think the basic demand expressed by Jean Bricmont is perfectly valid, but I disagree that the Bohmian interpretation is the way to go. The main fault of Bohmian's approach is distinguishing the complex number formalism of quantum mechanics and splitting the wavefunction into the real and imaginary parts. The quantum harmonic oscillator can be successfully solved in phase space or in the quaternionic formalisms and one obtains the same predictions. However the actual representations are very different in mathematical terms, and who says complex wavefunctions deserves ontic status and quaternionic wavefunctions do not?

Finally, is nature local or nonlocal? Local or nonlocal are bad words lacking a precise enough meaning.

**Nature is pure quantum mechanical, quantum mechanics is universal, locality-independent and no-signaling.**
Hi, you're just hiding behind tons of fog and ill-defined terms and the whole movement of "interpretations" but what you say is just demonstrably and plain wrong physics. Your wrongness isn't a matter of interpretations.

ReplyDeleteThe fact that one can't transmit any real information superluminally using entanglement is a *fact*. It follows from all viable theories we use,and all experiments that have been done are compatible with this claim, too. To claim otherwise means to be expected to construct a totally different theory of Nature, start from scratch, and make it compatible with billions of observations that have been made.

The fact that the entanglement may only arise due to the subsystems' being in contact in the past - just like Bertlmann's socks - is another fact. This is a totally well-defined sentence. Just create entangled states that don't obey this condition if you "disagree". This is not a matter of disagreement. It's a matter of basic knowledge of modern physics. You are ignorant about the basics of modern physics.

Similar comments apply to everything else you tendentiously distort and misinterpret. Is quantum mechanics ontic or epistemic? These are two a priori ill-defined philosophers' adjectives, like most of the junk the philosophers write into their papers. Once anyone tries to make these adjectives well-defined, it is spectacularly clear that by "ontic", one means a classical description in terms of the exact point on the phase space - beables, all these things are synonymous. By epistemic, one means a probabilistic distribution on a space of possibilities i.e. phase space. That's what these folks always mean.

Nature is clearly neither! Nature is neither ontic nor epistemic in this sense. The laws of Nature allow us to predict probabilities, like in the classical statistical description, but unlike the classical statistical description, the quantum pure state is a maximally complete description of a given physical system and there can't exist any "less undetermined" information about the system - it is true by the uncertainty principle.

So at stage 1, all your comments are ill-defined philosophical words. At stage 2, you propose several possible classes of theories to describe Nature and *all* of them are wrong. The correct description is something that you eliminate a priori. What you are doing is not science. It is a religious defense of naive dogmas.

Gee Lubos, maybe you should try to understand what I am saying before commenting.

ReplyDelete"Nature is clearly neither! Nature is neither ontic nor epistemic in this sense." Duh, I agree with this (and I am also in the minority view).

Compare your statement with this: "I am neither in the ontic nor in the epistemic camp" and "Local or nonlocal are bad words lacking a precise enough meaning."

Your only point of contention (if any) should be with this: "Nature is pure quantum mechanical, quantum mechanics is universal, locality-independent and no-signaling."

Do you disagree that there is only QM and no classical physics? I think not.

Do you disagree that QM is universal? This means that it applies equally well to the system and the observer. Asher Peres disagreed with this, but from this I derive QM in a rigorous mathematical way so I contend the statement is true.

Do you disagree that QM is locality-independent? this means that due to superposition sometimes factorization is impossible. If you disagree you have no clue about QM.

Do you disagree that QM is no-signaling? This means you cannot send signals faster then the speed of light. If you do you are insane.

Now there is a disagreement between us on your statement:

"The fact that the entanglement may only arise due to the subsystems' being in contact in the past - just like Bertlmann's socks - is another fact."

Clearly you have not understood the Bertlmann sock paper (read it, I have a link to in the text) and did not hear about entanglement swapping (https://en.wikipedia.org/wiki/Quantum_teleportation#Entanglement_swapping). You can get entanglement without having been in contact in the past. And that is a fact verified in the lab.

By the I did not distort anything, and when you say it you sound just like Joy Christian with his strawman arguments. This is typical when you run out of concrete things to complain.

