B One single solution for paradoxes

[entropy1]

Is there one single interpretation possible without the paradoxes of QM, created by among others superposition, the measurement problem and non-locality?

 

[Simon Bridge]

Nobody knows.

 

[Vanadium 50]

There are no paradoxes. There are things you might not like, but that doesn't make them paradoxes.

 

[rubi]

I think the word "paradox" is used more broadly. For example the twin paradox in relativity is also not problematic, but it is still called a paradox.

A nice interpretation that is both local and has no measurement problem is the consistent histories approach. It is essentially the Copenhagen interpretation applied to histories rather than single events. It's roughly analog to the situation in stochastic processes (like Brownian motion) in classical probability. You can either formulate it in terms of probability distributions for events like detecting a particle that undergoes a Brownian motion at a certain time and a certain position or you can have a probability distribution over the set of paths of the Brownian motion. If you elevate these two points of view to the quantum picture, you get Copenhagen on the one side and consistent histories on the other. The nice thing is that the histories point of view clarifies a lot of things that are less clear in the Copenhagen picture and it kind of natural, since it just elevates techniques from classical probability to quantum theory. Here's a list of some of the paradoxes that are resolved by this approach:
http://plato.stanford.edu/entries/qm-consistent-histories/#ParRes

 

[eltodesukane]

Is there one single interpretation possible without the paradoxes of QM, created by among others superposition, the measurement problem and non-locality?

I don't understand what people mean by "interpretation".
What is an interpretation?
What is the interpretation of Classical Mechanics?
Why does Quantum Mechanics needs an interpretation?
Does Classical Mechanics needs an interpretation?

 

[entropy1]

I don't understand what people mean by "interpretation".
Interpretation of Quantum Mechanics?
To start, what is the interpretation of Classical Mechanics?

Yes, I mean the interpretation of QM.

 

[vanhees71]

An interpretation means many things, and it's very confusing particularly when it comes to quantum theory. The best way to learn QT is to read a physics textbook, which avoids "interpretation" for a long time and only has a chapter quite late in the book. The book without this chapter is probably the physics essence of quantum theory, i.e., what's really used by working theoretical and experimental physicists to understand real-world observations and experiments. A good example is the textbook by Gottfried:

K. Gottfried, T.-M. Yan, Quantum Mechanics: Fundamentals, 2nd edition, Springer (2003)

Interpretation can mean very different things. From a purely physical standpoint the only "interpretation" needed is to define how the abstract formalism of the theory is applied to describe real-world observations/experiments. In QT that's the "minimal statistical interpretation".

In QT you also have a lot of "interpretations" in the sense of philosophy, and this makes it a mess. Philosophy has the tendency to make such mess, because it addresses questions that are not so easily well defined in the sense to have a clear meaning. Some such question is, e.g., "what is the "meaning" of probabilities" or "is the theory realistic" and so on.

 

[entropy1]

...because it addresses questions that are not so easily well defined in the sense to have a clear meaning.

I guess I mean by the 'interpretation' that I seek, a description of QM that I can fully visualize. Might that be possible, realizable you think?

It seems to be the paradoxes that make it impossible to construct a coherent visual picture (that is probably why they are paradoxes ). So what I probably mean is: is it in principle impossible to reconsile the paradoxes?

That is also why I don't like "Do the math"; that suggests not to visualize at all. I can't do math without visualizing! So in that case, paradoxes break the visualization! And precisely that is what I mean: will there ever or in principle be a complete visualization possible of the formalism?

 

[vanhees71]

I don't know, what you mean. There are no paradoxes in QT.

 

[entropy1]

I don't know, what you mean. There are no paradoxes in QT.

For instance: the arbitrarity of the moment of collapse. The superposition of Schrödinger's cat. The non-local correlation of entangled particles. Why don't you call those paradoxes?

 

[A. Neumaier]

Why don't you call those paradoxes?

Because (according to https://en.wikipedia.org/wiki/Paradox)

• A paradox is a statement that, despite apparently sound reasoning from true premises, leads to a self-contradictory or a logically unacceptable conclusion.

and none of the phenomena you mention has this feature. Only an untrained sense of intuition is violated.

 

[Demystifier]

Why don't you call those paradoxes?

Define "paradox"!

 

[entropy1]

What I mean by paradox is 'an apparent contradiction'. So, not really a contraction, but it appears (presents itself) as such. This, of course, applies to interpretations of the math, not the math itself. However, a set of axioms can be conflicting while it is not imediately seen I think.

Furthermore I think that QM is consistent because of the concept of 'a state'. I would then classify the 'state' as being ontologically real.

 

[ZapperZ]

What I mean by paradox is 'an apparent contradiction'. So, not really a contraction, but it appears (presents itself) as such. This, of course, applies to interpretations of the math, not the math itself. However, a set of axioms can be conflicting while it is not imediately seen I think.

Furthermore I think that QM is consistent because of the concept of 'a state'. I would then classify the 'state' as being ontologically real.

Do you realize how silly this whole thing is?

It took you until Post #13 to actually DEFINE what YOU mean by "paradox". Until then, you were asking US to explain to you about these paradoxes based on YOUR definition of it, without bothering to tell us of it. So while the rest of us were adopting the standard definition of a "paradox", you were lost in your own world and expecting us to conform to what you mean. Maybe you forgot that this is not a "Psychic Forum".

