Is the cat alive, dead, both or unknown

[bhobba]

Do you imply that QFT is not realistic?

I make no claims one way or the other. Simply that locality in QM does not apply to correlated systems.

Thanks
Bill

 

[zonde]

The catch is obvious. Just what don't you get about QM can't be both local and reject naive realism?

Ok, rejecting locality leads to "action at a distance". So you say that the way out without involving "action at a distance" is to reject "naive realism", right?
Then what rejecting "naive realism" changes in that model I linked?

 

[bhobba]

Ok, rejecting locality leads to "action at a distance". So you say that the way out without involving "action at a distance" is to reject "naive realism", right? Then what rejecting "naive realism" changes in that model I linked?

See the conclusion: Reality must be non-local.

This is standard textbook stuff. All you have posted is an alternate derivation of Bells Theorem that showed you can't have both realism and locality. You can reject realism and retain locality - you can also reject both.

I am also saying that in QFT the concept of locality isn't even defined in this instance because it precludes correlated systems which EPR is. Its more subtle than the argument assumes.

Thanks
Bill

 

[zonde]

See the conclusion: Reality must be non-local.

This conclusion can't be made before loophole free Bell test has demonstrated violation of Bell inequality. So it's currently not justified.
But this is conclusion, not the model. So can you point out the catch in the model excluding conclusion?

This is standard textbook stuff. All you have posted is an alternate derivation of Bells Theorem that showed you can't have both realism and locality. You can reject realism and retain locality - you can also reject both.

Relaxing realism might be standard textbook stuff in philosophical literature but certainly not in science literature.

I am also saying that in QFT the concept of locality isn't even defined in this instance because it precludes correlated systems which EPR is. Its more subtle than the argument assumes.

You don't have to define locality in physics, you get it included with concept of distance.

 

[my2cts]

Yes - so?

Thanks
Bill

Read your own post.
Thanks

 

[bhobba]

This conclusion can't be made before loophole free Bell test has demonstrated violation of Bell inequality. So it's currently not justified.

Bells Theroem is a theorem in QM. If QM is true its true. The loophole if its not closed would disprove QM.

This is all standard textbook stuff - why you want to rehash it beats me.

Thanks
Bill

 

[bhobba]

Read your own post.

I know what I said. If you don't agree what pure state is system A in?

Thanks
Bill

 

[bhobba]

Relaxing realism might be standard textbook stuff in philosophical literature but certainly not in science literature.

You might like to read what Bell said:
https://cds.cern.ch/record/142461/files/198009299.pdf

Or even our own Dr Chinese.

Again this is standard textbook stuff eg Chapter 20 Ballentine.

EPR started it all with it's elements of reality:
http://www.drchinese.com/David/EPR.pdf

Can you please read the literature first.

Thanks
Bill

 

[my2cts]

QUOTE="bhobba, post: 5147364, member: 366323"]I know what I said. If you don't agree what pure state is system A in?

Thanks
Bill[/QUOTE]

A and B are entangled, so they are not acting like separate systems.
You ask the wrong question.

 

[bhobba]

A and B are entangled, so they are not acting like separate systems.

Exactly. And in that case what I proved in that an observation on system A shows its in a mixed state.

Thanks
Bill

 

[my2cts]

I know what I said. If you don't agree what pure state is system A in?

Thanks
Bill

I am glad you do. I also know what you said.
The cat subsystem is not in a superposition state, but the entire system is.
(Unless somebody is watching, who then becomes entangled with it).
In one of the states making up the complete state, the cat is alive. In the other it is dead.
Unless that whole/broken flask of HCN is overlooked, the observation is of the entire system.

 

[bhobba]

I am glad you do. I also know what you said.
I argue that the observation is not on a subsystem (the cat) but on the entire system.
Unless you overlooked that whole/broken flask of HCN, the observation is of the entire system.

Well I believe, and every textbook I have read on it says (its all standard textbook stuff) that if you observe system A you are not observing system A+B. It seems rather obvious. But if you don't agree - shrug.

Thanks
Bill

 

[zonde]

Can you please read the literature first.

Thanks for your concerns, but I have read the literature.

 

[my2cts]

Well I believe, and every textbook I have read on it says (its all standard textbook stuff) that if you observe system A you are not observing system A+B. It seems rather obvious. But if you don't agree - shrug.

Thanks
Bill

We probably read a disjoint set of textbooks. Mine said that if you observe A+B you do not observe A!
Try a different textbook.