One more thing: I made a big claim which you did not pick up on: I claim I can extend the QM formalism. This is huge as QM is very rigid and *all* attempts at this in the past failed. My claim is that superselection rules can be generated dynamically (by the way, using only unitary evolution) and this mechanism is provable unique. I am currently pondering various experimental proposals to test this.

Finally, a question: are you jealous on Chris Fuchs for promoting QBism?

"Local" and "nonlocal" are not bad words at all. They have a totally well-defined meaning within modern physics. Relativistic quantum field theories are local. You're completely incapable of figuring out or remembering these simple things - such as the fact that serious physicists always do say that QFTs are perfectly local. There is no ambiguity here. Are you illiterate? Or what's the reason why you repeat the nonsense that "nonlocal" is a bad word - but you still pretend that you agree with me.

DeleteI don't know who Asher Peres or Chris Fuchs is. They're surely not important in physics.

Very funny. Short term memory loss perhaps: http://motls.blogspot.com/2015/06/is-quantum-reality-personal.html?m=1 And Peres' intuition about QM was at the root of QBism.

DeleteThe way I see it, if someone fights for the correct interpretation and you wholeheartedly agree with it they deserve praises not a knife in the back, but that is just me-call me old fashioned.

But you gave me an idea:next time I'll explain this business of Bertlmann's socks.

Yes, I won't memorize every person who has appeared in any blog post of mine. I am sure that if I wrote about people doing this stuff, my point has always been that they are not *worth* remembering. I honestly don't remember these names. It's pure garbage. Quantum mechanics was discovered by folks like Heisenberg, Jordan, Born, Dirac, Pauli, Wigner... and if one includes contributions from people who remained confused about the final product, Schrödinger, de Broglie, and others.

DeleteThe physical beef necessary for doing *everything* in physics and understanding their relationships has been around for 90 years - now it's 2015 so the number is round.

I am sorry but I need to agree with Lubos with respect to this. You cannot simply add "quantum teleportation" and say there was no connection whatsoever in the past because quantum "teleportation" implies some sort of initial entanglement. All these terms using "tele" and "portation" are misnomers trying to mask or confuse people. The main idea is the same: there is quantum correlation but no transfer of information of any kind. Also, be careful what do you understand by "teleportation"... try not using wikipedia too often... Sorry, but your post is full of mistakes. I suggest some basic quantum mechanics books, like Messiah Albert :p

DeleteDear atreus, it s OK to disagree if you bring concrete arguments of why. Also it is one thing to argue with me or anyone, and another to argue with experimental results. Quantum teleportation was realized in a lab and is a real effect (although it does not have the naive meaning from Star Trek). In entanglement swapping the only thing which connects Alice's particle with Charlie's particle are classical bits of information and the two particles never interacted in the past in a direct way.

DeleteWell, it's really easy to see:

Deletehttp://phys.org/news/2007-10-entanglement-swapping-quantum.html

the "joint measurement" does the trick here. So, that's how you get here the "entanglement" and the "swap" you are talking about.

"In their scheme, two independent pairs of entangled photons, A1-A2 and B1-B2, are emitted by autonomous sources. By taking a joint measurement on one photon in each pair (A1 and B1), these photons fall into an entangled state (later verified using detectors), one of the four so-called “Bell states,” named for physicist John Bell, a key contributor to quantum physics. The joint measurement is thus known as a Bell-state measurement (BSM), and it is the foundation of the experiment.

As a result of the BSM, the two remaining photons (A2 and B2) are projected on an entangled state despite being unaware of the other's presence and never having previously interacted. Hence the entanglement of the initial pairs has been “swapped.”

"

I may disagree with Lubos on almost all climate problems but basic quantum mechanics he knows as good as I do... :p He definitely knows string theory not as good as I do, but that's another trick...

Atreus, yes I know Lubos knows QM, and I never claimed there is no connection whatsoever in entanglement swapping: there are 2 pairs of Bell state particles so in each pair the particles were in contact, and later on a representative of each pair comes in contact again. But the other 2 never interacted and still they became entangled.