Secondly, "an apparent contradiction" to WHOM? Show me something that you think has this apparent contradiction. If this is not an apparent contradiction to another person, then is this apparent contradiction is a "real apparent contradiction", and not a contradiction just to you? I do not find the Schrodinger Cat states to be "an apparent contradiction" at all! So how do you propose that I explain YOUR apparent contradiction to this phenomenon?

Will the silliness ever end?

Zz.

 

[entropy1]

I do not find the Schrodinger Cat states to be "an apparent contradiction" at all!

So then, I would say, you are saying that the cat actually is in two or more states simultaneously? I am really curious.

(Sorry for the sillyness)

 

[vanhees71]

According to quantum theory a system is in a state, described by a statistical operator. Only that you write a state ket as superposition of two arbitrarily other vectors doesn't mean it is in these two states at the same time. Indeed, the sillyness of popular-pseudoscience textbook writers confusing students of true science, will never end. The problem is that pseudoscience sells better to the public than true science...

 

[A. Neumaier]

the cat actually is in two or more states simultaneously?

Whatever the state the cat is in is, one can determine from it the probabilities of all potential measurement results. That's the meaning of a quantum state - nothing more. If the cat is in a superposition 0.6|dead>+0.8|alive>, say, it means that the probability of finding it dead is 0.6^2=36% and that of finding it alive is 0.8^2=64%. There is nothing strange at all about this.

Making sense of quantum mechanics simply requires to retrain your classical intuition so that it will properly work when applied to quantum situations. Once one has learned this, all strangeness or apparent paradox (unnecesarily magnified by the popular press) is gone. See also the thread https://www.physicsforums.com/threa...is-not-weird-unless-presented-as-such.850860/

 

[Demystifier]

So then, I would say, you are saying that the cat actually is in two or more states simultaneously? I am really curious.

No, the cat is always in one state. Sometimes this is a dead state. Sometimes it is an alive state. In principle, it may even be a sum of dead and alive state. But even the sum is one state. Just like the sum 1+2=3 is one number (number 3), not two numbers (numbers 1 & 2). 3 is not 1 & 2. 3 is 1+2.

 

[entropy1]

No, the cat is always in one state. Sometimes this is a dead state. Sometimes it is an alive state. In principle, it may even be a sum of dead and alive state. But even the sum is one state. Just like the sum 1+2=3 is one number (number 3), not two numbers (numbers 1 & 2). 3 is not 1 & 2. 3 is 1+2.

So, how is being partly alive and partly dead being experienced by the cat then?

 

[Demystifier]

So, how is being partly alive and partly dead being experienced by the cat then?

Nobody knows that. See however
http://arxiv.org/abs/1406.3221

 

[A. Neumaier]

how is being partly alive and partly dead being experienced by the cat then?

Experiencing something would amount to the cat making a measurement of its aliveness. If it can experience the result it will find itself alive. This happens with a certain probability. What's the problem?

 

[entropy1]

The cat would have to make a measurement of its aliveness. If it can experience the result it will find itself alive. What's the problem?

The problem that I perceive, is that an assertion is made by Demystifier that the cat could be in a state that is neither a dead or an alive state. So, unless this state is realized for zero duration, the cat has some experience in time in that state, or the cat really isn't in that superposition! That would be a paradox then in my eyes.

 

[Demystifier]

The problem that I conceive, is that an assertion is made by Demystifier that the cat could be in a state that is neither a dead or an alive state.

Maybe the cat would feel like a zombi.
But I don't think that this question really belongs to physics. In the link I gave, however, there is a related question that can be answered by physics. Essentially, it tells what is it like to be in a superposition of two different positions. And the answer is: When you are in such a superposition, you don't have any information from the outside which could inform you about your position.

 

[Nugatory]

Is there one single interpretation possible without the paradoxes of QM, created by among others superposition, the measurement problem and non-locality?

Yes, of course. Learn the mathematical treatment that you have so so stubbornly resisted for so many posts in so many threads. You will find a coherent and paradox-free theory. You may not like what it says, and you may especially dislike what it doesn't say, but that's a different problem.

 

[A. Neumaier]

unless this state is realized for zero duration, the cat has some experience in time in that state

An experience is a measurement and therefore takes a finite time, after which the state has effectively collapsed. As long the cat experiences something, it is alive. But dying also takes time, and during this time the cat is neither clearly dead nor alive - it is in an intermediate state. Typically, this state would be a complicated mixed state, not a Schroedinger cat state, which is only a caricature of reality. But you can already see that the simple-minded 2-state picture that you have in mind is grossly inappropriate when discussing a real situation rather than a thought experiment.

 

[Demystifier]

What I mean by paradox is 'an apparent contradiction'. So, not really a contraction, but it appears (presents itself) as such.

With that definition, quantum mechanics is, of course, full of paradoxes. But it is not that quantum mechanics presents itself as such. It is that some people present it as such.

 

[Nugatory]

Typically, this state would be a complicated mixed state, not a Schroedinger cat state, which is only a caricature of reality. But you can already see that the simple-minded 2-state picture that you have in mind is grossly inappropriate when discussing a real situation rather than a thought experiment.

This seems like a good note upon which the thread can be closed.
(As always, PM me or any mentor if feel that there is more to say that hasn't already been said).