 

[write4u]

I was referring to the Bohm's state of pure potential from which the Implicates form, which then are expressed in reality as the ExplicatePerhaps I am using this in the wrong context, but this link came to mind, https://en.wikipedia.org/wiki/Quantum_superposition

Bohm's implicate order is more philosophical musings (that's being charitable) than actual physics:
https://www.physicsforums.com/threads/david-bohms-holographic-paradigm-of-the-cosmos.252110/

As the above thread explains he had a number of phases - unfortunately that wholeness stuff was from the mystical, bonkas, meaningless phase. That in no way demeans the work of his excellent and brilliant phases.

I now understand what you are talking about however - the quantum potential is part of Bohmian Mechanics from his brilliant phase. However the implicate order stuff is, being kind, philosophical musings, but really its mystical nonsense.

Thanks
Bill

Thank you for clarifying. It's interesting that you understand and admire his physics but reject his metaphysical "musings". I have little knowledge of QM, but I identify with some of his metaphysical descriptions. I do agree that it probably has very little RW value. I just like the concept of the Pilot Wave and its inherent superposed potentials becoming expressed through a series of hierarchical steps.

I thought this might somehow apply to Schrodinger's Cat.

 

[my2cts]

if you don't agree - shrug

Not only I do not agree, it is worse.
You present a point of view that is at least incomplete if not incorrect.
But hey, shrug you too !

 

[bhobba]

Mine said that if you observe A+B you do not observe A! Try a different textbook.

It's called removing system B from control by a partial trace.

The bible on this is Schlosshauer - Decoherence - And The Quantum To Classical Transition. See section 2.4.6 on the reduced density matrix.

Of course it is entangled with system B - I am not denying that - in fact I specifically said it was. However if you just observe system A then its in a mixed state. There is no attempt to hoodwink anyone, tell an incomplete story etc etc. Its simply if you just observe system A you are not observing system A+B. In fact often, like Schroedingers cat, you don't even have access to system B.

Thanks
Bill

 

[Nick666]

I have read somewhere that Bell relies on counterfactual measurements , and these measurements somehow arent possible in nature ?

The math was something like: How can

be true at the same time as

, and still have a function that is time dependent ?

 

[bhobba]

I have read somewhere that Bell relies on counterfactual measurements

Counterfactual measurements are simply measurements you didn't take - its associated with counterfactual definiteness which a link has been given to.

Its one of the assumptions in Bell - most say it's the same as naive reality - but there is a subtle difference.

Thanks
Bill

 

[Nick666]

Allright, I see you say (?) that Bell's theorem (and QM) contradicts naive reality, but Bell(and QM) assumes CFD, so there must be some difference between CFD and naive reality, but what is that subtle difference ?

 

[rootone]

States which can only exist given that their opposite exists.
There has to be a movie in there somewhere.

 

[Nick666]

And what about the math thing I wrote ?

 

[zonde]

Allright, I see you say (?) that Bell's theorem (and QM) contradicts naive reality, but Bell(and QM) assumes CFD, so there must be some difference between CFD and naive reality, but what is that subtle difference ?

Maybe bhobba associates "naive realism" with non-contextual (hidden) variables. Say we believe that photon has objective property "polarization" and it can be determined by polarizer regardless of the state of polarizer (idependently from any hidden variables polarizer might have).
CFD I perceive as more general idea that it is meaningful to ask "what if" type questions. And these questions are meaningful even with contextual variables.

 

[atyy]

Allright, I see you say (?) that Bell's theorem (and QM) contradicts naive reality, but Bell(and QM) assumes CFD, so there must be some difference between CFD and naive reality, but what is that subtle difference ?

I don't quite understand this myself and am not sure what counterfactual definite really means nor if everyone means the same thing by it, but according to https://en.wikipedia.org/wiki/Interpretations_of_quantum_mechanics MWI is not counterfactual definite. I would certainly count MWI as "naive reality" (assuming it works). So that could be a case in which naive reality and CFD differ. I find it easier to say that one assumption of a Bell inequality is that each experiment has only one outcome, whereas MWI assumes otherwise.

 

[harrylin]

[..] Basically in QFT locality is that uncorrelated experiments that are sufficiently separated in space have unrelated results. Note the keyword - uncorrelated. Entangled systems are correlated.

Standard QM is non-local to begin with because its based on the Galilean transformations.

Also in classical physics, uncorrelated experiments that are sufficiently separated in space have unrelated results... and in any case, Galilean transformations have nothing to do with non-locality!

 

[bhobba]

Allright, I see you say (?) that Bell's theorem (and QM) contradicts naive reality, but Bell(and QM) assumes CFD, so there must be some difference between CFD and naive reality, but what is that subtle difference ?

Its not me saying it:
http://drchinese.com/David/Bell_Theorem_Easy_Math.htm

Dr Chinse spells out the two assumptions. Here the assumption that is being discussed is:
I call this assumption "Bell Reality". And... this assumption is the equivalent of assuming that the moon is there when no one looks.