DeleteLook, I am having problems explaining the simple business of Bell locality condition which should be completely uncontroversial and straightforward and I simply don't have the energy to argue advanced topics so I'll postpone this to another time.

In my next post I'll explain the socks paper diving in depth into what Bell said and did.

I knew perfectly well what you meant, and my reply was tongue-in-cheek. But seriously now, you missed the forest due to the trees. QBism is not universally accepted and Fuchs and Schack bear the brunt of abuse from the community for their support of this position. I don't think you have any clue how bad this abuse is. Heisenberg, Jordan, Born, Dirac, Pauli, Wigner, are all dead guys and someone has to carry the fight. Also QBists do not claim they discovered QM, the fight is all about its interpretation. Your assertion that QM's interpretation is long settled is bogus. There were subtle differences between the Copenhagen guys. I am sympathetic to QBism, but I have my own small variation (I am a neo-Copenhagen believing the wavefunction is just a tool to predict outcomes without any ontic value.). In fact I can trace my intuition about QM and mathematical approach all the way to Bohr: Bohr passed his intuition to his assistant Aage Petersen who later on worked with Emile Grgin at Yeshiva University to put Bohr's intuition on solid mathematical footing resulting to what now is called the Jordan-Lie algebra. Later on I got all this from Grgin and I continued his ideas resulting in QM reconstruction from physical principles:

ReplyDelete(1) QM is universal

(2) laws of nature are stable (not changing under time evolution)

This is all you need to recover the complete mathematical formalism of QM using category theory arguments. The collapse postulate however is mathematically inconsistent with the formalism but I know how to restore consistency (there is only one way to do it) and predict new physics in the process.

These strings of words go nowhere. Leaving out the apparatus from the theory is as bad as leaving it out in practice. In the first case you learn nothing because you only hear what you put in yourself, in the second case you learn nothing because no information is gained. The only point of contact between the quantum formalism and reality lies in measurements. One should thus analyze what happens in a realistic experiment. Fuchs and Sack said in a round table at the recent Vaxjo conference that they oppose that view. Hence they don't care about the physics which goes on. But then we can't call them physicist and we should not care about their words, words and words. If you're dreaming about the question how Nature gets entanglement done, better think of information traveling with the pair of particles, forget this nonlocality crap.

ReplyDeleteHi Theo, nice that you follow this. I was brain dead from jet lag during the round table and it is all a haze to me what was said there, but my prior recollection about QBism is that the measurement apparatus is part of their description. In fact Chris in his usual presentation has this creepy drawing of an one-eye person with measurement dials instead of hands.

ReplyDeleteI am not arguing for non-locality but the local-non-local debate is a dialogue of the deaf: no nonlocality supporter claims action at a distance, and no locality supporter claims factorizability.

Most amusing is Lubos' position. He is full of conviction and passion, which is good, but his knowledge of QM and its interpretations is really rusty. Yesterday he was in the consistent history camp, today he is in QBist camp, but I don't think he has any skin in the game. Calling yourself a Qbist and attacking Chris like the qbist interpretation already won the day and now is the time to fight for the credits do not go together.

"I am not arguing for non-locality but the local-non-local debate is a dialogue of the deaf: no nonlocality supporter claims action at a distance, and no locality supporter claims factorizability."

DeleteAre you saying that this dialogue of deaf is a matter of semantics only!!

How can one believe in locality (special relativity) and still call for non-local interactions? Do you think most non-local arguers believe in SR?

"How can one believe in locality (special relativity) and still call for non-local interactions?" I know no sane person calling for non-local interactions (unless you believe in voodoo ;) )

ReplyDeleteSee equations 8,9, and 10 in http://plato.stanford.edu/entries/bell-theorem/

Equation 10 is a factorization condition which is violated by nature. Its name is "Bell locality". I did not name it myself, I just report on the usual term from literature: this is its standard name for many years now. Since nature violates Bell's locality, nature is therefore called non-local by the supporters of this point of view. But this is not the same as action at a distance, signal at a distance, non-local interactions, voodoo, violation of SR, etc, etc. I am not sure how I can be more clear than this. Maybe I should say Nature is "non-Eq.10 from http://plato.stanford.edu/entries/bell-theorem/" instead of non-local :)

The way I see it, a disagreement MUST be about the same thing. For example some people believe Eq 10 is respected by nature (and oh boy-there are such people) and some people believe Eq 10 is not respected by nature. In such a case you put it to the test and arrive at a conclusion. But when people argue about different things then it is a sterile discussion because such a debate cannot be settled and devolves into a religious war when one side denies the other the right to exist because they believe in a different interpretation, "the wrong one" for which they deserve to burn forever in the fires of Hell.

