Against Realism

Neil said:
By the way, I think Zeilinger holds a view similar to mine in the sense of emergent manifestations of physical objects from a non-local information background (field). Zeilinger is big on the quantum teleportation of quantum information, and it is difficult to interpret this along with all other experimental data in any realistic objective way.

People that attempt to maintain realism end up unable to fit all experiments, and end up trying to come up with all sorts of contortions like backwards causation, faster than light signaling, etc. but even with these contortions, realistic models fail at some point. Common is the inability to account for quantum teleportation, delayed choice, and virtual particles from quantum electrodynamics. I find it incredible that many theorists are MWI supporters yet MWI fails on many of these accounts. Objective collapse models such as GRW and Penrose objective reduction seem untenable due to the size of entangled and superposed molecules now experimentally demonstrated.

Essentially, physicists have tried and failed for the last 80 years to come up with an objective realist interpretation that works. It is still the subjective Copenhagen and von Neumann interpretations that work.

Many current physicists act like Heisenberg, Pauli, Schrödinger, etc were naive and just didn't know what they were talking about, but with the failure of objective interpretations, it seems to me that they may have had a pretty good idea of what was going on.
Click to expand...

I was reading up a bit on the von neumann role of the observer and I saw a few references to the fact that VM did not believe the observer had to be conscious, though other people who drew from his approach did. Is that your understanding?
 
I studied mechanical engineering before moving on to medicine... They used to beat us to death with physics. The Bell's/EPR dichotomy was part of it.
 
von Neumann did not support or oppose it either, he simply stated that it could take place at any step along the way (i.e. It could be the measuring device or the subjective perception of an observer). What you are thinking about is the von Neumann–Wigner interpretation, and he was dead by the time that Wigner postulated it. Relevant to this topic is that Wigner disregarded any form of realism.
 
E.Flowers said:
von Neumann did not support or oppose it either, he simply stated that it could take place at any step along the way (i.e. It could be the measuring device or the subjective perception of an observer). What you are thinking about is the von Neumann–Wigner interpretation, and he was dead by the time that Wigner postulated it. Relevant to this topic is that Wigner disregarded any form of realism.
Click to expand...

Hmm, this was not my account of von Neumann, in that I didn't think he said it could be the measuring device. After all, von Neumann chains are the potentially infinite chain of physical measurement/interaction that was supposed to require conscious observation to realize an outcome. Do you have anything I could read regarding this?
 
Neil said:
Hmm, this was not my account of von Neumann, in that I didn't think he said it could be the measuring device. After all, von Neumann chains are the potentially infinite chain of physical measurement/interaction that was supposed to require conscious observation to realize an outcome. Do you have anything I could read regarding this?
Click to expand...

I should have worded that better... The measuring device is part of the VN chain, what I meant is that you can arbitrarily "cut" the chain and collapse could be inserted in any step along the way without affecting the final result, including the measurement by the device (see Herbert's Quantum Reality, pages 147-48). Experience emerges at the site of collapse, mind is certainly involved, what is in question is at which step does it occur; is conciousness (as in awareness) the site or is it just identifying it? Arouet's premise is that he "did not believe the observer had to be conscious", and I replied by stating that he did not appear to favor or disfavor that statement. In other words, he was, at least IMO, closer to London and Bauer's randomness than Wigner's specific approach.

Edit: + pages
 
Last edited:
With that said, according to VN a measurement device with no observer would be condemned to perpetual superposition, so you can't get rid of the symbiosis.
 
Arouet said:
What I'm not getting is that I thought that when you entangle particles they basically become synced - so that in measuring one you know the measurement of the other. So I must be missing some key thing here.
Click to expand...
I think it is very easy to miss the point of entanglement. For example, if you placed a pair of shoes into two boxes (without looking) and mailed them to different places, then 'measuring' one box (i.e. opening it) would instantly tell you what was in the other one! Clearly physicists aren't discussing something analogous to that process :)

The actual process is a bit more complicated, and inevitably does not reduce to a simple analogy with the physical world.

Take a pair of entangled electrons with opposite spins. You send the electrons to two places, A and B where their spins are measured. Now the absolutely crucial difference from the shoe analogy, is that you can perform the spin measurement about any one of 3 possible axes (X,Y, or Z), and the result of the measurement will always be +1/2 or -1/2 (in suitable units).

If you think about it, it already doesn't make conventional sense because it is saying that whatever axis you use for the measurement, you will get one of those two answers.

OK, let's suppose that A measures his electron about the X axis, and gets the answer 1/2. This means that barring experimental error, if B also measures the spin about the X axis, he will get the answer -1/2 (analogous to the shoes). However, if he uses one of the other axes, he will get 1/2 or -1/2 with equal probability!

B can't tell from these measurements which axis A used for the measurement because all he ever gets is +1/2 or -1/2 regardless of which axis he chooses. However, if A and B compare their results after the experimental run (involving lots of entangled pairs) something magical results. Whenever A and B make their measurements about the same axis, one will be +1/2 and the other will be -1/2.

At first sight you might think this result might be analogous to a variant of the shoe 'experiment' in which you split 3 pairs of shoes and posted (say) (L,R,R) to A and (R,L,L) to B, but it isn't. One way to see this, is to think about what axes really are - they are 3 arbitrary mutually perpendicular directions in space - and this experiment works regardless of what overall orientation of the axes is used by A and B (but they should agree of course).