This is also called naive realism. But the technical assumption is counter-factual definiteness. Its the ability to speak meaningfully of observations that haven't been done.
http://physics.stackexchange.com/qu...lism-in-locality-and-counterfactual-definiten

I personally think they are the same - but philosophy types draw a distinction and logically they are correct - but its a bit nit picky in my view.

Thanks
Bill

 

[bhobba]

II would certainly count MWI as "naive reality" (assuming it works).

So would I. It however is not counter-factual definite because you can't speak meaningfully about future measurements.

Thanks
Bill

 

[Nick666]

But if in the Bell experiment counterfactual measurements can't physically be done , why would the experiment get physical predictions or physical results?

Or at least that's what I understand, that counterfactual measurements can't physically be done.

 

[bhobba]

But if in the Bell experiment counterfactual measurements can't physically be done , why would the experiment get physical predictions or physical results?

Couterfactual definiteness doesn't say they can't be done.

Did you go through Dr Chinese's proof?

Thanks
Bill

 

[zonde]

I think that people tend to mix what is sufficient assumption for Bell inequalities and what is necessary assumption.
Sufficient assumption allows proving Bell inequalities but relaxing sufficient assumption does not necessarily invalidate Bell inequalities.
On the other hand relaxing necessary assumptions would necessarily invalidate Bell inequalities.

Say assumption that hidden variables are non-contextual is sufficient assumption of Bell inequalities but it is not necessary assumption because contextual hidden variables can't violate Bell inequlities either.

 

[bhobba]

Say assumption that hidden variables are non-contextual is sufficient assumption of Bell inequalities but it is not necessary assumption because contextual hidden variables can't violate Bell inequlities either.

Where exactly in Dr Chinese's proof is there non-contextuality?

Its got nothing to do with it and I have zero idea why you want to bring it up. Bringing up irrelevancies really makes things hard to discuss.

Thanks
Bill

 

[zonde]

Where exactly in Dr Chinese's proof is there non-contextuality?

Well acctually this sounds exactly as non-contextuality:
"we are simply saying that the answers to the 3 questions "What is the polarization of a photon at: 0, 120 and 240 degrees?" exist independently of actually seeing them."

But my remark actually was not meant exatly at your last post.

Its got nothing to do with it and I have zero idea why you want to bring it up. Bringing up irrelevancies really makes things hard to discuss.

This discussion goes around assumptions of Bell theorem. It seems relevant to distinguish which ones are sufficient to speak about Bell inequalities being satisfied and which ones are such that relaxing them is suficient to violate Bell inequalities.
For example, you said that relaxing "naive realism" is alternative to "action at a distance". This would be true if you could demonstrate that "naive realism" is necessary condition for Bell inequalities.

 

[bhobba]

Well acctually this sounds exactly as non-contextuality:

Before going any further, not with links, but in your own words, can you please describe what non-contextuality is?

Thanks
Bill

 

[bhobba]

This discussion goes around assumptions of Bell theorem. It seems relevant to distinguish which ones are sufficient to speak about Bell inequalities being satisfied.

It is well known what they are:
http://www.johnboccio.com/research/quantum/notes/paper.pdf

Let us define a “local” theory as a one where the outcomes of an experiment on a system are independent of the actions performed on a different system which has no causal connection with the first. For example, the temperature of this room is independent on whether I choose to wear purple socks today. Einstein’s relativity provides a stringent condition for causal connections: if two events are outside their respective light cones, there cannot be any causal connection among them.

Let us define a “counterfactual” theory as one whose experiments uncover properties that are pre-existing. In other words, in a counterfactual theory it is meaningful to assign a property to a system (e.g. the position of an electron) independently of whether the measurement of such property is carried out. Sometime this counterfactual definiteness property is also called “realism”, but it is best to avoid such philosophically laden term to avoid misconceptions

Bell’s theorem can be phrased as “quantum mechanics cannot be both local and counterfactual”. A logically equivalent way of stating it is “quantum mechanics is either non-local or non-counterfactual”.

Now you can keep locality if you give up realism, you can keep realism if you give up locality, or you can give up both.

Another issue is if locality is meaningful for correlated systems. The cluster decomposition principle that defines locality in QFT specifically precludes it. So another out is to say locality isn't meaningful for entangled systems.

Thanks
Bill

 

[zonde]

Before going any further, not with links, but in your own words, can you please describe what non-contextuality is?

In post #93 i described non-contextuality using example:

Maybe bhobba associates "naive realism" with non-contextual (hidden) variables. Say we believe that photon has objective property "polarization" and it can be determined by polarizer regardless of the state of polarizer (idependently from any hidden variables polarizer might have).