Kashyap, one more thing. The most important idea expressed by Lubos is this:

Delete"The value of this "call for middle ground" is zero."

Now I grew up in a communist country just like Lubos, and communism is a totalitarian philosophy. It's main totalitarian dictum is:

"you're either with us, or against us"

and this was expressed many times by all dictators from Lenin to Mussolini.

Lubos' statement is the key to understand his position. He is not seeking truth or understanding, he is seeking the complete destruction of any other points of view different than his.

Some people found this amusing as he is sticking his tongue out to people with authority. In a world of uncertainty some people find reassurance in his unwavering confidence. Some people learn genuine things from him as his points of view are mostly safe bets.

But his position does not withstand close scrutiny and the warts are showing. Now I know what I know and I know what I don't know and freely admit it, I have no big ego or big fame to protect. If you keep reading what I am writing I can promise you will learn new things about QM.

It's pretty breathtaking that you think that a discussion on locality in quantum mechanics may be "reduced" to the teachings you were told by Ceausescu. What do these things have in common?

DeleteBut if Ceausescu's wisdom is the only one you may comprehend, be my guest. I will phrase it using this analogy, too. You are presenting points of view that represent two disagreeing wings of the Romanian Communist Party. One of them says to the other that you're either with us, or against us. And you want to be in the middle of those, a middle ground communist.

But it's true that a competent person may sharply answer to the question whether he's with you or against you. He's against you - he is with the evil capitalists in Copenhagen. You are thousands of miles from the truth, from understanding quantum mechanics, somewhere in an undeveloped country (where children were totally grateful to me when I threw them some old salami from the train, while going to Bulgaria) where you try to find a compromise between some flavors of the communist ideology.

But *no* version of the communist ideology - classical physics - is right.

Lubos, I am a seeker of truth, not an enforcer of dogma.

DeleteContinuing in the same analogy, communists have a sole fixed idea: any enemy is a "fascist". The Hungarian revolution in 56 was done by "fascists", the Prague spring was done by "fascists", the 89 revolution in Romania was branded by Ceausescu as "fascist", the later demonstrators against the neo-communists were branded "fascist", etc, etc.

Now you have a fixed idea too: classical physics. How many times do I have to say classical physics is wrong and nature is pure quantum mechanical? May be news to you that most (but not all) of the foundation people field believe this strongly.

I am not a psi-ontic guy since there are no "beables", I am not psi-epistemic in the sense of Spekkens with measurements revealing hidden information. Measurements create the outcome, do not reveal what was already there. I am in the Copenhagen camp where the wavefunction is just a tool. Complex wavefunctions, quaternionic wavefunctions, Wigner functions are simply distinct mathematical representations of QM. The natural formalism for QM turned up to be category theory. There is a lot of advanced beautiful math involved in QM and there are beautiful deep connections with non-commutative geometry, Hodge theory, gauge theory.

It is entirely unclear what framework of physics you find correct or defensible or logical etc.

DeleteIn physics, there only exist two frameworks, classical physics - that had been used almost everywhere up to 1925 - and quantum mechanics which emerged 90 years ago and whose universal postulates were discovered and clearly articulated by the Copenhagen school. Among lots of other questions, QM unambiguously says whether there is nonlocality needed to explain the EPR correlations and the answer is No.

There is no third way. Any third way is a purely verbal demagogic propaganda, fairy-tales by philosophers and would-be philosophers.

Lubos, let me clarify it for you. There is no action at a distance, you cannot beat special relativity. In this sense nature is local, no ifs, ands, and buts.

