B Are there any empirical tests for the GRW extension of quantum mechanics?

[DrChinese]

The collapse happens under the context of a parameter.So for example the bigger a system is, the bigger the chance of a collapse is for that.Smaller things have a very, very low chance of collapsing.If we have a big entangled system, that will have a very big chance of collapse.

OK, I can see that objective collapse might not occur often if the parameter was "small" for a single particle. But that essentially means such theories don't explain anything useful in the quantum regime. I thought the whole point was to explain away the need for defining "observer" and "measurement". If it comes back to explaining entangled particle behavior using orthodox quantum definitions in 99% of cases, what's the point?

 

[Question69]

OK, I can see that objective collapse might not occur often if the parameter was "small" for a single particle. But that essentially means such theories don't explain anything useful in the quantum regime. I thought the whole point was to explain away the need for defining "observer" and "measurement". If it comes back to explaining entangled particle behavior using orthodox quantum definitions in 99% of cases, what's the point?

Well, wouldn't it explain those ill-defined terms? An observer here is a system of particles, and the collapse happens because you are a big system that gets entangled to the small system that is in superposition because it's not big enough.

 

[StevieTNZ]

@DrChinese - Even without introducing collapse theories, there have been challenges to the notion of "delayed choice entanglement swapping"* which is what I believe you're describing in post #28. See for example: http://philsci-archive.pitt.edu/10007/1/manuscript_final.pdf

(Egg, M. (2013). Delayed-choice experiments and the metaphysics of entanglement. Foundations of Physics, 43(9), 1124-1135.)

* and I certainly agree, alongside Bernard d'Espagnat, in private email correspondence with me that the Zeilinger et al experiment in 2012 was not delayed choice entanglement swapping. Presumably, entanglement needs to exist between the two pairs to swap, which is actually broken when measured by Alice and Bob first before a bell-state measurement occurs on the other two photons.

 

[vanhees71]

That's interesting, what interpretation do you hold to?

The minimal statistical interpretation, i.e., QT without unnecessary philosophical extensions.

 

[vanhees71]

Even in the interpretations subforum, that question is off limits. All QM interpretations make the same predictions for all experiments, so there is no way of testing by experiment which ones are "true". The interpretations subforum is for discussion of what the different interpretations say, not for expressing opinions about which ones people think are "true". Please refer to the guidelines for the interpretations subforum.

So it's forbidden to discuss about alternative ansatzes like the here discussed objective-collapse postulates?

At least I found it interesting that there is now an ERC grant for an experiment testing such postulates with a challenging experiment about the quantum behavior of massive bodies (which is obviously in reach, because otherwise the grant application wouldn't have been successful, and also this aspect is a side effect of all the gravitational-wave detectors since GEO 600 and now LIGO).

 

[Question69]

The minimal statistical interpretation, i.e., QT without unnecessary philosophical extensions.

So just the Schrodinger equation evolving forever?

 

[vanhees71]

It's just taking the probabilistic interpretation of the quantum state as described with the standard quantum-theoretical postulates, seriously. There's also no "quantum-classical cut", but the classical behavior of macroscopic systems follows by standard quantum-statistical arguments and no collapse as a physical process.

 

[Question69]

It's just taking the probabilistic interpretation of the quantum state as described with the standard quantum-theoretical postulates, seriously. There's also no "quantum-classical cut", but the classical behavior of macroscopic systems follows by standard quantum-statistical arguments and no collapse as a physical process.

It's just taking the probabilistic interpretation of the quantum state as described with the standard quantum-theoretical postulates, seriously. There's also no "quantum-classical cut", but the classical behavior of macroscopic systems follows by standard quantum-statistical arguments and no collapse as a physical process.

Yeah, you would get many worlds out of that unless you say the WF is nomological, but that would mean taking superposition as nomological too.

 

[DrChinese]

@DrChinese - Even without introducing collapse theories, there have been challenges to the notion of "delayed choice entanglement swapping"* which is what I believe you're describing in post #28. See for example: http://philsci-archive.pitt.edu/10007/1/manuscript_final.pdf

(Egg, M. (2013). Delayed-choice experiments and the metaphysics of entanglement. Foundations of Physics, 43(9), 1124-1135.)

* and I certainly agree, alongside Bernard d'Espagnat, in private email correspondence with me that the Zeilinger et al experiment in 2012 was not delayed choice entanglement swapping. Presumably, entanglement needs to exist between the two pairs to swap, which is actually broken when measured by Alice and Bob first before a bell-state measurement occurs on the other two photons.

First, I was not referring to the delayed choice branch of the swapping scenario. I am demonstrating that the ordinary time sequencing of collapse in this Bell test scenario cannot be explained by objective collapse theories (which is what this thread is about). In any Bell test, and especially one in which there has been no prior interaction of Alice and Bob particles: It is the final measurement context - and only that final context - which is relevant. Had collapse occurred before that point, the statistics would NOT match the quantum predictions, period.