BTW, you get the same result whether A performs his experiment before B, or B before A!

I think this peculiar experiment encapsulates why QM is not compatible with realism, and remember, we are all made up of particles that behave just as described above!

David
 
Arouet said:
What I'm not getting is that I thought that when you entangle particles they basically become synced - so that in measuring one you know the measurement of the other. So I must be missing some key thing here.
Click to expand...

Both particles were just associated with each other in the past. There is no superluminal communication.

Roughly speaking, quantum systems can store information in a totally non classical/non realist way. That information is locally inaccessible, and only gets released when it interacts with other systems. The random system isn't really random.
 
E.Flowers said:
Max, superluminal communication is used as a device by the authors of the paper, they quote the ns as a control of sorts (it's the time that it would take for light to travel between buildings). If we try to stick to classical thinking, the only way that it would become obvious earlier that 100ns would be via FTL communication between both particles (they are not asserting that it is actually happening, but rather that the options are limited). I think that people seem to be missing that they are trying to falsify the concept, thus QM are not the main premise.
Click to expand...

I wasn't commenting on the paper.
 
Max_B said:
Both particles were just associated with each other in the past. There is no superluminal communication.

Roughly speaking, quantum systems can store information in a totally non classical/non realist way. That information is locally inaccessible, and only gets released when it interacts with other systems. The random system isn't really random.
Click to expand...

Thanks Max and David. You've given me some jumping off points, I appreciate it!

Of course, these jumps seem like they are down the rabbit hole!

To follow up on Max's point I googled "quantum system store information" and the first hit was a paper from Oxford which seems to say the opposite!
http://arxiv.org/ftp/quant-ph/papers/9906/9906007.pdf
 
Arouet said:
Thanks Max and David. You've given me some jumping off points, I appreciate it!

Of course, these jumps seem like they are down the rabbit hole!

To follow up on Max's point I googled "quantum system store information" and the first hit was a paper from Oxford which seems to say the opposite!
http://arxiv.org/ftp/quant-ph/papers/9906/9906007.pdf
Click to expand...

If that's the case your not understanding something correctly... the abstract is saying pretty much the same thing as I did.., that information is only released locally.
 
Max_B said:
Both particles were just associated with each other in the past. There is no superluminal communication..
Click to expand...

Well that isn't quite true - which is why Einstein talked about spooky action at a distance.

No useful information is passed across an entangled link, but the choice of measurement axis by A (in my above post) obviously affects what goes on at B.

David
 
Max_B said:
Both particles were just associated with each other in the past. There is no superluminal communication.

Roughly speaking, quantum systems can store information in a totally non classical/non realist way. That information is locally inaccessible, and only gets released when it interacts with other systems. The random system isn't really random.
Click to expand...

You mean the correlations aren't random?
 
Max_B said:
If that's the case your not understanding something correctly... the abstract is saying pretty much the same thing as I did.., that information is only released locally.
Click to expand...

As I read it the paper is aimed at what it identifies as a misconception about the non-local nature of both information storage that you mentioned (it holds that the information is not always locally accessible - but I don't think that's exactly what you were saying) and non-local information transfer (it goes through the calculations to demonstrate that all the information transfer going on in actually local, and not instantaenous as some believe). I think it addresses some of what David brought up as well. Here's a snippet:

Once again, we see exactly how the information about the angle q reached B: not through ‘nonlocal influences’ allowing it to ‘fly across the entanglement’ (Jozsa (1998)); not by residing in N as a whole rather than in any particular qubit David Deutsch and Patrick Hayden Information Flow in Entangled Quantum Systems 17 (Braunstein (1996)); not by travelling backwards in time to t = 1 with Q4 and then forwards again with Q5 (Penrose (1998)); not instantaneously (a traditional misconception that has sometimes found its way into textbooks – e.g. Williams and Clearwater (1998, §8.10)), nor through action at a distance (Williams and Clearwater (1998, §9.2)); nor of course through the ‘collapse of the state vector’ (since the state vector is strictly constant) – but simply, prosaically, in the qubits Q2 and Q3 as they travelled from A to B.
Click to expand...

I can't speak to its accuracy of course, but they do show detailed calculations for each step. I'll try and see if the paper got any traction.
 
Looks like it got a good amount of attention, having been cited 120 times, is that considered a lot for a 15 year old paper?) I imagine there's some spirited debate in there, given that it doesn't seem to have taken over as the dominant view.
 
Arouet said:
As I read it the paper is aimed at what it identifies as a misconception about the non-local nature of both information storage that you mentioned (it holds that the information is not always locally accessible - but I don't think that's exactly what you were saying) and non-local information transfer (it goes through the calculations to demonstrate that all the information transfer going on in actually local, and not instantaenous as some believe). I think it addresses some of what David brought up as well. Here's a snippet:



I can't speak to its accuracy of course, but they do show detailed calculations for each step. I'll try and see if the paper got any traction.
Click to expand...

That sounds like it's describing the many worlds interpretation that Deutsch supports based on the part about no state vector collapse and a "strictly constant" state vector. The MWI is full of all kinds of problems, so I no longer take it seriously.
 
You must log in or register to reply here.
Back
Top