DeleteQM is NOT classical mechanics. Classical mechanics has a neat factorization which is not present in QM due to superposition. The Bell states are not factorizable between Alice and Bob and this is a trivial math statement. QM is using the tensor product while CM is using the Cartesian product. Moreover, hopes to derive QM from local hidden variables were crushed by Bell's theorem. Bell's theorem is not about QM, but about proving EPR wrong. At the heart of Bell's theorem is Bell's locality condition. This codifies EPR's fuzzy intuition. QM (and nature) violates Bell's locality condition. In this sense nature is *non local*.

You may say EPR was wrong (which would be correct), and hence Bell's locality condition is a bogus requirement stemming from Einstein's delusions. Hence calling nature nonlocal is insane. However, Bell's locality condition is standard terminology deeply entrenched. Do not shoot the messenger for using standard terminology. When people call nature non-local they mean nature violates Bell locality condition and they do not mean action at a distance. The local-nonlocal debate is a sterile debate of the deaf where each side do not listen to the arguments of the other side as they are both correct because they talk about different things.

Personally I do not like to call QM or nature nonlocal. I prefer the term locality independent. Here is why. If theory of nature (let us call it T) is universal it means this: if system A is described by T and system B is described by T, then the composed system must be described by T as well. This is an extremely powerful mathematical condition because from this I can systematically derive the formalism of both QM and classical mechanics. Only QM and CM are universal theories and nature can be in only one of them, not something else, not a combination of both. There are no PR boxes in nature because of this, there is no consistent QM-CM theory of nature. Imposing Bell's locality condition singles out CM. Violating Bell's locality condition singles out QM. Basically it all boils down to having superpositions or not. Superpositions violate Bell's locality condition.

But instead of making a personal vendetta against EPR and Bell, I turn it into a positive thing: violation of Bell's inequality is the direct experimental proof that nature is quantum and not classical (sure, there is a ton of irrefutable indirect proof-most of all 20th century physics). The same thing happens in relativity. From a general principle of relativity you can derive either the Galilean group or the Lorentz group. It is the invariance of the speed of light which singles out the Lorentz transformations and reject Newtonian's ideas of absolute space and time. Nature is either Newtonian, or respects SR, there is no "doubly special relativity", or other unicorn theories.

EPR was wrong, and Bell was half right. Bell's theorem is 100% valid, but Bell's beables idea was a half baked attempt to solve the measurement problem. Now it is mathematically possible to rigorously prove there are no such things as "beables" which generate observables. Observables are (mathematically) provable primitive notions and measurements do not reveal preexisting values. Kochen-Specker theorem is of prime importance in understanding QM.

The wavefuction is a description of nature, it is *not* nature. Instead of seeing red and giving in to emotional impulses when you hear about Bell and his locality condition, please try to see reason and understand what I am really saying.

Lubos, one more thing. My interpretation of QM from above does not come from whimsical personal desire, but it is forced as a mathematical consequence from my approach to reconstruct QM. I am simply following the math and the interpretation cannot be any other way. When I reject beables it is not because I don't like them, but because I can prove they cannot exist. I am just starting to come out with my results and in the end the young research area of QM reconstruction will settle for good all the interpretation matters. Central to it is the solution to the measurement problem and I am actively working on it using insights from category theory. Just following the math. So far it did not lead me wrong.

DeleteOne more confusion I want to clarify. The bulk of people working in foundations are either in the ontic camp or in the epistemic camp in the sense of Spekkens. The Copenhagen camp is a small minority, and I include here QBism. The people working in QM reconstruction are also a small group.

DeleteI have my minute split with QBism but this is tiny compared with the differences I have with Bohmian, MWI, etc. Naturally when I want to promote my intuition about QM I greatly magnify the differences.

Now in the physics community at large, Copenhagen is prevalent and the foundation people are the minority. However this is more "shut up and calculate" than really understanding the finer points of interpretations. Something along the lines: "Bohr already figured it all out" or "if I only have a free afternoon I'll solve the interpretation problem". But the people working in foundations are not idiots. They understand QM extremely well and they follow their own motivations however strange and misguided they might seem or even be. And they are making progress. Time symmetric QM led to advances in metrology, information approaches led to quantum protocols, etc, etc. Now I don't think anyone takes the signals from the future seriously but weak measurements are here to stay.