Second, I vehemently disagree that delayed swapping is not swapping. There is absolutely no detectable difference in the outcomes or the quantum predictions. Of course you can optionally characterize the situation in a different light if it is the delayed choice branch. That being that the perfect correlations of the "outer" 2 photons "causes" the inner 2 photons to acquire the appropriate Bell State. But to me, that is jumping through hoops to preserve causality - and bypassing the obvious explanation (that time ordering is irrelevant).

I did learn something interesting about GRW: "Recall that as in Bohmian mechanics, there is no local beable of spin in [GRW] theory." That from another of Egg's 2013 papers, which I consider a terrible defense of the GRW theory as relates to Bell (spoiler alert: it's all hand waving).

https://arxiv.org/abs/1312.2801

 

[StevieTNZ]

Second, I vehemently disagree that delayed swapping is not swapping.

I happen to agree the experiment shows entanglement swapping, only if Alice and Bob's first 'measurement' (which is just entanglement of the photon with the apparatus) does not cause wave function collapse. It then becomes entanglement swapping between two apparatus and two photons. Otherwise, if entanglement is gone by Alice and Bob's measurement first, what is there to swap? As William Wootters emailed me, you need entanglement in order to swap it.

 

[DrChinese]

I happen to agree the experiment shows entanglement swapping, only if Alice and Bob's first 'measurement' (which is just entanglement of the photon with the apparatus) does not cause wave function collapse. It then becomes entanglement swapping between two apparatus and two photons. Otherwise, if entanglement is gone by Alice and Bob's measurement first, what is there to swap? As William Wootters emailed me, you need entanglement in order to swap it.

Yay, we agree (at least halfway)!

If you require time ordered action, then (not surprisingly) you “prove” there is causality. You might notice the circular logic at play. Amazingly, all explanations work equally well without the added assumption of causality.

On the other hand, the statistical predictions in any Bell test do not depend on any kind of time ordering. The only thing that matters is the final irreversible context. Take from that what you will. I don’t dispute that the experiments can be interpreted in different ways. But it certainly seems awkward to say that perfect correlations at any of an infinite number of possible angle settings cast the system into a Bell suitable state, rather than the other way around.

And I certainly don’t intend to drag this thread away from discussion of Objective Collapse. :) My intention is to learn more about this.

 

[PeterDonis]

So it's forbidden to discuss about alternative ansatzes like the here discussed objective-collapse postulates?

If you have a reference to an objective collapse model that makes different predictions from standard QM, you can give the reference here as a basis for discussion. My statement that you quoted was in reference to interpretations of standard QM, which all make the same experimental predictions.

 

[Question69]

If you have a reference to an objective collapse model that makes different predictions from standard QM, you can give the reference here as a basis for discussion. My statement that you quoted was in reference to interpretations of standard QM, which all make the same experimental predictions.

Here are the models: https://plato.stanford.edu/entries/qm-collapse/

 

[PeterDonis]

Here are the models: https://plato.stanford.edu/entries/qm-collapse/

Do you have any physics references? As in, physics textbooks or peer-reviewed papers? For example, there are some referenced in the SEP article; you should be using those as your primary sources for what the models in question say.

 

[DrChinese]

OK, I can see that objective collapse might not occur often if the parameter was "small" for a single particle. ...

The collapse happens under the context of a parameter.So for example the bigger a system is, the bigger the chance of a collapse is for that.Smaller things have a very, very low chance of collapsing.If we have a big entangled system, that will have a very big chance of collapse.

Upon further review*: I see that the related parameter f is indeed small: 10^−16 per second, which is roughly 1 collapse (localization) every 100 million years (for a single particle). So it basically explains little or nothing in the quantum world, but does explain why we don't see cats that are both dead and alive in the classical world.

I just don't see how this moves the chains on the measurement problem. When does collapse occur when we are in the regime of small quantum systems? We still have all of the usual issues! Not to mention a long time to wait...*This information obtained from the Stanford Plato site referenced in post #43 above.

 

[vanhees71]

Do you have any physics references? As in, physics textbooks or peer-reviewed papers? For example, there are some referenced in the SEP article; you should be using those as your primary sources for what the models in question say.

https://books.google.de/books/about...ton&hl=en&newbks=1&newbks_redir=1&redir_esc=y

Though I don't see any need for nor any empirical hints to such extensions of QT, it's also didcussed by physicists, not only philosophers. In the above book besides to interpretations (Bohm and mny worlds) also one extension (GRW) is discussed. In this latter case one has in principle deviations from the predictions of standard QT, which can be empirically tested in principle.