You don't have - and your "colleagues" don't have - any alternative. By these talkative comments and associated "papers", you are just wasting the space on the servers' hard disks and people's time.

DeleteLubos, in science there is this little rule called "peer review". I have to explain my arguments to the satisfaction of what you derogatory call "colleagues". Thank God you are not one of them because it is impossible to please you even when you agree with the scientific content.

DeleteHi Florin!

ReplyDeleteI have been reading your debate with Lubos with lot of interest. At this point, I largely agree with Lubos i.e in local (SR) and non-real interpretation. If I examine my own mind(!) it could also be due to the fact that the non-real part agrees with my religion and metaphysics (Hindu) !! Funny isn't it? The whole confusion may have arisen because of your word "non-locality" which may very well be Bell's word for non-factorizability. As you know, for people who believe in SR, this rings a big fire alarm! But seriously, I do not believe in "shut up and calculate" philosophy. For one thing at my age (78) I cannot calculate much anyway! (Incidentally, I got my Ph. D. from Maryland in ancient times, 1964!). Unlike Lubos, I am interested in following interpretation debates. So I will read your blog and perhaps raise some questions. I believe, all these debates can be civil and polite.

I am still trying to understand your remark about entanglement swapping not involving contacts. My mathematics is not strong enough to prove how the *contactness" spreads. As you agreed, there are contacts involved at three places, generation of EPR pair, at both the places A and B, although not between A and B directly.

I cannot comment on eastern European upbringing.Fortunately, I grew up in India which is democracy and came to U.S. which is also democracy. So such things are not parts of my life experiences.

Hi Kashyap,

DeleteI am glad you follow this, and for my part I will keep it civil. Lubos' insults do not bother me in the least because I don't have a big ego and there is nothing to hurt there. In fact I find them mildly amusing, nothing more than simple temper tantrums.

But I do care to the extreme if I am right or wrong because after the dust settles this is all that matters and I will not let incorrect statements unchallenged. I will nail to the wall in a systematic and methodical way each and every wrong statements made by Lubos starting with this socks paper business. And I will do it with complete arguments explained the best I can. In the end let the correct arguments win. Show me that I am wrong and I will gladly admit it.

About entanglement swapping I recommend you to read the following two papers in this order:

http://arxiv.org/pdf/0908.1787.pdf

http://arxiv.org/pdf/quant-ph/0402014v2.pdf

I am a fan of this pictorial approach as I am working in the same category theory paradigm. In the future I will explain this at my blog, it is really interesting. It is all about the information flow. The flow is always continuous and at times seems to go from future to the past, but this is an alternative completely equivalent description to computing the final answer using the standard formalism. The fact that the flow is never cut corresponds to the idea that there must have been a direct physical contact where the flow line is drawn.

I agree with Lubos that entanglement just does not happen by magic out of thin air (that is why the flow lines are not disjoint) but I disagree with his narrow statement that you always have to have direct physical contact to get entanglement. Indirect connection are perfectly acceptable and entanglement swapping is a direct counterexample to his incorrect assertion.

About "nonlocality", this is a standard term with precise meaning. When in Rome, do as the Romans do. I would like to call it something else, but if I do I cannot get my papers published. If I will become famous perhaps I would have a shot to name it what I like, which is "locality independence".

The reason it is called nonlocality has to do with history. People working in the foundations used to have a very hard time given by people like Lubos. As the community grew and acquired clout, consciously or unconsciously they wanted to rub it in the face of the people who use to oppose them. It was a triumph of the winner, a spoil of the won war. Lubos on the other hand has no direct contact with the foundation community because nobody wants to deal with his insults; it takes a special kind of personality to be able to ignore it. His ideas are from the era when the foundation community was just emerging, and sometimes he looks like those Japanese soldiers emerging from the jungle 20 years after WWII ended: fighting battles of the yesteryear when in fact the foundation community moved on.

Florin,

ReplyDeleteI am resending this because I think it must have failed to go through. I went to Lubos' website last last week, which I do every few weeks or so, and saw that you are a target on a page he wrote. I feel in a way that both of you are in a way talking past each other. In fact in some ways both of you seem to be almost saying the same thing. The main difference is that Lubos spices up his words with sulfurous insults.

If you are interested I have done some calculations that illustrate how QM is not epistemic nor ontic. I could send them to you, and if I am wrong on something I presume you will not be as vituperous as Lubos.

Lubos is right in saying that entanglements are not established nonlocally. To get an entanglement of states one must have those states emerge from some local interaction, or the decay of some particle/state by a local interaction. This may not be quite the same with quantum gravity, where the diffeomorphism of spacetime is the quantum field, which could mean that quantum gravity is nonlocal in a deeper sense than standard QM. Lubos talks about wormholes on his blog in connection to the ER/EPR correspondence, which at this point is more of a conjecture. The problem is that if wormholes are equivalent to entanglement, then since general relativity does not involve topological changes we have absolutely no idea how the formation of a wormhole conforms to local or nonlocal physics. The fact the diffeos of spacetime are the field quantized it could mean this is far stranger than current physics.

An entanglement is only nonlocal in sense that entangled states are a single entity independent of space or time. There is nothing involved of course with communicating information. I get the sense that you and Lubos agree on this. In some ways the difference in this argument seem to amount mostly to the tone of language, where from Lubos it is largely angry.

I am not certain about how Lubos got discharged from Harvard, but largely I think it did amount to the fact that nobody could stand being around him.

Cheers LC

Hi Lawrence,

ReplyDeleteEntanglement does not appear out of thin air and you need local interactions in one form or another. However Lubos was not aware of entanglement swapping and the full picture is not as naive as he presents it. I think you put it best: "entangled states are a single entity independent of space or time".

I don't mind my exchange with Lubos: he is speaking his mind freely saying out loud what many people think privately, and I return the favor by letting him know what I think of him which is also what many people want to tell him but don't dare. I know not to argue string theory with him and in time he will learn not to argue quantum mechanics with me because he is not as good as he thinks he is.

Hi Lawrence,

ReplyDeleteI forgot to say, do send me what you have and I'll study it carefully. And I am not Lubos :)

Cheers,

Florin

My post went down or something.

ReplyDeleteEntanglement swapping is the key to teleportation of states.

I try to follow work on quantum foundations somewhat. I think quantum gravity hinges upon some of that.

I regard Lubos's judgment on particle physics as pretty first rate. I question some other things he says. He stated three years ago when the firewall problem was found that this was hogwash. The firewall issue is a serious obstruction to our understanding. He got rather quiet about that after a while. He is also adamant about global warming being a quasi-scientific hysteria. He is mainly concerned with defending an economic ideology, and in doing so is willing to misrepresent the science. He has misrepresented data on climate change, which is basically lying and a major flaw in a scientist.

I don't know that much about climatology. I did read Hanson's original paper and it more or less makes sense. It is a fairly straightforward analysis using the Stephan-boltzmann equation. Subsequent climate warming has in fact largely been what he predicted. At any rate if my doctor tells me that I have a form of cancer that needs chemotherapy and the rest I am not in much of a position to argue with him. The same goes with climatology, but Lubos seems to think he knows it all.

So how should I transmit my write up on what I have done? Mind you, I am a bit out of my league on this, but I think what I have done makes sense.

Cheers LC

Lawrence,

DeleteJust email it to me: fmoldove@gmail.com

I don't fully understand the firewall idea (I know what it is but I don't yet have a full intuition on it and I didn't worked out all the consequences) so I withhold comments on it.

On the global warming, denying it amounts to criminal irresponsibility IMHO. If you are wrong about QM or physics, who cares? Many people still read the zodiac columns in newspapers. But if you destroy the planet then it is game over. Nothing lives on a planet like Venus.

On QM first I thought Lubos was just rusty and I planned to rebut point for point his nonsense. However, in his last comment on the next post he had a breathtaking display of ignorance and that changed the game: it makes no sense to reply to finer points of disagreements when he lacks basic knowledge. His statement is equivalent with this one: "there are no Hilbert spaces in QM" and on the next post I will show how his statement is the same with denying Hilbert spaces.